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Abstract

Objectives: Neo-adjuvant (NACT) is being increasingly used in the management of locally advanced oral cavity cancers. The purpose of the study was to characterize histological tumor response to NACT of locally advanced borderline resectable buccal mucosa squamous cell carcinoma (BM-SCC) and determinewhether tumor response grading (TRG) predicts clinical outcome. Methods: TRG was evaluated on 66 surgical resection specimens obtained from buccal mucosa carcinoma patients who received NACT. Tumor response to NACT was determined using a system encompassing five tumor regression grades based on the estimation of the percentage of residual viable tumor in relation to the macroscopically identifiable previous tumor bed (TRG1 i.e. no residual tumour; TRG2: 1-5%; TRG3: 6-50%; TRG4: 51-95%; and TRG5: >96% residual tumor). The significance of this system was validated by correlation of the tumor regression grades with the corresponding clinicopathological characteristics and patient survival. Results: Five patients (TRG1: 7%) demonstrated a complete tumor regression after NACT, but in 61(93%) of the specimens a partial tumor regression was observed (TRG2: 15%; TRG3: 15%; TRG4: 57%; and TRG5: 5%).Tumor regression was significantly associated with tumor grade (p<0.001), skin involvement (p=0.017), and pT stage (p<0.001). Survival analysis showed a significant prognostic relevance of the applied regression system in multivariate analyses as a single independent prognostic factor for 5 year disease free survival (p=0.028; 95% confidence interval 0.014-0.997) and 5 year overall survival (p=0.041; 95% confidence interval 0.035-1.141). Conclusion: The effect of NACT in BM-SCC can be assessed by the determination of histological tumor regression, providing valuable prognostic information.

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