Acute Toxicities and Short-Term Patient Outcomes After Intensity-Modulated Proton Beam Radiation Therapy or Intensity-Modulated Photon Radiation Therapy for Esophageal Carcinoma: A Mayo Clinic Experience

Purpose: Intensity modulated proton beam radiation therapy (IMPT) has a clinically significant dosimetric advantage over intensity modulated photon radiation therapy (IMRT) for the treatment of patients with esophageal cancer, particularly for sparing the heart and lungs. We compared acute radiation therapy–related toxicities and short-term clinical outcomes of patients with esophageal cancer who received treatment with IMPT or IMRT. Methods and Materials: We retrospectively reviewed the electronic health records of consecutive adult patients with esophageal cancer who underwent concurrent chemoradiotherapy with IMPT or IMRT in the definitive or neoadjuvant setting from January 1, 2014, through June 30, 2018, with additional follow-up data collected through January 31, 2019. Treatment-related toxicities were evaluated per the Common Terminology Criteria for Adverse Events, version 4. Survival outcomes were estimated with the Kaplan-Meier method. Results: A total of 64 patients (32 per group) were included (median follow-up time: 10 months for IMPT patients vs 14 months for IMRT patients). The most common radiation therapy regimen was 45 Gy in 25 fractions, and 80% of patients received a simultaneous integrated boost to a median cumulative dose of 50 Gy. Similar numbers of IMPT patients (n = 15; 47%) and IMRT patients (n = 18; 56%) underwent surgery (P =.07), with no difference in pathologic complete response rates (IMPT: n = 5; 33% vs IMRT: n = 7; 39%; P =.14). At 1 year, the clinical outcomes also were similar for IMPT and IMRT patients, respectively. Local control was 92% versus 84% (P =.87), locoregional control 92% versus 80% (P =.76), distant metastasis–free survival 87% versus 65% (P =.08), progression-free survival 71% versus 45% (P =.15), and overall survival 74% versus 71% (P =.62). The rate of acute treatment–related grade 3 toxicity was similar between the groups (P =.71). Conclusions: In our early experience, IMPT is a safe and effective treatment when administered as part of definitive or trimodality therapy. Longer follow-up is required to evaluate the effectiveness of IMPT.