Efficacy and safety of FDG-PET for determining target volume during intensity-modulated radiotherapy for head and neck cancer involving the oral level.

PURPOSE: To determine the efficacy and safety of target volume determination by 18F-fluorodeoxyglucose positron emission tomography-computed tomography (PET-CT) for intensity-modulated radiation therapy (IMRT) for locally advanced head and neck squamous cell carcinoma (HNSCC) extending into the oral cavity or oropharynx. METHODS: We prospectively treated 10 consecutive consenting patients with HNSCC using IMRT, with target volumes determined by PET-CT. Gross tumor volume (GTV) and clinical target volume (CTV) at the oral level were determined by two radiation oncologists for CT, magnetic resonance imaging (MRI), and PET-CT. Differences in target volume (GTVPET, GTVCT, GTVMRI, CTVPET, CTVCT, and CTVMRI) for each modality and the interobserver variability of the target volume were evaluated using the Dice similarity coefficient and Hausdorff distance. Clinical outcomes, including acute adverse events (AEs) and local control were evaluated. RESULTS: The mean GTV was smallest for GTVPET, followed by GTVCT and GTVMRI. There was a significant difference between GTVPET and GTVMRI, but not between the other two groups. The interobserver variability of target volume with PET-CT was significantly less than that with CT or MRI for GTV and tended to be less for CTV, but there was no significant difference in CTV between the modalities. Grade ≤ 3 acute dermatitis, mucositis, and dysphagia occurred in 55%, 88%, and 22% of patients, respectively, but no grade 4 AEs were observed. There was no local recurrence at the oral level after a median follow-up period of 37 months (range, 15-55 months). CONCLUSIONS: The results suggest that the target volume determined by PET-CT could safely reduce GTV size and interobserver variability in patients with locally advanced HNSCC extending into the oral cavity or oropharynx undergoing IMRT. Trial registration UMIN, UMIN000033007. Registered 16 jun 2018, https://center6.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000037631.

Radiation Therapy for Sister Mary Joseph's Nodule: A Review.

Purpose: Umbilical metastasis, known as Sister Mary Joseph's nodule (SMJN), is a manifestation of advanced malignant disease. Patients with SMJN usually require supportive care or palliative systemic chemotherapy. However, with the increasing number of older and infirm patients, radiation therapy for SMJN is needed more frequently. Therefore, we conducted this review to provide insights into radiation treatment for this rare condition. Methods and Materials: We searched PubMed on October 16, 2022, and obtained 275 articles that described SMJN or metastatic tumors within or near the umbilicus, as well as 255 case reports or case series (298 patients) and 20 reviews, original articles, or other study types, 1 of which also described a case. Results: The prognosis of patients with SMJN is extremely poor. However, some patients can survive for more than 2 years. The primary organs of the umbilical metastasis are mainly in the gastrointestinal tract, including the stomach, colon, and pancreas. In addition to these organs, the ovaries, uterine corpus, and breasts are the major organs affected in women. Metastasis may be divided into 4 types according to the tumor location and mechanism of the extension: within the umbilicus, not within although existing near or adjacent to the umbilicus, in the umbilical or paraumbilical hernia sac, and iatrogenic disease. Only 7 reports described patients who received radiation therapy in detail. The patients were divided into 2 groups: a relatively long course and high total dose (approximately 45 Gy) group, and a short course and low total dose group. Conclusions: Umbilical metastasis, known as SMJN, is a rare disease and is divided into 4 types based on the location of the disease and extent mechanism. Although the prognosis of the disease is poor, some patients survive for more than 2 years. Only 7 case reports precisely described radiation therapy. Half of the patients were treated with a short course, whereas the other half were treated with relatively high doses of up to 45 Gy.

Edaravone Exerts Protective Effects on Mice Intestinal Injury without Interfering with the Anti-Tumor Effects of Radiation.

The appropriate dosage of edaravone-a radioprotective agent-and its effect on tumors are unknown. This study evaluated the effects of edaravone on intestinal injuries and tumors in mice induced by whole body X-ray irradiation. Small intestinal mucositis was induced in C3H/HeNSlc mice using a single X-ray dose (15 Gy). Edaravone (15, 30, and 100 mg/kg) was administered 30 min before irradiation to evaluate its protective effect. After 3.5 days, the jejunum was removed and the histological changes were evaluated. Next, C3H/HeNSlc mice with squamous cell carcinoma VII tumors were provided the same single X-ray dose and 100 mg/kg edaravone; further, the tumors were immediately induced after irradiation. The tumor cell viability was detected using an in vivo-in vitro colony formation assay. We found that the intestinal colony-forming ability after irradiation was significantly higher in the 100 mg/kg edaravone group than that in the control group. Moreover, the apoptotic cells in the villi immunohistochemically stained with cleaved caspase-3 were significantly lower in the 100 mg/kg edaravone group than in the control group. We found no radioprotective effects of intraperitoneally inoculated edaravone in both hind legs on squamous cell carcinoma VII tumors. These findings suggest that 100 mg/kg edaravone exerts protective effects on small intestinal injuries without interfering with the antitumor effects of radiation.

Dosimetric investigation of whole-brain radiotherapy with helical intensity modulated radiation therapy and volumetric modulated arc therapy for scalp sparing.

Objective: Intensity-modulated radiotherapy (IMRT) is a well-established radiotherapy technique for delivering radiation to cancer with high conformity while sparing the surrounding normal tissue. Two main purposes of this study are: (1) to investigate dose calculation accuracy of helical IMRT (HIMRT) and volumetric-modulated arc therapy (VMAT) on surface region and (2) to evaluate the dosimetric efficacy of HIMRT and VMAT for scalp-sparing in whole brain radiotherapy (WBRT). Methods: First, using a radiochromic film and water-equivalent phantom with three types of boluses (1, 3, 5 mm), calculation/measurement dose agreement at the surface region in the VMAT and HIMRT plans were examined. Then, HIMRT, 6MV-VMAT and 10MV-VMAT with scalp-sparing, and two conventional three-dimensional conformal radiotherapy plans (6MV-3DCRT and 10MV-3DCRT; as reference data) were created for 30 patients with brain metastasis (30 Gy/10 fractions). The mean dose to the scalp and the scalp volume receiving 24 and 30 Gy were compared. Results: The percentage dose differences between the calculation and measurement were within 7%, except for the HIMRT plan at a depth of 1 mm. The averaged mean scalp doses [Gy], V24Gy [%], and V30Gy [%] (1SD) for 6MV-3DCRT, 10MV-3DCRT, HIMRT, 6MV-VMAT, and 10MV-VMAT were [26.6 (1.1), 86.4 (7.3), 13.2 (4.2)], [25.4 (1.0), 77.8 (7.5), 13.2 (4.2)], [23.2 (1.5), 42.8 (19.2), 0.2 (0.5)], [23.6 (1.6), 47.5 (17.9), 1.2 (1.8)], and [22.7 (1.7), 36.4 (17.6), 0.7 (1.1)], respectively. Conclusion: Regarding the dose parameters, HIMRT achieved a lower scalp dose compared with 6MV-VMAT. However, the highest ability to reduce the mean scalp dose was showed in 10MV-VMAT. Advances in knowledge: Scalp-sparing WBRT using HIMRT or VMAT may prevent radiation-induced alopecia in patients with BM.

Development of deep-inspiration breath-hold system that monitors the position of the chest wall using infrared rangefinder.

We conducted a prospective study to quantitatively evaluate the movement of the chest wall to establish the simple and reproducible deep-inspiration breath-hold (DIBH) method. The left nipple position was monitored to confirm the inspiratory state. Planning computed tomography (CT) was performed under DIBH and free-breath. We conducted radiation plans with DIBH and free-breath CT and evaluated organ at risk (OAR) and target doses according to two different plans. The relationship between positioning errors of the chest wall and patient factors was evaluated using univariate analysis and fixed-effects models. Twenty-three patients aged ≤ 60 years were enrolled during January-August 2021; 358 daily radiation treatments were evaluated. The median time of treatment room occupancy was 16 minutes (interquartile range, 14-20). The area of the planning target volume (PTV) surrounded by the 95% isodose line was more extensive in DIBH than in free breathing (71.6% vs 69.5%, P < 0.01), whereas the cardiac and left anterior descending (LAD) artery doses were lower (both P < 0.01). In the fixed-effects model analysis, the occupation time of the treatment room was correlated with positioning error. The difference between the planned and irradiated dose was the largest in the LAD branch of the coronary artery (-2.5 Gy), although the OAR dose decreased owing to positional error. The current DIBH method, wherein a single point on the chest wall is monitored to confirm that the patient is in an inspiratory state, allows radiation to be performed in a short time with a small dose error.

Olfactory Sensations During Radiation Sessions: A Review.

Purpose: During radiation therapy sessions, certain patients may perceive smells, particularly in younger populations. The sense of smell generally does not interrupt treatment; hence, it has attracted limited attention from oncologists worldwide. However, in certain cases, the prevention of smell perception may be necessary when treating pediatric patients. In this regard, this study reviewed previous studies pertaining to this unusual phenomenon of smell perception during radiation sessions. Methods and Materials: A PubMed search using the terms "radi*" AND ("olfaction" OR "odor" OR "smell" OR "phantosmia") was performed, and 9 articles related to this sensation were identified. Furthermore, through the references in these 9 articles, 3 additional related studies were identified. Results: Perception of smell during radiation treatment sessions was first reported in 1989. This phenomenon entails the perception of a pungent, repulsive, and unpleasant smell and is generally only observed in the presence of radiation beams. Occasionally, these smell perceptions are also accompanied by visual and gustatory sensations. Patients complain about this sensation more frequently when their olfactory regions are irradiated. Nevertheless, some patients have also reported experiencing this sensation when these areas are not included in the radiation field. Although the intensity of this sensation is low, intervention is required to prevent it. The cause of this perception remains unclear and requires further investigation. Conclusions: Conclusions: During radiotherapy sessions, certain patients may perceive smells. The cause of this perception remains unclear and requires further investigation.

Comparison of Recurrence Patterns and Salvage Treatments After Definitive Radiotherapy for cT1a and cT1bN0M0 Esophageal Cancer.

Background: Definitive radiotherapy (RT) for stage I esophageal cancer was reported to result in noninferior overall survival (OS) compared with surgery. However, only a few detailed reports of recurrence patterns and subsequent salvage treatments have been published. This study aimed to compare recurrence patterns and subsequent salvage treatments after definitive RT or chemoradiotherapy (CRT) between cT1a and cT1bN0M0 esophageal cancer (EC). Methods: Patients with cT1a or cT1bN0M0 esophageal squamous cell carcinoma who received definitive RT or CRT were included. Survival outcomes, recurrence patterns, and salvage treatments were evaluated. Results: In total, 40 patients with EC receiving RT or CRT were divided into two groups for evaluation: cT1a (20 patients) and cT1b (20 patients) groups. The 3-year OS rates were 83% and 65% (p = 0.06) and the 3-year progression-free survival rates were 68% and 44% (p = 0.15) in the cT1a and cT1b groups, respectively. Among those in the cT1a group, six had local recurrence and two had metachronous recurrence. Seven patients underwent salvage endoscopic submucosal dissection and one patient received argon plasma coagulation treatment. Among those in the cT1b group, six had local recurrence, one had regional recurrence, and one had both. Of these, one underwent salvage endoscopic submucosal dissection, one received photodynamic therapy, three underwent surgery, one received RT, and two received the best supportive care. Compared with the cT1b group, the cT1a group had a higher proportion of patients who underwent endoscopic treatments (p = 0.007). After the endoscopic treatments, no recurrences were observed in both groups. Conclusions: Regional recurrence and distant metastasis were not observed in the cT1a group. A higher proportion of patients in the cT1a group received salvage endoscopic treatments, and their OS tended to be favorable.

Intracranial stereotactic radiotherapy in off-isocenter target with SyncTraX FX4.

PURPOSE: We investigated the localization accuracy of the off-isocenter targets using SyncTraX FX4, a new image registration device. METHODS: In a phantom study, we used a MultiMet-WL Cube with metal targets at different distances from the isocenter. Image registrations were performed with SyncTraX and cone-beam computed tomography (CBCT). Nineteen fields with different gantry, collimator, and couch angles were delivered to each target. Localization errors of the off-isocenter targets were then evaluated. In a clinical study, localization accuracy was evaluated for 32 patients. First, image registration was performed using SyncTraX, and the accuracy of patient positioning was evaluated using CBCT. Next, positioning corrections were performed for intracranial setup errors exceeding the threshold (0.5 mm/0.5°) in each field. Finally, total setup uncertainty was evaluated using CBCT. Differences in dosimetric errors from planned doses between no patient positioning corrections during treatment and positioning corrections with SyncTraX were also evaluated. RESULTS: In the phantom study, the positioning accuracy on targets up to 7 cm from the isocenter was within 1 mm. In the clinical practice, the localization accuracies of SyncTraX were 0.35 ± 0.39 mm, 0.30 ± 0.24 mm, and 0.03 ± 0.27 mm in the lateral, vertical, and longitudinal directions, respectively. Post-treatment setup errors were reduced by correcting intrafractional setup errors with SyncTraX during treatment. Positioning corrections with SyncTraX reduced the maximum dosimetric error from 1.6% to 1.0%. CONCLUSIONS: SyncTraX provides satisfactory localization accuracy for the off-isocenter targets within 7 cm. SyncTraX reduce dosimetric errors caused by intrafractional setup errors during treatment.

Clinical outcomes of definitive radiotherapy for patients with cT1aN0M0 esophageal cancer unsuitable for endoscopic resection and surgery.

Background: Studies on the clinical outcomes of radiotherapy for clinical (c)T1aN0M0 (UICC-TNM Classification, Eighth Edition) esophageal cancer (EC) are limited. Therefore, this retrospective study aimed to clarify the clinical outcomes of definitive radiotherapy (RT) or chemoradiotherapy (CRT) for cT1aN0M0 EC unsuitable for endoscopic resection and surgery. Methods: Patients with cT1aN0M0 esophageal squamous cell carcinoma who underwent definitive RT or CRT between January 2009 and December 2020 were retrospectively reviewed. The initial response, toxicities, survival rates, recurrence patterns, and salvage treatments of the patients were evaluated. Initial response was measured using the Response Evaluation Criteria in Solid Tumors guideline. Toxicity was assessed and documented following the National Cancer Institute Common Terminology Criteria for Adverse Events (CTCAE) version 5.0. Survival rates from the date of initiation of treatment were measured using the Kaplan-Meier method. Results: Twenty patients treated with definitive RT or CRT were included in the study. The median follow-up duration was 55 months (range, 13-131 months). All patients achieved complete response to the initial treatment. Grade 3 acute toxicities observed esophagitis (10%), pneumonitis (5%), and leukopenia (5%). Late toxicities higher than grade 3 were not observed. The 1-, 3-, and 5-year overall and disease-specific survival rates were 100% and 100%, 83% and 100%, and 67% and 100%, respectively. No treatment-related deaths occurred. Among the 20 patients, 6 showed local recurrence and 2 showed metachronous recurrence. Seven patients underwent salvage endoscopic submucosal dissection (ESD), and one underwent argon plasma coagulation treatment. After the endoscopic treatment, no recurrences were observed. Conclusions: Definitive RT or CRT was considered an alternative initial treatment for patients with cT1aN0M0 EC who were unsuitable for endoscopic resection and surgery.

Improving the accuracy of motion quantification using area detector computed tomography for real-time tumor-tracking irradiation in stereotactic ablative radiotherapy.

CyberKnife radiotherapy enables tumor-tracking irradiation using positional information regarding the tumor and a fiducial marker in a patient's body. This positional information acts as a surrogate of tumor motion. Therefore, deviations in these movements should be quantitatively estimated and included as an internal margin for radiation treatment planning. This study aimed to investigate variations between the positions of fiducial markers and tumor regions using 320-row area detector computed tomography and to analyze the effectiveness of our proposed method in contouring tumor regions based on the fiducial marker position. To determine the moving tumor volume, a typical single-phase image was selected, and pixel values in other phase images were accumulated. Moreover, a maximum-intensity projection image was created to clarify motion deviations in the tumor volume. To evaluate the delineation accuracy, the dice similarity coefficient and mean distance to agreement were calculated in phase-selected and breath-holding computed tomography. Moving chest phantom images were acquired using helical scanning 4-dimensional computed tomography (H-4DCT) and volumetric scanning 4-dimensional computed tomography (V-4DCT), and the delineation accuracies were compared for each scanning type. The average dice similarity coefficient and mean distance to agreement were degraded in limited-phase images, which cannot represent the hysteretic motion of a tumor. Moreover, deviations in tumor volume with unstable motion reached 71.6% in H-4DCT but only 1.6% in V-4DCT. Our proposed method with V-4DCT using area detector computed tomography can achieve accurate moving tumor delineation and can clarify positional associations between the fiducial marker and tumor under respiratory motion.

Case of papillary thyroid cancer presenting with an inoperable cervical mass successfully treated with high-dose radiation therapy.

External-beam radiation therapy (EBRT) for differentiated thyroid cancer has been controversial. Palliative irradiation is usually recommended for patients with treatment-resistant relapse and/or distant metastases, but high-dose EBRT is not often indicated in this situation. A 50-year-old man had treatment-resistant recurrence of an inoperable cervical mass and multiple lung metastases after total thyroidectomy and neck dissection. Because the patient had good performance status and no other life-threatening metastases, he received high-dose intensity-modulated radiation therapy (IMRT). Remarkably, the tumour shrank during treatment. After 3 months, he had bleeding from the internal carotid artery. The bleeding was outside the high-dose irradiation site and was likely due to infection; emergency interventional radiology was performed. The post-EBRT clinical course was favourable and the cervical mass almost disappeared. The patient remained alive for 3 years post treatment. It is possible to extend the indication of high-dose intensity-IMRT in selected patients with differentiated thyroid cancer.

Radiologic criteria of retropharyngeal lymph node metastasis in maxillary sinus cancer.

OBJECTIVE: To determine the most appropriate radiologic criteria of metastatic retropharyngeal lymph nodes (RLNs) in patients with maxillary sinus cancer (MSC). MATERIALS AND METHODS: We retrospectively evaluated 16 consecutive patients who underwent magnetic resonance imaging (MRI) before and after the treatment of locally advanced squamous cell carcinoma of the maxillary sinus. The minimal and maximal diameters of all RLNS were recorded. RLNs were classified as metastatic on the basis of the MRI follow-up (f/u). RLNs were considered non-metastatic if stable disease continued until the final MRI f/u and metastatic in cases with different evaluations (complete response, partial response, progressive disease) determined using Response Evaluation Criteria in Solid Tumours (RECIST) ver. 1.1. The receiver operating characteristic curve (ROC) and area under the curve (AUC) were used to assess the accuracy of various criteria in the diagnosis of metastatic RLNs. RESULTS: Of the 34 RLNs in 16 cases observed on pretreatment MRI, 7 were classified as metastatic RLNs and 27 as non-metastatic RLNs. Using the radiologic criteria, metastatic RLNs tended to be diagnosed more accurately with the minimal axial diameter than with the maximal axial diameter (AUC; 0.97 vs. 0.73, p = 0.06). The most accurate size criterion of metastatic RLNs was a minimal axial diameter of 5 mm or larger, with an accuracy of 94.1% (32 of 34). CONCLUSIONS: The most appropriate radiologic criterion of metastatic RLNs in MSC is a minimal axial diameter of 5 mm or longer.

Unresectable bulky chest wall recurrent breast cancer controlled with CT-guided interstitial high-dose-rate brachytherapy and external beam radiotherapy with adjuvant hormonal therapy - case report.

PURPOSE: Bulky chest wall recurrence after mastectomy presents a therapeutic challenge because of high-dose of radiation required to control the disease, and its proximity to low-tolerance organs at risk. We report a case of successful computed tomography (CT)-guided high-dose-rate (HDR) salvage interstitial brachytherapy (ISBT) boost. MATERIAL AND METHODS: A 70-year-old female initially presented with a tumor in right breast, and was treated with mastectomy and adjuvant chemotherapy, followed by hormonal therapy for 5 years without adjuvant radiotherapy. In 2018, 20 years after the initial treatment, she developed unresectable chest wall recurrence that measured 10.5 cm × 7.3 cm × 4.5 cm, with bone and parietal pleura invasion. Biopsy revealed invasive pleomorphic lobular carcinoma [estrogen receptor (ER)-positive, progesterone receptor (PR)-negative, HER2-negative]. There was no evidence of metastatic disease. RESULTS: The patient underwent external beam radiotherapy (EBRT) plus ISBT. After EBRT of 50 Gy in 25 fractions was completed, CT-guided ISBT was performed as an outpatient treatment. HDR dose was 16 Gy delivered in 2 fractions with 2 implants. Dose was prescribed to gross tumor volume. ISBT plans were created using inverse planning simulated annealing (IPSA) algorithm. Gross tumor volume D90% plus EBRT dose was 82 Gy equivalent dose of 2 Gy (EQD2), assuming α/ß of 4 for breast carcinoma. The patient continued on hormonal therapy. At the 30-month follow-up, the patient remains in remission. The tumor could not be detected by magnetic resonance imaging (MRI) or positron emission tomography (PET). There were no severe treatment-related complications. CONCLUSIONS: CT-guided HDR ISBT boost can be a useful modality in individualizing treatment strategies for breast cancer patients with unresectable bulky chest wall recurrence.

Intrafraction stability using full head mask for brain stereotactic radiotherapy.

PURPOSE: We investigated the immobilization accuracy of a new type of thermoplastic mask-the Double Shell Positioning System (DSPS)-in terms of geometry and dose delivery. METHODS: Thirty-one consecutive patients with 1-5 brain metastases treated with stereotactic radiotherapy (SRT) were selected and divided into two groups. Patients were divided into two groups. One group of patients was immobilized by the DSPS (n = 9). Another group of patients was immobilized by a combination of the DSPS and a mouthpiece (n = 22). Patient repositioning was performed with cone beam computed tomography (CBCT) and six-degree of freedom couch. Additionally, CBCT images were acquired before and after treatment. Registration errors were analyzed with off-line review. The inter- and intrafractional setup errors, and planning target volume (PTV) margin were also calculated. Delivered doses were calculated by shifting the isocenter according to inter- and intrafractional setup errors. Dose differences of GTV D99% were compared between planned and delivered doses against the modified PTV margin of 1 mm. RESULTS: Interfractional setup errors associated with the mouthpiece group were significantly smaller than the translation errors in another group (p = 0.03). Intrafractional setup errors for the two groups were almost the same in all directions. PTV margins were 0.89 mm, 0.75 mm, and 0.90 mm for the DSPS combined with the mouthpiece in lateral, vertical, and longitudinal directions, respectively. Similarly, PTV margins were 1.20 mm, 0.72 mm, and 1.37 mm for the DSPS in the lateral, vertical, and longitudinal directions, respectively. Dose differences between planned and delivered doses were small enough to be within 1% for both groups. CONCLUSIONS: The geometric and dosimetric assessments revealed that the DSPS provides sufficient immobilization accuracy. Higher accuracy can be expected when the immobilization is combined with the use of a mouthpiece.

Radiosensitization using hydrogen peroxide in patients with cervical cancer.

The purpose of the present study was to analyze the feasibility and safety of radiosensitization using hydrogen peroxide for cervical cancer. In superficial tumors, breast cancer and hepatocellular carcinoma, the safety and effectiveness of radiosensitization has been reported; to the best of our knowledge, however, there are no reports on cervical cancer. A total of 20 patients with cervical cancer were recruited. Inclusion criteria were as follows: Patients who required radical external beam radiotherapy (RT); ineligible for or refused brachytherapy; age, ≥20 years; no hematogenous metastasis; Eastern Cooperative Oncology Group Performance Status up to 2; and had not undergone prior treatment. Hydrogen peroxide was used twice a week in combination with RT. A 3% hydrogen peroxide solution-soaked gauze was inserted into the vagina during RT. A total of 45 Gy was delivered in 25 fractions to the whole pelvis with a boost of 10 Gy in 5 fractions if pelvic or para-aortic metastatic lymph nodes were observed. Ultimately, 18 patients were evaluated. Among the 17 patients (excluding one patient with tumor in situ), the one- and two-year overall survival rates were both 90% in patients with stage I/II and 86% in stage III/IV cervical cancer. The adverse events were well tolerated with no severe acute or late adverse events. Although limited by small sample size, short observation time and low radiation dose, the present study demonstrated that radiosensitization treatment may be an option for patients who cannot undergo brachytherapy. The study was retrospectively registered at the university hospital medical information network center (no. UMIN000039045) on January 6, 2020.

Investigation of clinical target volume segmentation for whole breast irradiation using three-dimensional convolutional neural networks with gradient-weighted class activation mapping.

This study aims to implement three-dimensional convolutional neural networks (3D-CNN) for clinical target volume (CTV) segmentation for whole breast irradiation and investigate the focus of 3D-CNNs during decision-making using gradient-weighted class activation mapping (Grad-CAM). A 3D-UNet CNN was adopted to conduct automatic segmentation of the CTV for breast cancer. The 3D-UNet was trained using three datasets of left-, right-, and both left- and right-sided breast cancer patients. Segmentation accuracy was evaluated using the Dice similarity coefficient (DSC). Grad-CAM was applied to trained CNNs. The DSCs for the datasets of the left-, right-, and both left- and right-sided breasts were on an average 0.88, 0.89, and 0.85, respectively. The Grad-CAM heatmaps showed that the 3D-UNet used for segmentation determined the CTV region from the target-side breast tissue and by referring to the opposite-side breast. Although the size of the dataset was limited, DSC ≥ 0.85 was achieved for the segmentation of breast CTV using the 3D-UNet. Grad-CAM indicates the applicable scope and limitations of using a CNN by indicating the focus of such networks during decision-making.

The effects of rotational setup errors in total body irradiation using helical tomotherapy.

PURPOSE: Helical tomotherapy (HT) is a form of intensity-modulated radiation therapy that is employed in total body irradiation (TBI). Because TBI targets the whole body, accurate setup positioning at the edge of the treatment volume is made difficult by the whole-body rotational posture. The purpose of this study is to clarify the tolerance for rotational setup error (SE) in the vertical direction. In addition, we perform a retrospective analysis of actually irradiated dose distributions using previous patients' irradiation data. METHODS: To clarify the effects of rotational SE on the dose distribution, the planned CT images of 10 patients were rotated by 1-5° in the vertical (pitch) direction to create a pseudo-rotational SE image. Then, the effect of the magnitude of the rotational SE on the dose distribution was simulated. In addition, the irradiated dose to the patients was analyzed by obtaining recalculated dose distributions using megavoltage CT images acquired before treatment. RESULTS: The simulation results showed that the average value of the lung volume receiving at least 10 Gy did not exceed the allowable value when the SE value was ≤2°. When the rotational SE was ≤3°, it was possible to maintain the clinical target volume dose heterogeneity within ±10% of the prescribed dose, which is acceptable according to the guidelines. A retrospective analysis of previous patients' irradiation data showed their daily irradiation dose distribution. The dose to the clinical target volume was reduced by up to 3.4% as a result of the residual rotational SE. Although whole-course retrospective analyses showed a statistically significant increase in high-dose areas, the increase was only approximately 1.0%. CONCLUSIONS: Dose errors induced by rotational SEs of ≤2° were acceptable in this study.

Dosimetric predictors of nephrotoxicity in patients receiving extended-field radiation therapy for gynecologic cancer.

PURPOSE: We sought dosimetric predictors of a decreasing estimated glomerular filtration rate (eGFR) in gynecological oncology patients receiving extended-field radiation therapy (EFRT). MATERIALS AND METHODS: Between July 2012 and April 2020, 98 consecutive cervical or endometrial cancer patients underwent EFRT or whole-pelvis radiation therapy (WPRT) with concurrent cisplatin chemotherapy in our institution. To explore the effect of concurrent cisplatin chemotherapy on renal function, the renal function of the WPRT patients was examined. Of the 98 patients, 34 cervical or endometrial cancer patients underwent EFRT including extended-field intensity-modulated radiation therapy (EF-IMRT) and 64 cervical cancer patients underwent WPRT with cisplatin. Of the 34 EFRT patients, 32 underwent concurrent cisplatin chemotherapy. Excluding patients exhibiting recurrences within 6 months, 31 EFRT patients were analyzed in terms of the dose-volume kidney histograms (the percentages of kidney volumes receiving 12, 16, 20, and 24 Gy) and the post- to pre-treatment eGFR ratios. We calculated Pearson correlation coefficients between the renal dose volume and the percentage eGFR reductions of the 31 EFRT patients, and those treated via EF-IMRT. Renal dose constraint significance was evaluated using the Mann-Whitney U test. RESULTS: The eGFR value after WPRT with cisplatin remained largely unchanged for 12 months, unlike that after EFRT. In EFRT patients, a strong correlation was evident between the KV20Gy dose and the post- to pre-treatment eGFR ratio (correlation coefficients - 0.80 for all patients and - 0.74 for EF-IMRT patients). In EF-IMRT patients, the kidney volume receiving 20 Gy tended to correlate negatively with the eGFR reduction. The Mann-Whitney U test showed that patients with KV20Gy values < 10% retained significantly better renal function than did patients with KV20Gy values > 10% (P = 0.002). CONCLUSIONS: Imposition of a severe kidney dose constraint during EF-IMRT may reduce nephrotic toxicity. Future prospective investigations of kidney-sparing EF-IMRT are required.