Pattern of failure after adjuvant radiation therapy in oral cavity cancer patients: Data from tertiary care institute in North India

Abstract Objectives: To review failure patterns in oral cavity squamous cell carcinoma treated with surgery and adjuvant radiation therapy. Materials and Methods: All patients with biopsy-proven stage I-IVB oral cavity squamous cell carcinoma (OCSCC) treated with surgery and adjuvant therapy between 2018 and 2022 were evaluated. Outcome measures were 3-years loco-regional recurrence (LRR), overall survival (OS), and progression free survival (PFS). LRR was spatially localized in relation to contour and dose distribution. Results: A total of 85 patients treated between years 2018 to 2022 were evaluated with median follow-up of 19 months. Disease subsites were oral tongue (37.6%) and bucco-alveolar complex (62.4%). Of a total of 25.9% failures, 16/85 (18.8%) were local, 9/85 (10.6%) were regional, 18/85 (21.2%) were locoregional, and 10/85 (11.8%) were distant. For LRR, total in-field failure was 11.8%, marginal failure was 4.7%, and out-of-field failure was seen in 2.4% cases. The 3-year actuarial local, regional control, and LRR in our study were 69%, 84%, and 67%, respectively. The cumulative rates of OS were 72% and PFS was 56%. On univariate analysis, independent factors for local failure were perineural invasion (PNI) (OR = 5.89, P = 0.03), lymph vascular space invasion (LVI) (OR = 3.69, P = 0.05), and pathological N3 (OR = 3.69, P = 0.02). For regional, failure was PNI (OR = 4.53, P = 0.038). For locoregional, failure was PNI (OR = 6.13, P = 0.002) and for distant, failure were PNI (OR = 5.80, P = 0.013), pathological N3 (OR = 4.35, P = 0.03) and LVI (OR = 4.66, P = 0.03). On multivariate Cox proportional hazard analysis, for local, failure risk factors were PNI (HR = 4.32, P = 0.01) and pathological N3 (HR = 3.27, P = 0.047), for locoregional, failure was PNI (HR = 4.42, P = 0.006), and for distant, failure was PNI(HR0 = 4.29, P = 0.05). Conclusions: In our cohort of patients, the most common failure was in-field LRR. PNI was significantly associated with local, locoregional, and distant failure on Cox analysis. In addition to PNI, pathological N3 was the cause of local failure.