3500 - Prognostic Significance of Pathologic Complete Response after Neoadjuvant TPF Chemotherapy in Stage IV Oral Cavity Squamous Cell Carcinoma

Purpose/Objective(s): Induction chemotherapy in oral cavity squamous cell carcinoma (OSCC) remains controversial because survival benefit has not been consistently demonstrated. We hypothesized that treatment response, specifically pathologic complete response (pCR), identifies a prognostic subgroup and may function as a response-adapted selection marker. We evaluated oncologic outcomes of neoadjuvant docetaxel–cisplatin–5-fluorouracil (TPF) followed by surgery compared with upfront surgery in stage IVA–IVB OSCC, with primary endpoints overall survival (OS) and disease-free survival (DFS).

Materials/Methods: We performed a retrospective cohort study of consecutive patients with stage IVA–IVB OSCC treated with curative intent between 2014 and 2019 at one institution. Patients underwent neoadjuvant TPF followed by surgery (ICT+OP) or upfront surgery (OP). Secondary endpoints included pCR, tumor and nodal down-staging, and extranodal extension (ENE). Survival was estimated using Kaplan–Meier analysis and compared by log-rank test. Multivariable Cox proportional hazards models adjusted for age, clinical stage, margin status, ENE, and adjuvant therapy.

Results: A total of 146 patients were included (74 ICT+OP, 72 OP) with median follow-up 34.5 months. Neoadjuvant TPF significantly increased primary tumor down-staging (pT1–T2: 31% vs 1%, P<.001) but not nodal down-staging. pCR occurred in 10% of ICT+OP patients. Three-year OS was 55% vs 57% (P=.78) and DFS 46% vs 49% (P=.49) for ICT+OP vs OP. Within the ICT+OP cohort, pCR was associated with improved outcomes (3-year OS 100% vs 53%; DFS 86% vs 44%). ENE in residual disease predicted worse DFS (24% vs 55%, P=.03). On multivariable analysis, pCR independently predicted OS (HR 0.33, P=.04).

Conclusion: Neoadjuvant TPF did not improve survival at the cohort level but produced substantial tumor down-staging. Achieving pCR identified a favorable-prognosis subgroup and may serve as a response-adapted biomarker for treatment selection in advanced OSCC, whereas extranodal extension remained a strong adverse prognostic factor.