Background: Salivary squamous cell carcinomas (SCC) represent a unique disease entity, as many are thought to represent metastases from primary cutaneous malignancies. Nevertheless, they represent a significant proportion of parotid gland cancers and have a notably poor prognosis. Recently, there has been much debate in the literature as to the utility of adjuvant chemotherapy in the treatment of these malignancies, with most studies concluding that there is no survival benefit. We aim to investigate the outcomes associated with the use of adjuvant radiotherapy and chemoradiotherapy in the treatment of early- and late-stage salivary SCC.
Methods: A retrospective study of 2285 adult salivary SCC diagnosed from 2004-2014 in the NCDB was conducted. Patients were divided into early- (I/II) and late-stage (III/IV) groups. Demographic, facility, tumor, and survival variables were included in the analyses. Multivariate Cox survival regressions as well as univariate Kaplan-Meier analyses were conducted.
Results: The use of adjuvant chemoradiotherapy for late-stage patients was associated with improved survival compared to the use of adjuvant radiotherapy alone (HR 0.774, p=0.026). 5-year survival for late-stage patients treated with surgery alone, surgery with adjuvant radiotherapy, and surgery with adjuvant chemoradiotherapy was 31.1% (SE: 2.5), 45.6% (SE: 2.2), and 58.9% (SE: 3.4) (A). Use of adjuvant therapy (either chemoradiotherapy or radiotherapy alone) was associated with improved survival for early-stage patients (HR 0.746, p=0.037) (B).
Conclusion: The addition of chemotherapy to the adjuvant therapy of late-stage patients with salivary SCC may result in improved long-term survival. Expanded use of adjuvant therapy for early-stage disease may also improve patient outcomes.