We recently investigated the acute toxicity outcomes for the first 10 patients treated with IMPT for NPC at MD Anderson. In order to get an idea of how toxicities of IMPT compare to the more traditional photon-based IMRT, we conducted a 2:1 case-matched control study. For this study, recently published in the International Journal of Particle Therapy, we matched the 10 patients treated with IMPT with 20 similar patients treated with IMRT based on the size of their tumor, how many lymph nodes were involved, whether or not they received chemotherapy, gender and age. We found that only 20% of patients receiving IMPT required a feeding tube during therapy compared to 65% of those receiving IMRT. We then sought to identify factors associated with whether or not patients needed a feeding tube. Of the factors evaluated, the most significant one was radiation dose to the oral cavity. No patient who received less than 26 Gy mean dose to the oral cavity needed a feeding tube, but all patients receiving more than 41.8 Gy mean dose to the oral cavity did need a feeding tube. On the whole, IMPT was better able to spare the oral cavity from excess radiation dose, and this likely contributes to the lower rates of feeding-tube placement among patients who received IMPT.



A retrospective case-matched control study such as this one is a useful way to compare aspects between two treatments, however, a prospective trial would provide higher quality information on which to base treatment decisions. Due to the low incidence of NPC in the U.S., however, a randomized trial in North America alone is unlikely. Therefore, in collaboration with our colleagues in Asia, we will soon open an international, multicenter prospective trial investigating IMPT for NPC to gather more data on the safety, efficacy and potential benefits of proton therapy for this challenging disease. In the meantime, a prospective, randomized controlled trial is underway comparing IMPT and IMRT in the treatment of oropharyngeal cancer (OPC) as we continue to study the utility of proton therapy to deliver radiation precisely while limiting unnecessary dose to surrounding structures.

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