Correlation of Ki-67 Proliferative Antigen Expression and Tumor Response to Induction Chemotherapy Containing Cell Cycle-Specific Agents in Head and Neck Squamous Cell Carcinoma

Determine if highly proliferative head and neck squamous cell carcinomas, assessed by pretreatment Ki-67 expression, respond more robustly to induction chemotherapy (IC) that is selectively toxic to cycling cells. Retrospective analysis of 59 patients treated with IC and chemoradiation. IC included either nab-paclitaxel, cisplatin, 5-FU and cetuximab (APF-C, n = 27) or docetaxel, cisplatin, 5-FU +/− cetuximab (TPF+/−C, n = 32). Ki-67 expression was assessed by immunohistochemistry. Tumor response (complete/partial/stable/progressive) at the primary site after two IC cycles was evaluated by visual examination in all patients. In the APF-C sub-group, tumor response (primary site and neck nodes) after two IC cycles was evaluated by computed tomography (CT) and fluorodeoxyglucose-positron emission tomography (FDG-PET)/CT. Ki-67 expression (median 66%, range: 16–97) did not differ across the tumor response categories assessed by visual examination (p = 0.95), CT (p = 0.30), or FDG-PET/CT (p = 0.65). Median decrease in summed SUV_max of measured lesions was 71.6% (range: 8.3–100%). The Pearson correlation coefficient between Ki-67 expression and the percent decrease in summed SUV_max was 0.48 (p = 0.02). Ki-67 expression was not different between those with or without a relapse (median: 60 and 71%, p = 0.10). In multivariate regression analysis (MVA) controlling for p16 positive oropharyngeal SCC status and smoking status, Ki-67 expression was not significantly associated with tumor response by visual examination (coefficient estimate −0.002, standard error 0.010, p = 0.84), CT (coefficient estimate −0.007, standard error 0.011, p = 0.54), FDG-PET/CT (coefficient estimate 0.006, standard error 0.008, p = 0.51), the percent decrease in summed SUV_max (coefficient estimate 0.389, standard error 0.222, p = 0.09), or relapse events (OR = 1.02(95%CI:0.99–1.05), p = 0.28). No significant relationships were found in MVA between pretreatment Ki-67 expression and tumor response to IC or to relapse.