The aim of this study was to evaluate the potential to increase the tumor control probability (TCP) with ‘dose painting by numbers’ (DPBN) plans optimized in a treatment planning system (TPS) compa...

Purpose: We report the outcome of hypofractionated proton boost as an alternative to high dose-rate brachytherapy boost, aimed at an equivalent dose exceeding 86 Gy in 2 Gy fractions, for patients with localized prostate cancer and all risk groups. Methods: Proton boost of 20 Gy given in 4 daily fractions to the prostate was followed after a one-week rest by photon therapy to 50 Gy in 2 Gy fractions. Outcomes are presented per risk group according to both NCCN and ISUP classifications. Advanced imaging was performed for adequate staging, and at an early stage of rising PSA, to identify the relapse site. Endpoints were PSA relapse-free-, locoregional relapse-free-, and distant metastasis-free- survival. Prostate cancer-specific-, metastasis-free-, and overall survival were also estimated. Genitourinary (GU) and gastrointestinal (GI) toxicity were based on patients' questionnaires and physicians' records. Results: We treated 531 patients between 2002 and 2015; 504 had localized disease. The cohort included 180 patients with T3/T4 disease (36%). The majority of the 50% with high-/very high-risk disease received ADT, 9-24 months; 92 had adjuvant pelvic node treatment. Median follow-up was 113 months (43-193). For low-, intermediate-, high-, and very high-risk patients, the 5-year PSA relapse-free survival was 100%, 94%, 82%, and 72%, respectively. Prolonged ADT improved biochemical control and nodal treatment regional control. The NCCN classification had higher predictive discrimination than the ISUP classification. The 5-year prevalence grade 3+ was 2% for GU and 0% for GI toxicity in pre-treatment symptom-free patients, and not worsened by nodal treatment. Conclusion: Dose escalation with hypofractionated proton boost was as effective as reported with high dose-rate brachytherapy boost, and the GU and GI toxicity profile was very similar. The proton boost was also appropriate for patients with larger prostate volume, higher T-stage, and high-risk disease encompassing elective regional node photon therapy. (C) 2019 The Authors. Published by Elsevier B.V.

To investigate the feasibility of dose painting by numbers (DPBN) with respect to robustness for proton therapy for head and neck cancers (HNC), and to study the influence of variable RBE on the TCP and OAR dose burden. Data for 19 patients who have been scanned pretreatment with PET-FDG and subsequently treated with photon therapy were used in the study. A dose response model developed for photon therapy was implemented in a TPS, allowing DPBN plans to be created. Conventional homogeneous dose and DPBN plans were created for each patient, optimized with either fixed RBE = 1.1 or a variable RBE model. Robust optimization was used to create clinically acceptable plans. To estimate the maximum potential loss in TCP due to actual SUV variations from the pre-treatment imaging, we applied a test case with randomized SUV distribution. Regardless of the use of variable RBE for optimization or evaluation, a statistically significant increase (p < 0.001) in TCP was found for DPBN plans as compared to homogeneous dose plans. Randomizing the SUV distribution decreased the TCP for all plans. A correlation between TCP increase and variance of the SUV distribution and target volume was also found. DPBN for protons and HNC is feasible and could lead to a TCP gain. Risks associated with the temporal variation of SUV distributions could be mitigated by imposing minimum doses to targets. The correlation found between TCP increase and SUV variance and target volume may be used for patient selection.