Natural course of distant metastases following radiotherapy or chemoradiotherapy in HPV-related oropharyngeal cancer

Abstract

To describe the natural course of distant metastases (DMs) following radiotherapy (RT) or chemoradiotherapy (CRT) in HPV(+) oropharyngeal carcinoma (OPC). OPC treated with RT/CRT from 1/1/2000 to 5/31/2010 were reviewed. The natural course of DM were compared between HPV(+) and HPV(-) cohorts. Median follow-up was 3.9 years. The DM rate were similar (11% vs. 15% at 3-years, p=0.25) between the HPV(+) (n=457) vs. the HPV(-) (n=167) cases. While almost all (24/25) HPV(-) DM occurred within 2-years following RT (1 was at 2.1 years), 7/54 (13%) of HPV(+) DM were detected beyond 3 years (up to 5.3 years). Disseminating to >2 organs occurred in 18 (33%) HPV(+) vs. none in HPV(-). Post-DM survival rates were 11% vs. 4% at 2-years (p=0.02) for the HPV(+) vs. HPV(-) cases respectively. 5/6 HPV(+) with lung oligo-metastasis were still alive with stable disease beyond 2-years after salvage procedures for DM (chemotherapy: 3; surgical resection: 2; radiotherapy: 1). Although DM rates are similar, the natural course of HPV(+) DM differs from that of HPV(-) patients: it may occur after a longer interval, often with a "disseminating" phenotype, and a small number may have prolonged survival after salvage for DM.