Patterns of Failure and Clinical Outcomes of Post-operative Buccal Mucosa Cancers Treated with Ipsilateral Radiation Therapy

Abstract

Loco-regional failure in carcinoma buccal mucosa (BM) after radical resection and adjuvant radiotherapy (RT) generally entails a bad prognosis. Usually, adjuvant RT (if indicated), is delivered to tumor bed and bilateral neck nodes. However, selected patients could be treated with ipsilateral RT to tumor bed and neck nodes (IL-RT). Literature on patterns of failure in this group of patients is sparse. We aimed to analyse the failure patterns and survival outcome in these cohort of patients treated at our institute. Eighty patients of post-operative BM cancers treated with IL-RT from June 2013 to May 2017 were included in this retrospective analysis. RT dose was 60-66 Gray in 30-33 fractions over 6-6.5 weeks delivered by linear accelerator using 3-dimensional conformal radiotherapy techniques. All outcomes were evaluated from the time of registration. Local, regional and loco-regional control was defined as time from registration to failure in tumor bed, regional nodes or both, respectively. Disease free survival (DFS) and overall survival (OS) were defined as time from registration to failure at any site (local, regional or distant) and death from any cause, respectively. Kaplan Meier method was used for all outcome analysis. The median age was 45.5 years (range 30-80). Patient characteristics are described in table 1. Median RT completion time and the overall treatment time were 6.2 weeks (range 5.9-7.1) and 11.6 weeks (range 8.5-19), respectively. 62 patients received 60 Gy, one patient 64 Gy and the rest received 66 Gy. The median follow-up time was 24.4 months (range 5-54.2).The 2-year local, regional and loco-regional control rates were 91.9%, 87.6% and 80.5%, respectively. The 2-year DFS and 2-year OS rates were 76.4% and 82.8%, respectively. The crude rates of failures at primary site, ipsilateral and contralateral neck were 12.5%, 12.5% and 3.7%, respectively. All patients with contralateral neck recurrence had N2 disease. Five patients (6.25%) had distant failures. Sixteen patients (20%) died of cancer and 2 patients died of non-malignant causes. The incidence of contralateral recurrence in BM cancer patients treated with primary surgery and adjuvant IL-RT is low. BM cancer with 1-3 risk factors may be treated with IL-RT, except, patients with N2 nodal status, who are at higher risk of contralateral regional recurrence.Abstract MO_23_2678; Table 1Patient CharacteristicsDistributionGender (Male: Female)75: 5T stage (T1: T2: T3: T4)10%: 43%: 26%: 21%N stage (N0: N1: N2)63%: 19%: 18%Overall TNM stage (I: II: III: IV) (As per AJCC 7th edition)5%: 30%: 23%: 42%Risk factors for post-operative RT (>pT3: pN+: PNI: LVI: Close margins: Tumor thickness)*52: 40: 18: 24: 13: 55Number of risk factors for post-op RT (1: 2: 3: >4)10%: 60%: 17.5%: 12.5%Grade (1: 2: 3)42: 34: 4*The total may not add up to 100% because of presence of multiple factors. Abbreviations: RT=Radiotherapy; PNI=Peri-neural invasion; LVI=Lympho-vascular invasion Open table in a new tab