Correlation between patients' anatomical characteristics and interfractional internal prostate motion during intensity modulated radiation therapy for prostate cancer.

Intensity modulated radiation therapy (IMRT) is one of a standard treatment for localized prostate cancer. Although lower complication is expected for smaller target margin, determination of optimal margin is important. For bony-structure based registration, internal prostate motion is the main factor determining the margin from clinical target volume to planning target volume. The purpose of this study was to measure interfractional internal motion of the prostate and to identity the factors which enlarge or reduce the margin, with special focus on patients' anatomical characteristics. The 586 image sets of 16 patients acquired with megavoltage cone beam computed tomography were analyzed. For each patient, prostate shift in three directions was recorded for each fraction to calculate the required margin. Correlations between these values and patients' anatomical characteristics were evaluated. The posteriorly required margin correlated positively with rectal volume and rectal mean area (p = 0.015 and p = 0.008), while random error in lateral, craniocaudal and anteroposterior direction correlated negatively (p = 0.014, 0.04 and 0.0026, respectively) with body mass index (BMI). In addition to the previously identified factor of distended rectum, BMI was newly identified as another significant factor influencing interfractional internal prostate motion.

Reirradiation using high-dose-rate interstitial brachytherapy for locally recurrent cervical cancer: a single institutional experience.

OBJECTIVES: This study aimed to evaluate the effectiveness and feasibility of reirradiation using high-dose-rate interstitial brachytherapy (HDR-ISBT) in patients with recurrent cervical cancer. METHODS: The records of 52 consecutive women with central pelvic recurrence who were salvaged with HDR-ISBT-based reirradiation were retrospectively reviewed. Data regarding the primary disease, follow-up findings, recurrence, the treatment outcome, and toxicities were collected. Multivariate analysis was performed using the Cox proportional hazards regression model to identify predictors of the response to HDR-ISBT. Survival rate was calculated using the Kaplan-Meier method and compared using the log-rank test. RESULTS: A total of 52 patients who had been treated with HDR-ISBT-based reirradiation were included in our database. The local control rate was 76.9% (40/52), and the median postrecurrence survival period was 32 months. Grade 3 or 4 late toxicities were observed in 13 patients (25%). Multivariate analysis revealed that tumor size and the treatment-free interval were significant poor prognostic factors of postrecurrence survival. In a comparison between the patients who were salvaged with HDR-ISBT-based reirradiation (ISBT group) and those who were treated with palliative therapy alone (palliative group), we found that among the patients who displayed 0 or 1 poor prognostic factors, the patients in the ISBT group survived significantly longer than those in the palliative group. In contrast, similar survival rates were seen in both groups among the patients with 2 or more poor prognostic factors. CONCLUSIONS: Reirradiation using HDR-ISBT is effective and feasible in patients with recurrent cervical cancer. Our 2-clinical variable prognostic model might enable physicians to identify patients who would not derive clinical benefit from HDR-ISBT and offer them the opportunity to receive other types of treatment.

Estimation of rectal dose using daily megavoltage cone-beam computed tomography and deformable image registration.

PURPOSE: The actual dose delivered to critical organs will differ from the simulated dose because of interfractional organ motion and deformation. Here, we developed a method to estimate the rectal dose in prostate intensity modulated radiation therapy with consideration to interfractional organ motion using daily megavoltage cone-beam computed tomography (MVCBCT). METHODS AND MATERIALS: Under exemption status from our institutional review board, we retrospectively reviewed 231 series of MVCBCT of 8 patients with prostate cancer. On both planning CT (pCT) and MVCBCT images, the rectal contours were delineated and the CT value within the contours was replaced by the mean CT value within the pelvis, with the addition of 100 Hounsfield units. MVCBCT images were rigidly registered to pCT and then nonrigidly registered using B-Spline deformable image registration (DIR) with Velocity AI software. The concordance between the rectal contours on MVCBCT and pCT was evaluated using the Dice similarity coefficient (DSC). The dose distributions normalized for 1 fraction were also deformed and summed to estimate the actual total dose. RESULTS: The DSC of all treatment fractions of 8 patients was improved from 0.75±0.04 (mean ±SD) to 0.90 ±0.02 by DIR. Six patients showed a decrease of the generalized equivalent uniform dose (gEUD) from total dose compared with treatment plans. Although the rectal volume of each treatment fraction did not show any correlation with the change in gEUD (R(2)=0.18±0.13), the displacement of the center of gravity of rectal contours in the anterior-posterior (AP) direction showed an intermediate relationship (R(2)=0.61±0.16). CONCLUSION: We developed a method for evaluation of rectal dose using DIR and MVCBCT images and showed the necessity of DIR for the evaluation of total dose. Displacement of the rectum in the AP direction showed a greater effect on the change in rectal dose compared with the rectal volume.

Dose-volume histogram predictors of chronic gastrointestinal complications after radical hysterectomy and postoperative concurrent nedaplatin-based chemoradiation therapy for early-stage cervical cancer.

PURPOSE: The purpose of this study was to evaluate dose-volume histogram (DVH) predictors for the development of chronic gastrointestinal (GI) complications in cervical cancer patients who underwent radical hysterectomy and postoperative concurrent nedaplatin-based chemoradiation therapy. METHODS AND MATERIALS: This study analyzed 97 patients who underwent postoperative concurrent chemoradiation therapy. The organs at risk that were contoured were the small bowel loops, large bowel loop, and peritoneal cavity. DVH parameters subjected to analysis included the volumes of these organs receiving more than 15, 30, 40, and 45 Gy (V15-V45) and their mean dose. Associations between DVH parameters or clinical factors and the incidence of grade 2 or higher chronic GI complications were evaluated. RESULTS: Of the clinical factors, smoking and low body mass index (BMI) (<22) were significantly associated with grade 2 or higher chronic GI complications. Also, patients with chronic GI complications had significantly greater V15-V45 volumes and higher mean dose of the small bowel loops compared with those without GI complications. In contrast, no parameters for the large bowel loop or peritoneal cavity were significantly associated with GI complications. Results of the receiver operating characteristics (ROC) curve analysis led to the conclusion that V15-V45 of the small bowel loops has high accuracy for prediction of GI complications. Among these parameters, V40 gave the highest area under the ROC curve. Finally, multivariate analysis was performed with V40 of the small bowel loops and 2 other clinical parameters that were judged to be potential risk factors for chronic GI complications: BMI and smoking. Of these 3 parameters, V40 of the small bowel loops and smoking emerged as independent predictors of chronic GI complications. CONCLUSIONS: DVH parameters of the small bowel loops may serve as predictors of grade 2 or higher chronic GI complications after postoperative concurrent nedaplatin-based chemoradiation therapy for early-stage cervical cancer.

Postoperative whole pelvic radiotherapy plus concurrent chemotherapy versus extended-field irradiation for early-stage cervical cancer patients with multiple pelvic lymph node metastases.

OBJECTIVES: The aim of this study was to compare the efficacy of postoperative pelvic radiotherapy plus concurrent chemotherapy with that of extended-field irradiation (EFRT) in patients with FIGO Stage IA2-IIb cervical cancer with multiple pelvic lymph node metastases. METHODS: We retrospectively reviewed the medical records of patients with FIGO Stage IA2-IIb cervical cancer who had undergone radical surgery between April 1997 and March 2008. Of these, 55 patients who demonstrated multiple pelvic lymph node metastases were treated postoperatively with pelvic radiotherapy plus concurrent chemotherapy (n=29) or EFRT (n=26). Thirty-six patients with single pelvic node metastasis were also treated postoperatively with pelvic radiotherapy plus concurrent chemotherapy. The recurrence rate, progression free survival (PFS), and overall survival (OS) were compared between the treatment groups. RESULTS: Pelvic radiotherapy plus concurrent chemotherapy was significantly superior to EFRT with regard to recurrence rate (37.9% vs 69.2%, p=0.0306), PFS (log-rank, p=0.0236), and OS (log-rank, p=0.0279). When the patients were treated with pelvic radiotherapy plus concurrent chemotherapy, there was no significant difference in PFS or OS between the patients with multiple lymph node metastases and those with single node metastases. With regards to grade 3-4 acute or late toxicities, no statistically significant difference was observed between the two treatment groups. CONCLUSIONS: Postoperative pelvic radiotherapy plus concurrent chemotherapy is superior to EFRT for treating patients with FIGO Stage IA2-IIb cervical cancer displaying multiple pelvic lymph node metastases.