RESUMO
PURPOSE: While intensity modulated proton therapy can deliver simultaneous integrated boost (SIB) to the dominant intraprostatic lesion (DIL) with high precision, it is sensitive to anatomic changes. We investigated the dosimetric effects from these changes based on pretreatment cone-beam computed tomographic (CBCT) images and identified the most important factors using a multilayer perceptron neural network (MLPNN). METHODS AND MATERIALS: DILs were contoured based on coregistered multiparametric magnetic resonance images for 25 previously treated prostate cancer patients. SIB plans were created with (1) prostate clinical target volume - V70 Gy = 98%; (2) DIL - V98 Gy > 95%; and (3) all organs at risk (OARs)"?> within clinical constraints. SIB plans were applied to daily CBCT-based deformed planning computed tomography (CT)"?>. DIL - V98 Gy, bladder/rectum maximum dose (Dmax) and volume changes, femur shifts, and the distance from DIL to organs at riskOARs"?> in both planning computed tomogramsCT"?> and CBCT were calculated. Wilcoxon signed-ranks tests were used to compare the changes. MLPNNs were used to model the change in ΔDIL - V98 Gy > 10% and bladder/rectum Dmax > 80 Gy, and the relative importance factors for the model were provided. The performances of the models were evaluated with receiver operating characteristic curves. RESULTS: Comparing initial plan to the average from evaluation plans, respectively, DIL - V98 Gy was 89.3% ± 19.9% versus 86.2% ± 21.3% (P = .151); bladder Dmax 71.9 ± 0.6 Gy versus 74.5 ± 2.9 Gy (P < .001); and rectum Dmax 70.1 ± 2.4 Gy versus 74.9 ± 9.1Gy (P = .007). Bladder and rectal volumes were 99.6% ± 39.5% and 112.8% ± 27.2%, respectively, of their initial volume. The femur shift was 3.16 ± 2.52 mm. In the modeling of ΔDIL V98 Gy > 10%, DIL to rectum distance changes, DIL to bladder distance changes, and rectum volume changes ratio are the 3 most important factors. The areas under the receiver operating characteristic curves were 0.89, 1.00, and 0.99 for the modeling of ΔDIL - V98 Gy > 10%, and bladder and rectum Dmax > 80 Gy, respectively. CONCLUSIONS: Dosimetric changes in DIL SIB with intensity modulated proton therapy can be modeled and classified based on anatomic changes on pretreatment images by an MLPNN.
RESUMO
PURPOSE: For muscle-invasive bladder cancer, bladder preserving chemoradiotherapy (BPCRT) has shown to be a viable alternative for patients with urothelial carcinoma (UCa). Traditionally bladder cancer with variant histology UCa or other tumors types involving the bladder have worse outcomes and BPCRT has been contraindicated. However, there is limited high level evidence for this recommendation. MATERIALS/METHODS: The National Cancer Database (NCDB) was queried for all patients with Bladder cancer treated from 2004 to 2015 restricted to clinical stage T2-4, N0, M0 who had variants of UCa or other tumors types involving the bladder (e.g. adenocarcinoma and squamous cell carcinoma). Only patients treated with definitive intent with either radical cystectomy or BPCRT after maximal transurethral tumor resection were analyzed. Propensity-score matching was used. RESULTS: 356 patients had BPCRT and 2093 patients had definitive surgery for muscle-invasive bladder cancer limited to variants of UCa and other tumors types involving the bladder. On multivariable analysis worse prognosis was associated with age >65 years old (HR 1.24, p = 0.004) and T4 disease (HR 1.90, p < 0.001). In propensity score weighted sample, there was no statistical significant difference in OS for patients with BPCRT as compared to cystectomy (p = 0.387) and for neuroendocrine, micropapillary or not otherwise specified histology subgroups there was no significant difference. Patients with adenocarcinoma (HR 1.75) or squamous cell carcinoma (HR 1.49) had worse OS associated with BPCRT compared to surgery. CONCLUSION: From 2004 to 2015, BPCRT in muscle-invasive bladder cancer was associated with similar overall survival compared to cystectomy in patients with selected variant histology but with worse OS for adenocarcinoma or squamous cell carcinoma specifically. As our study has inherent limitations, these hypotheses require validation in a prospective setting and/or with a larger sample size.