Low contralateral failure rate with unilateral proton beam radiotherapy for oropharyngeal squamous cell carcinoma: A multi-institutional prospective study from the proton collaborative group.

INTRODUCTION: Unilateral radiation therapy is appropriate for select patients with oropharyngeal squamous cell carcinoma (OPSCC). The use of proton beam therapy (PBT) in the unilateral setting decreases the dose to the contralateral neck and organs at risk. This study aims to evaluate contralateral recurrences in patients who received ipsilateral PBT. METHODS: We evaluated the Proton Collaborative Group database for patients treated with PBT for head and neck squamous cell carcinoma between the years 2015-2020 at 12 institutions. Dosimetric analysis was performed in five cases. RESULTS: Our analysis included 41 patients that received ipsilateral PBT with a mean follow-up of 14.7 months. 37% patients (n = 15) were treated for recurrent disease, and 63% (n = 26) were treated for de novo disease. Oropharyngeal sites included tonsillar fossa (n = 30) and base of tongue (n = 11). The median dose and BED delivered were 69.96 CGE and 84 Gy, respectively. Eight (20%) patients experienced at least one grade 3 dysphagia (n = 4) or esophagitis (n = 4) toxicity. No grade ≥ 4 toxicities were reported. There was one (2.4%) failure in the contralateral neck. The 1-year locoregional control was 88.9% and the freedom from distant metastasis was 95.5% (n = 2). The dosimetric analysis demonstrated similar ipsilateral level II cervical nodal region doses, whereas contralateral doses were higher with photon plans, mean: 15.5 Gy and 0.7CGE, D5%: 25.1 Gy and 6.6CGE. CONCLUSIONS: Our series is the first to report outcomes for patients with OPSCC receiving unilateral PBT. The contralateral neck failure rate was excellent and comparable to failure rates with photon irradiation.

Incidence and patterns of distant metastases for patients with early-stage breast cancer after breast conservation treatment.

BACKGROUND: Breast conservation treatment (BCT), consisting of breast conservation surgery followed by definitive radiation therapy (RT), has been shown to be effective for early-stage breast cancer. Patterns of metastatic failure by specific anatomic site are not well described in the literature. METHODS: A total of 1754 patients with stage I or II invasive carcinoma of the breast treated with BCT between 1977 and 2003 were identified. Patients were scored based on first site of metastasis: bone, brain, lung, liver, or other. Non-breast cancer deaths, contralateral breast cancer, and second malignancies were treated as competing risks events. Cumulative incidence functions for each competing event were calculated using competing risk methodology. Univariate analysis was performed to determine the hazard ratio (HR) associated with patient and tumor characteristics. RESULTS: The most common event was non-breast cancer death (16.5% at 15 years; 95% confidence interval [CI], 13.9%-19.4%). The most common exclusive first site of metastasis was bone (5.9% at 15 years). The 4 most common anatomic sites of distant metastases as the first exclusive event were bone (41.1%), lung (22.4%), liver (7.3%), and brain (7.3%). CONCLUSION: The present study has demonstrated the site-specific risks of metastases. These data support current clinical practice of screening for site-specific metastatic disease after BCT based on concerning patient-specific signs or symptoms.