Updated Report on the Utility of Worst Pattern of Invasion in Guiding Adjuvant Treatment in Early Stage Oral Cavity Cancer

Summary: Several pathological risk factors impact the postoperative management of early-stage oral cavity squamous cell carcinoma (OSCC), with the worst pattern of invasion (WPOI), particularly WPOI-5, being a key prognostic marker. Although optional in pathology reports, WPOI could guide adjuvant therapy for early-stage OSCC. At ACRO 2024, we presented findings regarding the impact of adjuvant treatment on disease outcomes for patients with early-stage OSCC and WPOI-5, despite a limited sample size. Here, we provide an updated institutional report to assess if WPOI-5 warrants adjuvant radiation therapy in this patient population. This is a single- institution retrospective analysis of patients with early-stage OSCC (T1-2 Nx-N0 M0) and WPOI-5 who were either observed or treated with adjuvant radiation therapy. WPOI-5 was defined as tumor dispersion >/=1mm between tumor satellites. Tumor stage, per 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. We identified 10 patients meeting the inclusion criteria treated between December 2018 and February 2024 at our institution. Median follow-up time was 16.8 months. All patients underwent partial glossectomy, and 5 patients also underwent neck dissection at the time of initial surgery with the majority being unilateral neck dissection (4/5). All tumors had negative margins. 6 tumors demonstrated perineural invasion and none demonstrated lymphovascular invasion. Following surgery, 4 patients were observed and 6 underwent adjuvant radiation therapy (RT). RT dose was 60 Gy in 30 fractions. None of the patients received chemotherapy. At time of last follow up, 9 patients were alive and under active surveillance. Median progression free survival was 6.2 months in the observation cohort and not reached in the adjuvant RT cohort. 3 out of the 4 patients in the observation arm had recurred at time of analysis and all recurrences were locoregional. One of the patients in the observation cohort died due to disease progression. There have been no locoregional or distant recurrences in the adjuvant radiation cohort. 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-5 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. Patricia Pius (she/her/hers), MD (Presenting Author) - University of Oklahoma; Casey Buller, BS (Co-Author) - OU College of Medicine; Paul Pitts (he/him/his), BS MBA (Co-Author) - OU College of Medicine; Timothy Malouff (he/him/his), MD (Co-Author) - Mayo Clinic Radiation Oncology; Greg Krempl, MD (Co-Author) - OU College of Medicine; Christina Henson, MD (Co-Author) - University of Oklahoma