Tumor growth rate as a prognostic factor for metastatic or recurrent adenoid cystic carcinoma of the head and neck patients treated with carboplatin plus paclitaxel

Background: Large prospective studies of chemotherapy for metastatic or recurrent adenoid cystic carcinoma (ACC) of the head and neck are lacking due to the rarity of ACC. The aim of this study is to evaluate the efficacy of carboplatin plus paclitaxel toward ACC and perform an exploratory investigation of the prognostic factors to investigate the optimal strategy for metastatic or recurrent ACC.Methods: We retrospectively analyzed recurrent or metastatic ACC patients treated with carboplatin plus paclitaxel between April 2007 and September 2019 in our hospital. Objective response rate (ORR), disease control rate (DCR), progression-free survival (PFS) and overall survival (OS) were evaluated, and an exploratory analysis of the prognostic factors including tumor growth rate (TGR) was conducted.Results: A total of 26 ACC patients were enrolled. ORR and DCR were 11.5% and 76.9%; the median PFS and OS were 8.1 and 22.3 months, respectively. From the results of the multivariate analysis, higher (≥ 6%/month) TGR was associated with worse PFS (hazard ratio [HR] 7.00, 95%CI 1.34–36.53, p = 0.02) and OS (HR 29.33, 95%CI 3.38–254.80, p Conclusions: Carboplatin plus paclitaxel showed modest efficacy for recurrent or metastatic ACC patients. Watchful waiting may be optimal for ACC patients with lower TGR. Systemic chemotherapy should be considered when TGR increases during active surveillance.