Feasibility Trial of Intensity Modulated Proton Therapy to Reduce Toxicity in Anal Cancer Patients

Purpose:The purpose of this trial was to assess the patient and physician-reported toxicity in anal cancer patients undergoing definitive chemoradiation with intensity-modulated proton therapy (IMPT). Methods:Patients with stage II and III anal cancer were treated with IMPT. All patients received 2 cycles of 5-fluorouracil and mitomycin concurrently with radiation. Toxicity was assessed at baseline, weekly during chemoradiation, and in follow-up using physician-graded common terminology criteria for adverse events (CTCAE) v 4.0 and PRO-CTCAE. The primary endpoint was to define point estimates and 95% CI for acute & GE; grade 2/3 gastrointestinal (GI), genitourinary (GU), dermatologic, and hematologic toxicity. The proportion of PRO-CTCAE questions scored & GE;3 for each domain was compared with the baselinse. The proportion of & GE; grade 2 and & GE; grade 3 toxicities were compared with historic intensity-modulated radiotherapy patients treated on RTOG 0529. Results:Fourteen patients were enrolled from 2017 to 2020. Rates of physician-reported GI, GU, dermatologic, and hematologic toxicity were not significantly different between patients treated with IMPT compared with patients treated with intensity-modulated radiotherapy. Rates of patient-reported dermatologic and GU toxicity were low at baseline with a peak at week 6 (91% and 58% PRO-CTCAE items & GE; grade 3, respectively) and normalization to baseline 3 months after IMPT. In contrast, the proportion of high-grade PRO-CTCAE GI scores was 40% at baseline, which persisted through 1-year posttreatment. Conclusions:Clinician-reported toxicity was not improved with IMPT in the context of this underpowered trial. High-grade GI symptoms persisted for 12 months and were similar to baseline. Additional measures are needed to minimize acute and chronic toxicity related to chemoradiation.

Automated summary

The purpose of this trial was to evaluate the toxicity reported by patients and physicians in anal cancer patients undergoing chemoradiation with intensity-modulated proton therapy. The results showed that there was no significant difference in physician-reported gastrointestinal, genitourinary, dermatologic, and hematologic toxicity between patients treated with intensity-modulated proton therapy and those treated with intensity-modulated radiotherapy. However, high-grade gastrointestinal symptoms persisted for 12 months and additional measures are needed to minimize toxicity related to chemoradiation.