Clinical factors predicting the outcome of salvage radiotherapy for patients with biochemical recurrence after radical prostatectomy.

BACKGROUND: It remains unclear which patients with biochemical recurrence after prostatectomy are most suitable for salvage radiotherapy. We evaluated the parameters related to outcomes. METHODS: We retrospectively evaluated patients who underwent salvage therapy for biochemical recurrence after prostatectomy between 2005 and 2019. This study aimed to evaluate biochemical recurrence-free survival (bRFS) after salvage radiotherapy and elucidate the parameters associated with bRFS. The bRFS rate was calculated using the Kaplan-Meier method, and the parameters associated with bRFS were evaluated using Cox regression analysis. RESULTS: This study included 67 patients treated with salvage radiotherapy with a median age of 67 years at salvage radiotherapy. The median follow-up period after salvage radiotherapy was 7.3 years. The 5-year bRFS rate following salvage radiotherapy was 47.1%. Univariate analysis showed that PSA doubling time < 6 months, positive surgical margin, and pathological Gleason score ≥ 8 were significantly associated with shorter bRFS (p < 0.001, p = 0.036, p = 0.047, respectively). Multivariable analysis showed that a PSA doubling time < 6 months and positive surgical margins were significantly associated with shorter bRFS (p = 0.001 and p = 0.018, respectively). No serious adverse events were observed. CONCLUSIONS: In our hospital, approximately half of the patients are under long-term control with salvage radiotherapy. A PSA doubling time of < 6 months and positive surgical margins were suggested to be associated with poor outcomes of salvage radiotherapy.

Impact of prostate position-based image-guidance in intensity-modulated radiation therapy for localized prostate cancer.

BACKGROUND/PURPOSE: The long-term clinical impact of prostate position-based image-guided radiotherapy (IGRT) for localized prostate cancer remains unclear. MATERIALS AND METHODS: We retrospectively compared clinical outcomes following intensity-modulated radiation therapy (IMRT) with cone-beam computed tomography-based prostate position-based IGRT (P-IGRT) or without P-IGRT (non-P-IGRT). From June 2011, we applied P-IGRT in IMRT for intermediate-risk (IR) prostate cancer (PCa) (D'Amico risk classification) (76 Gy in 38 fractions, with smaller margins). Clinical outcomes of patients who received P-IGRT between June 2011 and June 2019 were retrospectively compared with those of patients with IR PCa who received IMRT without P-IGRT between October 2002 and May 2011 in our institution (74 Gy in 37 fractions). RESULTS: A total of 222 consecutive patients were analyzed: 114 in the P-IGRT cohort and 108 in the non-P-IGRT cohort. The median follow-up period after IMRT was 7.1 years for the P-IGRT cohort and 10.8 years for the non-P-IGRT cohort. The biochemical failure-free rate was significantly better in the P-IGRT cohort (94.9% for the P-IGRT cohort vs 82.7% for the non-P-IGRT cohort at 10 years, p = 0.041). The rate of rectal bleeding which needs intervention including the use of suppositories was significantly lower in the P-IGRT cohort (p < 0.001). CONCLUSIONS: The use of P-IGRT with higher doses and smaller margins was correlated with significantly better biochemical control, and a lower incidence of rectal bleeding in IMRT for intermediate-risk prostate cancer. The enhanced accuracy using P-IGRT has the potential to independently improve disease control and reduce late rectal bleeding.

Dosimetric verification of four dose calculation algorithms for spine stereotactic body radiotherapy.

The applications of Type B [anisotropic analytical algorithm (AAA) and collapsed cone (CC)] and Type C [Acuros XB (AXB) and photon Monte Carlo (PMC)] dose calculation algorithms in spine stereotactic body radiotherapy (SBRT) were evaluated. Water- and bone-equivalent phantoms were combined to evaluate the percentage depth dose and dose profile. Subsequently, 48 consecutive patients with clinical spine SBRT plans were evaluated. All treatment plans were created using AXB in Eclipse. The prescription dose was 24 Gy in two fractions at a 10 MV FFF on TrueBeam. The doses were then recalculated with AAA, CC and PMC while maintaining the AXB-calculated monitor units and beam arrangement. The dose index values obtained using the four dose calculation algorithms were then compared. The AXB and PMC dose distributions agreed with the bone-equivalent phantom measurements (within ±2.0%); the AAA and CC values were higher than those in the bone-equivalent phantom region. For the spine SBRT plans, PMC, AAA and CC were overestimated compared with AXB in terms of the near minimum and maximum doses of the target and organ at risk, respectively; the mean dose difference was within 4.2%, which is equivalent with within 1 Gy. The phantom study showed that the results from AXB and PMC agreed with the measurements within ±2.0%. However, the mean dose difference ranged from 0.5 to 1 Gy in the spine SBRT planning study when the dose calculation algorithms changed. Users should incorporate a clinical introduction that includes an awareness of these differences.

Role of albumin Cys34 redox state in the progression of differentiated thyroid carcinoma and induction of ferroptosis.

Differentiated thyroid cancer (DTC) is the most prevalent endocrine malignancy worldwide and requires effective prognostic markers and therapeutic targets to optimize patient outcomes. This study investigated the potential of human serum albumin (HSA) cysteine-34 (Cys34) redox state as a prognostic indicator and therapeutic avenue for DTC. A retrospective cohort study of 99 patients with DTC undergoing radioactive iodine therapy found that higher concentrations of HSA with the reduced form of Cys34 (i.e., human mercaptalbumin [HMA]) were associated with improved progression-free survival in metastatic DTC. In vitro experiments using a DTC cell line revealed that HMA induced cytotoxic effects by triggering ferroptosis, characterized by lipid peroxidation, intracellular ROS accumulation, and decreased cell viability. Ferroptosis inhibitors rescued cell viability, confirming their role in cytotoxicity. These results implicate the HSA-Cys34 redox state is a promising avenue for precision medicine in DTC, shedding light on the prognostic relevance and therapeutic potential of HMA-induced ferroptosis. They emphasize the opportunity for personalized treatment strategies to advance the management of patients with DTC.

Impact of Long-term Adjuvant Hormonal Therapy in High-dose IMRT for Unfavorable Locally Advanced Prostate Cancer.

BACKGROUND/AIM: The aim of this study was to evaluate the benefit of adding long-term adjuvant hormonal therapy to high-dose intensity-modulated radiation therapy for locally advanced prostate cancer patients with multiple unfavorable risks. PATIENTS AND METHODS: All cT3-4N0M0 prostate cancer patients with Gleason score 8-10 and prostate-specific antigen ≥30 ng/ml who received intensity-modulated radiation therapy to the prostate and seminal vesicle alone (78 Gy in 39 fractions) between September 2000 and June 2017 at our institution were analyzed retrospectively. All patients received short-term neoadjuvant hormonal therapy. Before May 2011, salvage hormonal therapy was initiated when prostate-specific antigen levels exceeded 4.0 ng/ml (early salvage hormonal therapy cohort). In June 2011, 2-year adjuvant hormonal therapy was added (adjuvant hormonal therapy cohort). Clinical outcomes were retrospectively compared using the log-rank test. RESULTS: In total, 88 patients (44 in both cohorts) were analyzed. Median follow-up periods were 10.9 and 6.1 years in early salvage hormonal therapy and adjuvant hormonal therapy cohorts, respectively. No significant difference in overall survival rates was observed (p=0.58). Disease controls were significantly better in the adjuvant hormonal therapy cohort: 95.5 versus 73.6% for castration-resistant prostate cancer-free rate (p=0.04), and 73.6 versus 34.1% for biochemical failure-free rate (p<0.001), both at 8 years, respectively. CONCLUSION: Among locally advanced prostate cancer patients with multiple unfavorable risks, adding long-term adjuvant hormonal therapy to high-dose intensity-modulated radiation therapy resulted in significantly better disease control than short-term hormonal therapy, even when salvaged early after biochemical failure.

Long-Term Outcomes of a Prospective Study on Highly Hypofractionated Intensity Modulated Radiation Therapy for Localized Prostate Cancer for 3 Weeks.

PURPOSE: Reports of radiation therapy for prostate cancer using dose fractions between moderate hypofractionation and ultrahypofractionation are limited. This pilot study involved the application of highly hypofractionated intensity modulated radiation therapy (IMRT) in 15 fractions for 3 weeks and the number of fractions was intermediate between the 2 previously mentioned dose fractions. The long-term outcomes are reported. METHODS AND MATERIALS: From April 2014 to September 2015, patients with low- to intermediate-risk prostate cancer received 54 Gy in 15 fractions (3.6 Gy per fraction) for 3 weeks using IMRT without intraprostatic fiducial markers or a rectal hydrogel spacer. Neoadjuvant hormone therapy (HT) was administered for 4 to 8 months. Adjuvant HT was not administered to any patients. Rates of biochemical relapse-free survival, clinical relapse-free survival, overall survival, and the cumulative incidence of late grade ≥2 toxicities were analyzed. RESULTS: Twenty-five patients were enrolled in this prospective study; 24 of them were treated with highly hypofractionated IMRT (17% had low-risk and 83% had intermediate-risk disease). The median neoadjuvant HT duration was 5.3 months. The median follow-up period was 77 months (range, 57-87 months). Biochemical relapse-free survival, clinical relapse-free survival, and overall survival rates were 91.7%, 95.8%, and 95.8% at 5 years, and 87.5%, 86.3%, and 95.8% at 7 years, respectively. Neither grade ≥2 late gastrointestinal toxicity nor grade ≥3 late genitourinary toxicity was observed. The cumulative incidence rates of grade 2 genitourinary toxicity were 8.5% and 18.3% at 5 and 7 years, respectively. CONCLUSIONS: Highly hypofractionated IMRT delivering 54 Gy in 15 fractions for 3 weeks for prostate cancer without intraprostatic fiducial markers facilitated favorable oncological outcomes without severe complications. This treatment approach may be a possible alternative to moderate hypofractionation, but further validation is needed.

Recurrence-free survival and prognosis after adjuvant therapy with radioactive iodine-131 in patients with differentiated thyroid carcinoma.

This study aimed to assess recurrence-free survival (RFS) rates and recurrence-related factors of patients who received adjuvant therapy (AT) with radioactive iodine (RAI) for differentiated thyroid cancer (DTC) following thyroidectomy. We evaluated 284 patients who underwent AT between January 2011 and July 2020 at our hospital. Recurrence was defined as visible recurrent lesions on image analysis or need for repeat surgery with pathologically confirmed recurrent lesions. RFS rate and prognostic factors were statistically evaluated. The median observation period was 30.2 months (range, 5.7-294 months). Overall, 192 patients were female and 92 were male, and the median age was 54 years (range, 9-85 years). Initial assessment revealed 39 recurrence cases. The 3-year RFS rate was 85.8% (95% confidence interval: 81.1-90.9%). Univariate analysis revealed that histology (except for papillary carcinoma), Tg level > 4 ng/dL before AT, and AT result significantly exacerbated the RFS rate. In multivariate analysis, histology and AT result were also important contributors to the worsening RFS rate. Results of AT can be determined relatively early and are important in predicting future recurrence in patients with DTC. Increasing the success rate of AT may lead to an improved prognosis.

Quantification of six-degree-of-freedom motion during beam delivery in spine stereotactic body radiotherapy using intra-irradiation cone-beam computed tomography imaging technique.

PURPOSE: Quantifying intra-fractional six-degree-of-freedom (6DoF) residual errors or motion from approved patient setups is necessary for accurate beam delivery in spine stereotactic body radiotherapy. However, previously reported errors were not acquired during beam delivery. Therefore, we aimed to quantify the 6DoF residual errors and motions during arc beam delivery using a concurrent cone-beam computed tomography (CBCT) imaging technique, intra-irradiation CBCT. METHODS: Consecutive 15 patients, 19 plans for various treatment sites, and 199 CBCT images were analyzed. Pre-irradiation CBCT was performed to verify shifts from the initial patient setup using the ExacTrac system. During beam delivery by two or three co-planar full-arc rotations, CBCT imaging was performed concurrently. Subsequently, an intra-irradiation CBCT image was reconstructed. Pre- and intra-irradiation CBCT images were rigidly registered to a planning CT image based on the bone to quantify 6DoF residual errors. RESULTS: 6DoF residual errors quantified using pre- and intra-irradiation CBCTs were within 2.0 mm/2.0°, except for one measurement. The mean elapsed time (mean ± standard deviation [min:sec]) after pre-irradiation CBCT to the end of the last arc beam delivery was 6:08 ± 1:25 and 7:54 ± 2:14 for the 2- and 3-arc plans, respectively. Root mean squares of residual errors for several directions showed significant differences; however, they were within 1.0 mm/1.0°. Time-dependent analysis revealed that the residual errors tended to increase with elapsed time. CONCLUSION: The errors represent the optimal intra-fractional error compared with those acquired using the pre-, inter-beam, and post-6DoF image guidance and can be acquired within a standard treatment timeslot.

Efficacy and Tolerability of Second-line Pembrolizumab With Radiation Therapy in Advanced Urothelial Carcinoma.

BACKGROUND/AIM: Considering the limited data available on immune checkpoint inhibitors and radiation combination therapy in advanced urothelial carcinoma, this study evaluated the survival benefit and associated toxicity of adding radiation therapy to second-line pembrolizumab. PATIENTS AND METHODS: We retrospectively examined 24 consecutive patients with advanced bladder or upper urinary tract urothelial carcinoma and for whom second-line pembrolizumab was initiated between August 2018 and October 2021 in combination with radiation therapy (with curative intent in 12 patients, and palliative intent in 12 patients). Their survival outcomes and toxicities were compared with those of propensity-score-matched cohorts from a Japanese multicenter study with similar characteristics who received pembrolizumab monotherapy. RESULTS: The median follow-up periods after pembrolizumab initiation were 15 months for the curative cohort and 4 months for the palliative cohort. The median overall survival was 27.7 months for the curative cohort and 4.8 months for the palliative cohort. Compared with the matched pembrolizumab monotherapy cohort, overall survival was better among the curative cohort although not statistically significant (p=0.13), but similar between the palliative and matched pembrolizumab monotherapy cohorts (p=0.44). There was no difference in the incidence of grade ≥2 adverse events between the combination and monotherapy cohorts, irrespective of the intent of radiation therapy. CONCLUSION: The combination of radiation therapy and pembrolizumab can be performed with a clinically acceptable safety profile, and the addition of radiation therapy to immune checkpoint inhibitors may improve survival outcome after pembrolizumab treatment in cases where the intent of radiation therapy is curative.

Radiotherapy for ductal carcinoma of the prostate: an analysis based on the Japanese radiation oncology study group survey.

BACKGROUND: The clinical characteristics of prostate ductal carcinoma is still unclear, and treatment strategy has not yet been established due to its rarity. Therefore, we conducted a multicenter survey of radiation therapy for prostate ductal carcinoma in Japan. METHOD: Data of patients with ductal carcinoma of the prostate treated with radiation therapy between 1996 and 2018 were extracted from the database of each facility. RESULTS: Fifty-two treatment records of 41 patients were collected from nine institutions. The treatment purpose and situations were varied curative intent to palliation. Twenty-eight patients received curative treatments. The median follow-up period of these patients was 68 months. Androgen deprivation therapy was combined with radiation therapy in 26 cases (93%). X-ray and particle irradiation was used. Radiation dose range was 63-78 Gy; 5-year overall survival, progression-free survival and biochemical relapse-free survival were 87.0, 79.3 and 79.3%, respectively. One patient experienced Grade 3 radiation proctitis and one experienced Grade 3 radiation cystitis. There were no Grade 4 or worse adverse events. CONCLUSION: Most patient received similar treatment with adenocarcinoma of prostate, and the clinical results were compatible. For more reliable evidence, further studies are required.

Ten-year outcomes of whole-pelvic intensity-modulated radiation therapy for prostate cancer with regional lymph node metastasis.

BACKGROUND: Management of pelvic node-positive prostate cancer has been challenging and controversial. We conducted a study to evaluate the outcomes of whole-pelvic (WP) simultaneous integrated boost (SIB) intensity-modulated radiation therapy (IMRT) combined with androgen deprivation therapy (ADT). METHODS: A total of 67 consecutive patients with cT1c-4N1M0 prostate cancer were definitively treated by WP SIB-IMRT. Neoadjuvant ADT (median: 8.3 months) was administered in all cases. WP SIB-IMRT was designed to simultaneously deliver 78, 66.3, and 58.5 Gy in 39 fractions to the prostate plus seminal vesicles, metastatic lymph nodes (LNs), and the pelvic LN region, respectively. Adjuvant ADT (median: 24.7 months) was administered in 66 patients. RESULTS: The median follow-up period was 81.6 months (range: 30.5-160.7). Biochemical relapse-free, overall, and prostate cancer-specific survival rates at 10 years were 59.8%, 79.6%, and 86.3%, respectively. Loco-regional recurrence was not observed. Being in International Society of Urological Pathology grade group 5 and having a posttreatment detectable nadir prostate-specific antigen (PSA) level (≥0.010 ng/ml) were significantly associated with worse prostate cancer-specific survival and progression of castration resistance. The 10-year cumulative incidence rates of grade 2 and 3 late toxicities were, respectively, 1.5% and 0% for genitourinary, 0% and 1.5% for gastrointestinal events. No grade 4 acute or late toxicities were observed. CONCLUSIONS: WP SIB-IMRT can be safely administered to patients with pelvic node-positive prostate cancer. Since grade group 5 and detectable nadir PSA levels are risks for castration resistance, we may need to increase the intensity of treatment for such cases.

Clinical significance of IDC-P as predictive factor after intensity-modulated radiation therapy.

The clinical significance of intraductal carcinoma of the prostate (IDC-P) in men with nonmetastatic prostate cancer (PCa) treated with high-dose external-beam radiation therapy remains unclear. The aim of this study was to evaluate the impact of IDC-P in men who received intensity-modulated radiation therapy (IMRT) for nonmetastatic PCa. All patients with high-risk (H-R) and very high-risk (VH-R) PCa who received IMRT between September 2000 and December 2013 at our institution were analyzed retrospectively. We re-reviewed biopsy cores for the presence of IDC-P. Treatment consisted of IMRT (median: 78 Gy at 2 Gy per fraction) plus 6-month neoadjuvant hormonal therapy (HT). In total, 154 consecutive patients with H-R and VH-R PCa were analyzed. Intraductal carcinoma of the prostate was present in 27.9% (n = 43). The median follow-up period was 8.4 years. The 10-year PCa-specific survival, biochemical failure (BF), clinical failure, and castration-resistant PCa rates were 90.0%, 47.8%, 27.5%, and 24.5% in patients with IDC-P, and 96.6%, 32.6%, 10.8%, and 7.0% in those without IDC-P, respectively (p = 0.12, 0.04, 0.0031, and 0.012, respectively). In multivariable analysis, IDC-P was not identified as an independent predictive factor for BF (p = 0.26). The presence of IDC-P was correlated with a significantly higher incidence of disease progression in men with H-R and VH-R PCa who received IMRT, although it was not identified as an independent predictive factor for BF. Further investigations are needed to determine the significance of IDC-P as an independent predictive factor for survival outcomes.

Intensity-modulated radiation therapy for prostate cancer after rectal surgery: a single hospital long-term safety analysis.

BACKGROUND: Radiotherapy is a treatment option for prostate cancer patients after rectal surgery; however, the toxicity profile of radiotherapy for such patients has not been elucidated. This study aimed to evaluate the long-term toxicities and efficacy of intensity-modulated radiotherapy (IMRT) in patients with prostate cancer who had undergone rectal surgery. METHODS: We retrospectively analyzed patients with prostate cancer after rectal surgery, who were definitively treated with IMRT between January 2000 and December 2019 at our institution. The planned total dose was 70-78 Gy in 2-Gy fraction, and the dose to the rectal anastomosis was limited to 70 Gy. The acute and late toxicities and survival outcomes were evaluated. RESULTS: Twenty patients were included in the analysis. The median age was 71 years, with a median follow-up of 86 months. The median time from surgery to IMRT was 93.5 months. The median prostate-specific antigen value was 13.17 ng/ml. The median total dose was 74 Gy, and the median maximum dose to rectal anastomosis was 66.97 Gy. The 8-year biochemical recurrence-free and overall survival rates were 70.2% and 90.0%, respectively. The incidence rates of grade 2 acute genitourinary and gastrointestinal toxicities were 14.3% and 0%, respectively. No grade ≥ 3 acute or late toxicities were observed when the rectal anastomosis dose was limited to 70 Gy. CONCLUSIONS: This retrospective analysis suggested that IMRT for patients with prostate cancer after rectal surgery may be safe and effective with rectal dose constraint of Dmax < 70 Gy if more than 5 years have passed after surgery.

Detection efficacy of PET/CT with 18F-FSU-880 in patients with suspected recurrent prostate cancer: a prospective single-center study.

PURPOSE: Our objective was to investigate the efficacy of PET/CT with a novel prostate-specific membrane antigen (PSMA)-targeted PET probe, 18F-FSU-880, for detection and localization of recurrent disease in prostate cancer patients in whom recurrence was suspected based on an increase in plasma prostate-specific antigen (PSA) levels after initial treatment. METHODS: This study was a prospective institutional review board-approved study of 72 patients (age 56-84 years, PSA level 0.22-40.00 ng/ml) with suspected relapse of prostate cancer after primary therapy, including radical prostatectomy (RP) (n = 35) or radiation therapy (RT) (n = 37). Patients underwent PET/CT approximately 1 h and 3 h after injection of 18F-FSU-880 (101.8-380 MBq). The correlation between patient-based detection rate and Gleason score (GS) of the primary tumor and plasma PSA levels at the time of PET/CT was evaluated. Maximum standardized uptake values (SUVmax) of the positive uptakes at 1 h post-injection were compared with those at 3 h post-injection. RESULTS: In total, 51 patients (71%) showed at least one positive PSMA PET result. The PSA-stratified detection rates were 22% (2/9), 36% (4/11), 89% (16/18) and 85% (29/34) for PSA levels of 0.2 to < 0.5, 0.5 to < 1.0, 1.0 to < 2.0 and ≥ 2.0 ng/ml, respectively. The GS-stratified detection rates were 33% (2/6), 67% (16/24), 70% (16/23) and 89% (17/19) for GS 6, 7, 8 and 9, respectively. In lesion-based analysis, 157 positive lesions were detected at 3 h post-injection, 18 in the prostate or prostate bed, 65 in lymph nodes, 71 in the bone and 3 in the lung. Two local recurrences, eight pelvic lymph nodes and one distant lymph node were depicted only at 3 h post-injection. SUV max at 3 h post-injection was significantly higher than SUVmax at 1 h post-injection (p < 0.001). CONCLUSION: Our preliminary data suggest that 18F-FSU-880 might be a promising new PSMA-targeting tracer for detecting recurrence after initial treatment in patients with prostate cancer.

Development of a plan complexity mitigation algorithm based on gamma passing rate predictions for volumetric-modulated arc therapy.

BACKGROUND AND PURPOSE: Volumetric-modulated arc therapy (VMAT) is a complex rotational therapy technique in which highly conformal dose distribution can be realized by varying the speed of gantry rotation, multileaf collimator (MLC) shape, and dose rate. However, the complexity of the technique creates a discrepancy between the calculated and measured doses. Thus, to mitigate the plan complexity in VMAT, this study aimed to develop an algorithm and evaluate its usefulness by conducting a feasibility study. MATERIALS AND METHODS: A total of 50 patients who underwent VMAT between September 2015 and December 2020 were arbitrarily selected for this study. Specifically, patients with less than 85% gamma passing rate (GPR) at 5%/1 mm or 3%/2 mm criterion were selected randomly. Using the GPR prediction model, problematic MLC positions that contribute to a decrease in GPR were identified. Those problematic MLC positions were optimized using a limited nonlinear algorithm under mechanical limitations. Additionally, the dose prescription for the target was re-normalized. The VMAT modulated complexity score (MCSv ), averaged aperture area (AA), and monitor unit per gray (MU/Gy) were evaluated as plan complexity parameters. Calculated doses in patient geometry were evaluated for the target and its surrounding region. In addition, an ArcCHECK cylindrical diode array was used to measure the dose, and GPRs at 5%/1 mm and 3%/2 mm criteria were evaluated to analyze the difference between the mitigated and original plans. The difference was calculated using the mean ± standard deviation. RESULTS: The differences between the MCSv , AA, and MU/cGy values for the mitigated and original plans were 0.8 ± 1.7 (×10-2 ), 42.7 ± 57.9, and -5.6 ± 8.5, respectively. Regarding the calculated dose, the dose volume parameters were consistent within 1% for the target and the surrounding region. The differences between the mitigated and original plans were 1.8 ± 2.9% and 1.3 ± 1.8% for GPRs at 5%/1 mm and 3%/2 mm, respectively. CONCLUSIONS: This feasibility study resulted in the development of an algorithm with the potential to mitigate plan complexity and improve the GPR for VMAT under minor leaf position modifications.

Highly hypofractionated intensity-modulated radiation therapy for nonmetastatic prostate cancer with a simultaneous integrated boost to intraprostatic lesions: a planning study.

PURPOSE: The purpose of this planning study was to develop an acceptable technique for highly hypofractionated intensity-modulated radiation therapy using simultaneous integrated boost technique (SIB-hHF-RT) for nonmetastatic National Comprehensive Cancer Network high-risk prostate cancer. MATERIALS AND METHODS: We created SIB-hHF-RT plans for 14 nonmetastatic prostate cancer patients with MRI-detectable intraprostatic lesions (IPLs) and without intestines locating close to the seminal vesicle and prostate. We prescribed 57 Gy for IPLs and 54 Gy for the remainder of planning target volume (PTV) in 15 fractions. The IPLs were contoured based on magnetic resonance imaging, and PTV was generated by adding 6-8-mm margins to the clinical target volume. For the dose-volume constraints of organs at risk (OARs), the same constraints as 54 Gy plans were used so as not to increase the toxicity. RESULTS: All created plans fulfilled the dose-volume constraints of all targets and OARs. The median estimated beam-on time was 108.5 s. For patient-specific quality assurance, the global gamma passing rates (3%/2 mm) with 10% dose threshold criteria were greater than 93% in all cases and greater than 95% in 11 cases. CONCLUSION: SIB-hHF-RT plans were developed that fulfill the acceptable dose-volume constraints and pass patient-specific quality assurance. We believe these plans can be applied to selected patients with nonmetastatic prostate cancer.

Comparison between planar and single-photon computed tomography images for radiation intensity quantification in iodine-131 scintigraphy.

This study aimed to evaluate the feasibility of quantifying iodine-131 (131I) accumulation in scintigraphy images and compare planar and single-photon emission computed tomography (SPECT) images to estimate 131I radioactivity in patients receiving radioactive iodine therapy for thyroid cancer. We evaluated 72 sets of planar and SPECT images acquired between February 2017 and December 2018. Simultaneously, we placed a reference 131I capsule next to the patient during image acquisition. We evaluated the correlation between the intensity of the capsule in the images and the capsule dose and estimated the radiation dose at the thyroid bed. The mean capsule dose was 2.14 MBq (range, 0.63-4.31 MBq). The correlation coefficients (p-value) between capsule dose and maximum and mean intensities in both planar and SPECT images were 0.93 (p < 0.01), 0.96 (p < 0.01), 0.60 (p < 0.01), and 0.47 (p < 0.01), respectively. The mean intensities of planar images show the highest correlation coefficients. Based on a regression equation, the average radiation dose in the thyroid bed was 5.9 MBq. In conclusion, planar images reflected the radiation dose more accurately than SPECT images. The regression equation allows to determine the dose in other regions, such as the thyroid bed or sites of distant metastasis.

Long-term safety of high-dose whole pelvic IMRT for high-risk localized prostate cancer through 10-year follow-up.

BACKGROUND: The aim of this study was to evaluate the long-term efficacy and safety of whole pelvic intensity-modulated radiation therapy with a simultaneous-integrated boost (WP-SIB-IMRT) for locally advanced prostate cancer (LAPCa). METHODS: All patients with cT3-4N0M0 prostate cancer treated with WP-SIB-IMRT between February 2006 and September 2009 at our institution were analyzed retrospectively. The prescribed dose was 78 Gy to the prostate and 58.5 Gy to the prophylactic pelvic lymph nodal area in 39 fractions delivered using the simultaneous-integrated boost technique. All patients received short-term neoadjuvant androgen-deprivation therapy alone (median 8.3 months). Propensity-score matching (PSM) analysis was performed to evaluate the additional benefit of prophylactic whole pelvic radiation therapy (WPRT), using the cohort of 203 LAPCa patients treated with prostate-only IMRT (PO-IMRT). RESULTS: In total, 47 consecutive patients were analyzed. The median estimated risk of pelvic lymph node involvement was 57.5%. The median follow-up period was 10.5 years. The 10 year prostate cancer-specific survival and biochemical failure (BF) rates were 92.2 and 54.8%, respectively. The 10 year cumulative incidence rates of ≥ grade 2 late genitourinary and gastrointestinal toxicities were 21.6 and 17.2%, respectively. From a total of 250 patients, PSM analysis identified 76 patients with similar characteristics, and no significant difference in BF rates was observed between WP-SIB-IMRT and PO-IMRT cohorts (p = 0.261). CONCLUSIONS: WP-SIB-IMRT for LAPCa was safe over long-term observation, although no clear benefit of WPRT was observed among our small and highly selected cohort. Regarding the additional efficacy of WPRT, further investigations are needed.

Reducing variability among treatment machines using knowledge-based planning for head and neck, pancreatic, and rectal cancer.

PURPOSE: This study aimed to assess dosimetric indices of RapidPlan model-based plans for different energies (6, 8, 10, and 15 MV; 6- and 10-MV flattening filter-free), multileaf collimator (MLC) types (Millennium 120, High Definition 120, dual-layer MLC), and disease sites (head and neck, pancreatic, and rectal cancer) and compare these parameters with those of clinical plans. METHODS: RapidPlan models in the Eclipse version 15.6 were used with the data of 28, 42, and 20 patients with head and neck, pancreatic, and rectal cancer, respectively. RapidPlan models of head and neck, pancreatic, and rectal cancer were created for TrueBeam STx (High Definition 120) with 6 MV, TrueBeam STx with 10-MV flattening filter-free, and Clinac iX (Millennium 120) with 15 MV, respectively. The models were used to create volumetric-modulated arc therapy plans for a 10-patient test dataset using all energy and MLC types at all disease sites. The Holm test was used to compare multiple dosimetric indices in different treatment machines and energy types. RESULTS: The dosimetric indices for planning target volume and organs at risk in RapidPlan model-based plans were comparable to those in the clinical plan. Furthermore, no dose difference was observed among the RapidPlan models. The variability among RapidPlan models was consistent regardless of the treatment machines, MLC types, and energy. CONCLUSIONS: Dosimetric indices of RapidPlan model-based plans appear to be comparable to the ones based on clinical plans regardless of energies, MLC types, and disease sites. The results suggest that the RapidPlan model can generate treatment plans independent of the type of treatment machine.