Intensity-modulated proton therapy versus intensity-modulated photon radiotherapy for locally advanced HPV-positive oropharyngeal squamous cell carcinoma: A systematic review and meta-analysis.

Abstract

e18060 Background: Intensity-modulated proton therapy (IMPT) has been gaining popularity as a method of treating locally advanced HPV positive oropharyngeal squamous cell carcinoma (OPSCC) due to the ability to reduce the amount of normal tissue that is exposed to radiation but whether or not it will result in better clinical outcomes when compared to intensity-modulated photon radiotherapy (IMRT), is still unknown. We performed a meta-analysis to evaluate the effects of IMPT on both cancer related toxicities and outcomes in comparison to IMRT for patients diagnosed with locally advanced HPV positive OPSCC. Methods: We evaluated all comparative studies that examined the use of IMPT vs. IMRT in stage III-IV HPV positive OPSCC. Using random-effects models, we estimated pooled relative risks (RRs) with 95% CIs for each study's measure of association. The primary outcomes of interest were: weight loss; gastrostomy tube insertion; xerostomia; dysphagia; mucositis; fatigue; locoregional recurrence; and OS. Statistical heterogeneity was assessed via I². Results: In total, there were 4 studies that involved 912 patients. As per these studies, a greater number of patients experienced clinically relevant weight loss when receiving IMPT than when receiving IMRT (RR 1.63, 95% CI 1.17–2.27; p= .004; I²= 0%). Additionally, a comparison of six studies which included a total of 1143 patients indicated that gastrostomy tubes are inserted more often after IMPT (RR 2.9, 95% CI 1.8 – 4.6; p<.00001; I²= 0%). No statistically or clinically significant differences were found regarding other side effects from treatments. In terms of cancer recurrence, there was a greater rate of loco-regional recurrence for those patients who received IMPT as compared to IMRT (RR 1.58, 95% CI 1.26- 1.97; p< .0001; I²= 0%) in three studies which included a total of 592 patients. However, no statistical difference in overall survival was identified between IMPT and IMRT (RR 1.06, 95% CI 0.87- 1.29; p=.56), even though there was significant variability (I²= 87%) in three studies which included a total of 747 patients. Conclusions: In locally advanced HPV positive OPSCC, there were no differences in toxicity profiles from IMPT compared to IMRT, and there were increased rates of weight loss, gastrostomy tube placement, and locoregional recurrence from IMPT compared to IMRT, without any observed survival advantage. This highlights the need for future prospective randomized trials to clarify the role of IMPT in the management of locally advanced HPV positive OPSCC.