Chung, Peter W M

Abstract Background MR‐guided adaptive radiotherapy (ART) allows for daily plan optimization based on patient‐specific anatomy. Accumulated doses, driven by deformable image registration (DIR), of daily fractions can provide cumulative dose metrics and insights into toxicity and tumor control. In prostate ART, inter‐ and intra‐factional deformations, particularly due to bladder and rectum, pose a challenge to accurate DIR generation. Purpose To quantify geometric and dosimetric accuracy of a proposed prostate MR‐to‐MR DIR approach to support MR‐guided ART dose accumulation. Methods We evaluated DIR accuracy in 25 patients treated with 30 Gy in five fractions on a 1.5 T MR‐linac using an adaptive workflow. For all patients, a reference MR was used for planning, with three images collected at each fraction: adapt MR for adaptive planning, verify MR for pretreatment position verification and beam‐on for capturing anatomy during radiation delivery. We assessed three DIR approaches: intensity‐based, intensity‐based with controlling structures (CS), and intensity‐based with controlling structures and points of interest (CS + P). DIRs were performed between the reference and fraction images and within fractions (adapt‐to‐verify and adapt‐to‐beam‐on). For the evaluation, we propagated CTV, bladder, and rectum contours using the DIRs and compared each to manually delineated contours using Dice similarity coefficient, mean distance to agreement, and dose–volume metrics. Results CS and CS + P improved geometric agreement between manual and propagated contours over intensity‐only DIR. For example, mean distance to agreement (DTA mean ) for reference‐to‐beam‐on intensity‐only DIR was 0.131 ± 0.009 cm (CTV), 0.46 ± 0.08 cm (bladder), and 0.154 ± 0.013 cm (rectum). For the CS, the DTA mean values were 0.018 ± 0.002, 0.388 ± 0.14, and 0.036 ± 0.013 cm. Finally, for CS + P, these values were 0.015 ± 0.001, 0.025 ± 0.004, and 0.021 ± 0.002 cm. Dosimetrically, comparing CS and CS + P for reference to beam‐on DIRs resulted in a change of CTV D98% from [−29 cGy, 19 cGy] to [−18 cGy, 26 cGy], bladder D5cc from [−51 cGy, 544 cGy] to [−79 cGy, 36 cGy], and rectum D1cc from [−106 cGy, 72 cGy] to [−52 cGy, 74 cGy]. Conclusion CS improved geometric and dosimetric accuracy over intensity‐only DIR, with CS + P providing further performance improvement, particularly for bladder. However, session image segmentation remains a challenge, which may be addressed with automated contouring.

Hypofractionated radiation therapy regimens should not be used as standard of care for localized soft tissue sarcoma

AbstractBackgroundWe reviewed the disease control and complications of the treatment of sacrococcygeal chordoma from four tertiary cancer centers with emphasis on the effects of radiotherapy in surgically treated patients.MethodsA total of 193 patients with primary sacrococcygeal chordoma from 1990 to 2015 were reviewed. There were 124 males, with a mean age of 59 ± 15 years and a mean follow‐up of 7 ± 4 years. Eighty‐nine patients received radiotherapy with a mean total dose of 61.8 ± 10.9 Gy.ResultsThe 10‐year disease‐free and disease‐specific survival was 58% and 72%, respectively. Radiation was not associated with local recurrence (hazard ratio [HR], 1.13; 95% confidence interval [CI], 0.59‐2.17; P = 0.71), metastases (HR, 0.93; 95% CI, 0.45‐1.91; P = 0.85) or disease‐specific survival (HR, 0.96; 95% CI, 0.46‐2.00; P = 0.91). Higher doses (≥70 Gy; HR, 0.52; 95% CI, 0.20‐1.32; P = 0.17) may be associated with reduced local recurrence. Radiotherapy was associated with wound complications (HR, 2.76; 95% CI, 1.64‐4.82;, P < 0.001) and sacral stress fractures (HR, 4.73; 95% CI, 1.88‐14.38; P < 0.001).ConclusionsIn this multicenter review, radiotherapy was not associated with tumor outcome but associated with complications. The routine use of radiotherapy with en‐bloc resection of sacrococcygeal chordomas should be reconsidered in favor of a selective, individualized approach with a radiation dose of ≥70 Gy.

e16003 Background: Multidisciplinary management improves complex treatment decision making in cancer care, but its impact for bladder cancer (BC) has not been documented. While radical cystectomy (RC) is currently viewed as the standard of care for muscle-invasive bladder cancer (MIBC), radiotherapy-based, bladder-sparing trimodal therapy (TMT) combining transurethral resection of bladder tumor, chemotherapy for radiation sensitization and external beam radiotherapy has emerged as a valid treatment option. In the absence of randomized studies, we compared the oncological outcomes between patients managed by RC or TMT using a propensity-score matched cohort analysis. Methods: Patients seen in our multidisciplinary bladder cancer clinic (MDBCC) from 2008 to 2013 were retrospectively reviewed. Those who received TMT for MIBC were identified and matched (for gender, cT and cN stage, ECOG status, Charlson comorbidity score, treatment date, age, CIS, hydronephrosis) using propensity scores, to patients who underwent RC. Overall survival and disease-specific survival (DSS) were assessed with Cox Proportional hazards modeling and competing risk analysis, respectively. Results: 112 patients with MIBC were included after matching, 56 treated with TMT and 56 by RC. Median age was 68.0 years and 29.5% were cT3/cT4. At a median follow up of 4.51 years, there were 20 (35.7%) deaths (13 from BC) in the RC group and 22 (39.3%) deaths (13 from BC) in the TMT group. 5 year DSS was 73.2% and 76.6%, in the RC and TMT groups, respectively (p = 0.49). Salvage cystectomy was performed in 6/56 TMT patients (10.7%). Conclusions: In the setting of a MDBCC, TMT yielded survival outcomes similar to matched RC patients. Appropriately selected MIBC patients should be offered the opportunity to discuss various treatment options including organ-sparing TMT.