International Journal of Particle Therapy
Introduction: Select patients with oropharyngeal SCC are candidates for unilateral radiation therapy. We sought to investigate if ipsilateral targeting leads to increased contralateral recurrences. Methods: We queried the PCG database for patients treated with unilateral proton RT for head and neck SCC from 2015 – 2020 at 12 institutions. DICOMs were evaluated to ensure dose delivered matched a unilateral proton treatment plan. Demographic, clinical and pathological, toxicity and dosimetry information were compiled. Results: We found 43 cases treated with unilateral proton RT. 94% (n¼16) of recurrent cases received prior radiation. Oropharyngeal sites included tonsillar fossa (n¼32), and base of tongue (n¼11). 70% (n¼30) of patients underwent concurrent chemotherapy - typically weekly cisplatin. The median dose and BED delivered was 69.96 CGE and 84.00 Gy respectively. Eight (18.6%) patients experienced at least one grade 3 toxicity. With a mean follow-up of 10.6 months (range 0 - 48) the local control rate at 1 year was 90.7%. All locoregional recurrences occurred within the ipsilateral neck; there were no contralateral failures. Distant metastasis developed in 4.6% of cases. For five cases (n¼5), additional dosimetric analyses were performed for centralized review and revealed that ipsilateral level 2 doses were similar, whereas contralateral level 2 doses were higher with photons, mean: 15.4 Gy vs 0.36 CGE, D5%: 24.5 vs 4.62.
Conclusions: Unilateral Proton Beam RT for oropharynx cancer has similar disease control to photon therapy. The dosimetric advantage of proton beam therapy did not result in excess contralateral failures when compared to historical unilateral photon beam radiotherapy series.
Vayntraub A, Quinn T, Chang J, Kalman N, Katz S, Urbanic J, et al. Contralateral control rate with unilateral proton beam radiotherapy for oropharyngeal SCC: a multi-institutional prospective study from the Proton Collaborative Group. Int J Part Ther. 2022 Spring;8(4):105-106.