PURPOSE

To report the early clinical outcomes of combining intensity-modulated radiation therapy (IMRT) and intensity-modulated proton therapy (IMPT) in comparison with IMRT alone in treating oropharynx cancer (OPC) patients.

MATERIALS AND METHODS

The medical records of 148 OPC patients who underwent definitive radiotherapy (RT) with concurrent systemic therapy, from January 2016 till December 2019 at Samsung Medical Center, were retrospectively reviewed. During the 5.5 weeks' RT course, the initial 16 (or 18) fractions were delivered by IMRT in all patients, and the subsequent 12 (or 10) fractions were either by IMRT in 81 patients (IMRT only) or by IMPT in 67 (IMRT/IMPT combination), respectively, based on comparison of adaptive re-plan profiles and availability of equipment. Propensity-score matching (PSM) was done on 76 patients (38 from each group) for comparative analyses.

RESULTS

With the median follow-up of 24.7 months, there was no significant difference in overall survival and progression free survival between groups, both before and after PSM. Before PSM, the IMRT/IMPT combination group experienced grade ≥ 3 acute toxicities less frequently: mucositis in 37.0% and 13.4% ( < 0.001); and analgesic quantification algorithm (AQA) in 37.0% and 19.4% ( = 0.019), respectively. The same trends were observed after PSM: mucositis in 39.5% and 15.8% ( = 0.021); and AQA in 47.4% and 21.1% ( = 0.016), respectively. In multivariate logistic regression, grade ≥ 3 mucositis was significantly less frequent in the IMRT/IMPT combination group, both before and after PSM ( = 0.027 and 0.024, respectively). AQA score ≥ 3 was also less frequent in the IMRT/IMPT combination group, both before and after PSM ( = 0.085 and 0.018, respectively).

CONCLUSIONS

In treating the OPC patients, with comparable early oncologic outcomes, more favorable acute toxicity profiles were achieved following IMRT/IMPT combination than IMRT alone.