Efficacy of neoadjuvant immunochemotherapy followed by surgery in locally advanced buccal squamous cell carcinoma: A single-center real-world study.

6081 Background: The 5-year overall survival (OS) rate for locally advanced (stage III–IV) buccal squamous cell carcinoma (LA BSCC) is under 50%. In stage IV disease, the 2-year OS rate is under 45%, and the 5-year OS rate is under 30% (29.3% for the anterior buccal and only 18.7% for the posterior buccal). Evidence is limited regarding whether betel nut chewing and tumor subsites influence the efficacy of neoadjuvant immunochemotherapy. Methods: Retrospective analysis of 115 patients with LA BSCC received neoadjuvant therapy at Hunan Cancer Hospital between August 2021 and October 2024. Treatment regimen: Neoadjuvant albumin-bound paclitaxel plus cisplatin or carboplatin combined with a PD-1 inhibitor, followed by definitive surgery. Postoperative adjuvant radiotherapy or chemoradiotherapy was administered based on pathological findings. Primary endpoint: Pathological complete response and major pathological response (pCR/MPR) rate; Secondary endpoints: Overall survival (OS) and disease free survival (DFS) at 1 and 2 years; Subgroup analyses: Outcomes were evaluated by betel nut chewing history, tumor subsite, and TNM stage. Results: Of 113 evaluable patients, 16% had stage III and 84% had stage IV disease. A history of betel nut chewing was present in 71.9%. The objective response rate to neoadjuvant therapy was 83.5%, including a 28.3% clinical complete response rate. 98 patients proceeded to surgery; the pCR/MPR rate was 27.6%, and the partial pathological response (pPR) rate was 52.0%. With a median follow-up of 29 months (15-53 months), 1-year OS and DFS rates were 80.5% and 74.3%, respectively; 2-year OS and DFS rates were 70.0% and 67.5%, respectively. 2-year OS did not differ significantly by betel nut chewing ( P =0.8578) or by tumor subsite (anterior vs posterior buccal; P =0.5568). More advanced TNM stage was associated with poorer survival ( P =0.0352). Patients achieving pCR or MPR had significantly better 2-year OS and DFS than those who did not ( P =0.0386 and P =0.0102, respectively). Grade≥3 adverse events occurred in 18% of patients and no treatment-related deaths were observed. Conclusions: Neoadjuvant immunochemotherapy increased the 2-year OS rate of LA BSCC to 70%, with the 27.6% pCR/MPR rate. Treatment efficacy did not differ by betel nut chewing or by tumor subsite, whereas TNM stage remained an independent prognostic factor. Deep pathological response (pCR/MPR) was associated with superior long-term outcomes. Number 2-yr OS rate(%) p value 2-yr DFS rate(%) p value Tumor stage III 18/113 88.89 0.1558 78.75 0.0352 IVa 64/113 71.12 66.54 IVb 31/113 54.17 39.13 Tumor subsite Anterior buccal 88/113 69.85 0.5568 60.30 0.9963 Posterior buccal 25/113 64.29 60.00 Pathological response rate pCR+MPR 27/98 78.95 0.0386 78.95 0.0102 pPR 51/98 83.43 72.66