Impact of Depth of Invasion Tumor Budding and Worst Pattern of Invasion on Clinical Outcome in Post-Operative Oral Cavity Squamous Cell Carcinoma

Abstract

<h3>Purpose/Objective(s)</h3> Definitive treatment for oral cavity squamous cell carcinoma (OCSCC) is surgery followed by post-operative radiotherapy (PORT) with or without chemotherapy. Risk factors for PORT are T3/T4, node positive, lympho-vascular space invasion (LVI) or perineural invasion (PNI), close margin etc. Depth of invasion (DOI), tumor budding (TB) and worst pattern of invasion (WPOI) and tumor infiltrating lymphocytes (TILS) may have prognostic implications. We aim to report the incidence of these factors and its association with clinical outcome post-operative OCSCC patients treated at our institute. <h3>Materials/Methods</h3> 150 post-operative patients of OCSCC undergoing curative oncological resection were analyzed with median follow up time 18 months from year 2019 to 2021. WPOI (WPOI-5) was defined as tumor dispersion of ≥1mm between tumor satellites. High risk WPOI was defined as (WPOI 4/5). Tumor budding is defined as the presence of single cancer cell or cluster of <5 cancer cells at the invasive front. DOI and staging were used as per AJCC 8^th edition. Disease free survival (DFS) and overall survival (OS) were estimated with Kaplan- Meier method. <h3>Results</h3> Median age was 50 years with M:F ratio of 135:15. Tumor site was buccal mucosa: tongue:alveolus:others as 84 (56%):49 (32%):13 (8.6%):4 (2.6%). LVI:PNI: close/positive margin: extra nodal extension was seen in 57 (38%):52 (34%):35 (23%):33 (22%) patients respectively. DOI=>10, DOI<10, high risk WPOI, tumor budding and TILS were observed in 79(52.6%), 71(47.3%), 102(72.8%), 97(71.3%) and 30(21.5%) patients respectively. Association of these have been listed in Table 1. AJCC eighth stage was I:II:III:IV as 30 (20%):32 (21.3%):38 (25.3%):50 (33.3%). Median RT Dose was 60 Gray. Sixty-four patients received CTRT (Median 5 cycles). Median Overall Treatment Time (OTT) was 98 (95-120) days. 2-year OS and DFS for the entire cohort was 81% and 67% respectively. 2-year DFS for patient with TILS was 86% vs.64% without TILS (p=0.07). PNI (60% vs. 72%; p=0.06) and bone invasion (47% vs 84%; p=0.04) portended poorer DFS. TB, WPOI and DOI did not statistically impact DFS in our cohort. <h3>Conclusion</h3> TB, WPOI and DOI are often associated in post-operative OCSCC with other adverse risk features. Patients with TILS tend to have a better clinical outcome