Contouring variability of human- and deformable-generated contours in radiotherapy for prostate cancer.

This study was designed to evaluate contouring variability of human-and deformable-generated contours on planning CT (PCT) and CBCT for ten patients with low-or intermediate-risk prostate cancer. For each patient in this study, five radiation oncologists contoured the prostate, bladder, and rectum, on one PCT dataset and five CBCT datasets. Consensus contours were generated using the STAPLE method in the CERR software package. Observer contours were compared to consensus contour, and contour metrics (Dice coefficient, Hausdorff distance, Contour Distance, Center-of-Mass [COM] Deviation) were calculated. In addition, the first day CBCT was registered to subsequent CBCT fractions (CBCTn: CBCT2-CBCT5) via B-spline Deformable Image Registration (DIR). Contours were transferred from CBCT1 to CBCTn via the deformation field, and contour metrics were calculated through comparison with consensus contours generated from human contour set. The average contour metrics for prostate contours on PCT and CBCT were as follows: Dice coefficient-0.892 (PCT), 0.872 (CBCT-Human), 0.824 (CBCT-Deformed); Hausdorff distance-4.75 mm (PCT), 5.22 mm (CBCT-Human), 5.94 mm (CBCT-Deformed); Contour Distance (overall contour)-1.41 mm (PCT), 1.66 mm (CBCT-Human), 2.30 mm (CBCT-Deformed); COM Deviation-2.01 mm (PCT), 2.78 mm (CBCT-Human), 3.45 mm (CBCT-Deformed). For human contours on PCT and CBCT, the difference in average Dice coefficient between PCT and CBCT (approx. 2%) and Hausdorff distance (approx. 0.5 mm) was small compared to the variation between observers for each patient (standard deviation in Dice coefficient of 5% and Hausdorff distance of 2.0 mm). However, additional contouring variation was found for the deformable-generated contours (approximately 5.0% decrease in Dice coefficient and 0.7 mm increase in Hausdorff distance relative to human-generated contours on CBCT). Though deformable contours provide a reasonable starting point for contouring on CBCT, we conclude that contours generated with B-Spline DIR require physician review and editing if they are to be used in the clinic.

Characterization of a commercial hybrid iterative and model-based reconstruction algorithm in radiation oncology.

PURPOSE: Iterative reconstruction (IR) reduces noise, thereby allowing dose reduction in computed tomography (CT) while maintaining comparable image quality to filtered back-projection (FBP). This study sought to characterize image quality metrics, delineation, dosimetric assessment, and other aspects necessary to integrate IR into treatment planning. METHODS: CT images (Brilliance Big Bore v3.6, Philips Healthcare) were acquired of several phantoms using 120 kVp and 25-800 mAs. IR was applied at levels corresponding to noise reduction of 0.89-0.55 with respect to FBP. Noise power spectrum (NPS) analysis was used to characterize noise magnitude and texture. CT to electron density (CT-ED) curves were generated over all IR levels. Uniformity as well as spatial and low contrast resolution were quantified using a CATPHAN phantom. Task specific modulation transfer functions (MTF task) were developed to characterize spatial frequency across objects of varied contrast. A prospective dose reduction study was conducted for 14 patients undergoing interfraction CT scans for high-dose rate brachytherapy. Three physicians performed image quality assessment using a six-point grading scale between the normal-dose FBP (reference), low-dose FBP, and low-dose IR scans for the following metrics: image noise, detectability of the vaginal cuff/bladder interface, spatial resolution, texture, segmentation confidence, and overall image quality. Contouring differences between FBP and IR were quantified for the bladder and rectum via overlap indices (OI) and Dice similarity coefficients (DSC). Line profile and region of interest analyses quantified noise and boundary changes. For two subjects, the impact of IR on external beam dose calculation was assessed via gamma analysis and changes in digitally reconstructed radiographs (DRRs) were quantified. RESULTS: NPS showed large reduction in noise magnitude (50%), and a slight spatial frequency shift (∼ 0.1 mm(-1)) with application of IR at L6. No appreciable changes were observed for CT-ED curves between FBP and IR levels [maximum difference ∼ 13 HU for bone (∼ 1% difference)]. For uniformity, differences were ∼ 1 HU between FBP and IR. Spatial resolution was well conserved; the largest MTFtask decrease between FBP and IR levels was 0.08 A.U. No notable changes in low-contrast detectability were observed and CNR increased substantially with IR. For the patient study, qualitative image grading showed low-dose IR was equivalent to or slightly worse than normal dose FBP, and is superior to low-dose FBP (p < 0.001 for noise), although these did not translate to differences in CT number, contouring ability, or dose calculation. The largest CT number discrepancy from FBP occurred at a bone/tissue interface using the most aggressive IR level [-1.2 ± 4.9 HU (range: -17.6-12.5 HU)]. No clinically significant contour differences were found between IR and FBP, with OIs and DSCs ranging from 0.85 to 0.95. Negligible changes in dose calculation were observed. DRRs preserved anatomical detail with <2% difference in intensity from FBP combined with aggressive IRL6. CONCLUSIONS: These results support integrating IR into treatment planning. While slight degradation in edges and shift in texture were observed in phantom, patient results show qualitative image grading, contouring ability, and dosimetric parameters were not adversely affected.

Interval between hysterectomy and start of radiation treatment is predictive of recurrence in patients with endometrial carcinoma.

PURPOSE: Adjuvant radiation therapy (RT) has been shown to improve local control in patients with endometrial carcinoma. We analyzed the impact of the time interval between hysterectomy and RT initiation in patients with endometrial carcinoma. METHODS AND MATERIALS: In this institutional review board-approved study, we identified 308 patients with endometrial carcinoma who received adjuvant RT after hysterectomy. All patients had undergone hysterectomy, oophorectomy, and pelvic and para-aortic lymph node evaluation from 1988 to 2010. Patients' demographics, pathologic features, and treatments were compared. The time interval between hysterectomy and the start of RT was calculated. The effects of time interval on recurrence-free (RFS), disease-specific (DSS), and overall survival (OS) were calculated. Following univariate analysis, multivariate modeling was performed. RESULTS: The median age and follow-up for the study cohort was 65 years and 72 months, respectively. Eighty-five percent of the patients had endometrioid carcinoma. RT was delivered with high-dose-rate brachytherapy alone (29%), pelvic RT alone (20%), or both (51%). Median time interval to start RT was 42 days (range, 21-130 days). A total of 269 patients (74%) started their RT <9 weeks after undergoing hysterectomy (group 1) and 26% started ≥ 9 weeks after surgery (group 2). There were a total of 43 recurrences. Tumor recurrence was significantly associated with treatment delay of ≥ 9 weeks, with 5-year RFS of 90% for group 1 compared to only 39% for group 2 (P<.001). On multivariate analysis, RT delay of ≥ 9 weeks (P<.001), presence of lymphovascular space involvement (P=.001), and higher International Federation of Gynecology and Obstetrics grade (P=.012) were independent predictors of recurrence. In addition, RT delay of ≥ 9 weeks was an independent significant predictor for worse DSS and OS (P=.001 and P=.01, respectively). CONCLUSIONS: Delay in administering adjuvant RT after hysterectomy was associated with worse survival endpoints. Our data suggest that shorter time interval between hysterectomy and start of RT may be beneficial.

Improved survival of baby boomer women with early-stage uterine cancer: A Surveillance, Epidemiology and End Results (SEER) Study.

AIM: To study the prognostic impact of baby boomer (BB) generation on survival end-points of patients with early-stage endometrial carcinoma (EC). PATIENTS AND METHODS: Data were obtained from the SEER registry between 1988-2009. Inclusion criteria included women who underwent hysterectomy for stage I-II EC. Patients were divided into two birth cohorts: BB (women born between 1946 and 1964) and pre-boomers (PB) (born between 1926 and 1945). RESULTS: A total of 30,956 patients were analyzed. Considering that women in the PB group were older than those of the BB generation, the statistical analysis was limited to women 50-59 years of age at the time of diagnosis (n=11,473). Baby boomers had a significantly higher percentage of endometrioid histology (p<0.0001), higher percentage of African American women (p<0.0001), lower tumor grade (p<0.0001), higher number of dissected lymph nodes (LN) (p<0.0001), and less utilization of adjuvant radiation therapy (p=0.0003). Overall survival was improved in women in the BB generation compared to the PB generation (p=0.0003) with a trend for improved uterine cancer-specific survival (p=0.0752). On multivariate analysis, birth cohort (BB vs. PB) was not a significant predictor of survival end-points. Factors predictive of survival included: tumor grade, FIGO stage, African-American race, and increased number of dissected LN. CONCLUSION: Our study suggests that the survival of BB women between 50-60 years of age is better compared to women in the PB generation. As more BB patients are diagnosed with EC, further research is warranted.

A novel approach for establishing benchmark CBCT/CT deformable image registrations in prostate cancer radiotherapy.

Deformable image registration (DIR) is an integral component for adaptive radiation therapy. However, accurate registration between daily cone-beam computed tomography (CBCT) and treatment planning CT is challenging, due to significant daily variations in rectal and bladder fillings as well as the increased noise levels in CBCT images. Another significant challenge is the lack of 'ground-truth' registrations in the clinical setting, which is necessary for quantitative evaluation of various registration algorithms. The aim of this study is to establish benchmark registrations of clinical patient data. Three pairs of CT/CBCT datasets were chosen for this institutional review board approved retrospective study. On each image, in order to reduce the contouring uncertainty, ten independent sets of organs were manually delineated by five physicians. The mean contour set for each image was derived from the ten contours. A set of distinctive points (round natural calcifications and three implanted prostate fiducial markers) were also manually identified. The mean contours and point features were then incorporated as constraints into a B-spline based DIR algorithm. Further, a rigidity penalty was imposed on the femurs and pelvic bones to preserve their rigidity. A piecewise-rigid registration approach was adapted to account for the differences in femur pose and the sliding motion between bones. For each registration, the magnitude of the spatial Jacobian (|JAC|) was calculated to quantify the tissue compression and expansion. Deformation grids and finite-element-model-based unbalanced energy maps were also reviewed visually to evaluate the physical soundness of the resultant deformations. Organ DICE indices (indicating the degree of overlap between registered organs) and residual misalignments of the fiducial landmarks were quantified. Manual organ delineation on CBCT images varied significantly among physicians with overall mean DICE index of only 0.7 among redundant contours. Seminal vesicle contours were found to have the lowest correlation amongst physicians (DICE = 0.5). After DIR, the organ surfaces between CBCT and planning CT were in good alignment with mean DICE indices of 0.9 for prostate, rectum, and bladder, and 0.8 for seminal vesicles. The Jacobian magnitudes |JAC| in the prostate, rectum, and seminal vesicles were in the range of 0.4-1.5, indicating mild compression/expansion. The bladder volume differences were larger between CBCT and CT images with mean |JAC| values of 2.2, 0.7, and 1.0 for three respective patients. Bone deformation was negligible (|JAC| = ∼ 1.0). The difference between corresponding landmark points between CBCT and CT was less than 1.0 mm after DIR. We have presented a novel method of establishing benchmark DIR accuracy between CT and CBCT images in the pelvic region. The method incorporates manually delineated organ surfaces and landmark points as well as pixel similarity in the optimization, while ensuring bone rigidity and avoiding excessive deformation in soft tissue organs. Redundant contouring is necessary to reduce the overall registration uncertainty.

Vaginal cuff dehiscence after vaginal cuff brachytherapy for uterine cancer. A case report.

Vaginal cuff dehiscence is a rare, but potentially serious complication after total hysterectomy. We report a case of vaginal cuff dehiscence after vaginal cuff brachytherapy. A 62 year old female underwent a robotic-assisted laparoscopic hysterectomy with bilateral salpingo-oophorectomy, and was found to have International Federation of Gynecology and Obstetrics (FIGO) 2009 stage IB endometrioid adenocarcinoma of the uterus. The patient was referred for adjuvant vaginal cuff brachytherapy. During the radiation treatment simulation, a computerized tomography (CT) of the pelvis showed abnormal position of the vaginal cylinder. She was found to have vaginal cuff dehiscence that required immediate surgical repair. Vaginal cuff dehiscence triggered by vaginal cuff brachytherapy is very rare with only one case report in the literature.

Endometrial carcinoma in the baby boomer generation. Tumor characteristics and clinical outcome.

BACKGROUND: Baby boomers (BB) entering retirement represent a significant burden on medical resources. The unique lifestyle characteristics engendered by the BB may lead to different endometrial cancer characteristics that bear understanding. We sought to characterize BB with endometrioid carcinoma after hysterectomy and compare the results to those of prior to the baby boomers (PB). PATIENTS AND METHODS: After reviewing our prospectively maintained database of 1,450 patients with endometrial cancer, we identified 595 patients who underwent hysterectomy for 1988 International Federation of Gynecologic Oncology (FIGO) stage I-II uterine endometrioid carcinomas, who were born between 1926 and 1964. Their medical records were reviewed in this Institutional review board (IRB)-approved study. Patients with non-endometrioid carcinoma and those who received preoperative therapy were excluded. Patients were defined as BB (born 1946-1964) or PB (born in 1926-1945). The two groups were compared regarding patients' demographics, tumor characteristics and survival. Following a univariate analysis, multivariable modeling was carried out using Cox regression analysis. RESULTS: All patients underwent hysterectomy with a minimum of two years' follow-up. There were 234 patients (39%) in the BB group and 361 patients (61%) in the PB group. Median follow-up for the study cohort was 56 months. BB had higher body mass index (p=0.027), lower tumor grade (p=0.002), earlier FIGO stage (p=0.023), higher number of dissected lymph nodes (p=0.008), less lymphvascular space involvement (p=<0.034), less utilization of adjuvant therapy (p=<0.001), and younger age at diagnosis (p=0.002). However, there was no significant difference found between the BB and PB in regards to local control, disease-specific survival and overall survival. For the study cohort, FIGO stage and tumor grade were independent predictors of recurrence-free and disease-specific survival. There was a trend towards shorter overall survival for the PB women (p=0.063). CONCLUSION: Although tumor characteristics were more favorable in the BB group of women, local control and survival end-points were not statistically different compared to those of the PB group. As more BB are diagnosed with endometrial carcinoma, further research is warranted to further elucidate the characteristic differences in endometrial carcinoma, if any, in this generation.