Utility of Worst Pattern of Invasion in Guiding Adjuvant Treatment in Early- Stage Oral Cavity Cancer

Purpose: There are several pathologic risk factors that influence post-operative management of early-stage oral cavity squamous carcinoma (OSCC). The worst pattern of invasion (WPOI), ranging from I-V, is a known prognosticator for OSCC, specifically WPOI-V. Because it remains optional in pathology reporting, it is not widely utilized to guide adjuvant therapy of early-stage OSCC. Our study aims to analyze clinical outcomes for early-stage OSCC with WPOI-V to determine whether WPOI-V is an indication for adjuvant radiation therapy in this population.

Methodology: This is a single-institution retrospective analysis of patients with early-stage OSCC (T1-2 Nx-N0 M0) and WPOI-V who were either observed or treated with adjuvant radiation therapy. WPOI-V was defined as tumor dispersion >/=1mm between tumor satellites. Tumor stage, as defined by the AJCC 8th edition, and histopathological features were collected from pathology reports at the time of initial surgery. Electronic medical records were used to collect information regarding patient demographics, adjuvant treatment and disease status. Median follow-up was defined as time from initial surgery to most recent follow-up. Median progression free survival (PFS) was defined as time from initial surgery to time of disease progression.

Results: We identified 4 patients meeting the inclusion criteria treated between December 2018 and December 2021 at our institution. Median follow up time was 36.7 months. All patients underwent partial glossectomy, and 3 patients also underwent selective unilateral neck dissection at the time of initial surgery. One patient underwent revision surgery due to positive margins on initial pathology, and subsequently had negative margins. All 4 tumors were well to moderately differentiated, with negative margins and absence of extra-nodal extension. 2 tumors demonstrated perineural invasion and none demonstrated lymphovascular invasion. Following surgery, 2 patients were observed and 2 underwent adjuvant radiation therapy to a dose of 60 Gy in 30 fractions. None of the patients received chemotherapy. At time of last follow up, all patients were alive and under active surveillance. Median PFS for the observation cohort was 32.8 months. Both patients in the observation arm had recurred at time of analysis and all recurrences were locoregional. There have been no locoregional or distant recurrences in the adjuvant radiation cohort.

Conclusions: While our study is limited by small sample size, it demonstrates the impact of high risk WPOI on tumor behavior and disease outcomes. Additionally, the presence of WPOI-V in early-stage OSCC might be more relevant than historic poor prognostic factors, and this patient population may benefit from adjuvant radiation. A larger, multi-institutional retrospective analysis is required to further investigate this trend.

References: Mishra A, Das A, Dhal I, et al. Worst pattern of invasion in oral squamous cell carcinoma is an independent prognostic factor. J Oral Biol Craniofac Res. 2022;12(6):771-776