Survival (OS) and progression-free survival (PFS) results after induction chemotherapy (IC) followed by de-escalated chemoradiotherapy (RDCRT) for locally advanced (LA) HPV positive oropharynx cancer (HPVOPC.

Abstract

6058 Background: HPVOPC has a significantly better prognosis and survival than HPV negative cancer resulting in overtreatment with significant acute and late toxicities and mortality. Radiation therapy is the single greatest determinant of toxicity. Studies to support reduction of radiation dose are a high priority. IC improves local regional control, reduces distant metastases, and may support radiotherapy de-escalation. Patients with T4, ECE, and N2c disease have poorer local regional control (LRC) and a higher rate of distant metastases (DM) and may be suitable for this option. Methods: Data was combined for the experimental arm of a previously reported Phase 3 trial (12 subjects, NCT01706939) and a continuation Phase 2 trial (20 subjects, NCT02945631). After informed consent subjects who were PCR+ HPVOPC, smoked < 20 py, and were LA or functionally unresectable were treated with Taxotere, cisplatin and reduced 5-fluorouracil (mTPF) for 3 cycles and then assessed for response. Responders were treated with 5600 cGy and weekly carboplatin, and then followed for LRC, DM, PFS, OAS and toxicity. Data was analyzed as of 2/1/21. 85% LRC at 3 years was considered non inferior to standard of care chemoradiotherapy. An acceptable end point was predetermined to be 80% PFS and 85% LRC at 3 years in this LA population. Results: 32 subjects were entered and included in the analysis, all responded to IC and had RDCRT. 2 patients with non-HPV16 subtypes were initially entered, treated with IC, responded, and then were taken off study and excluded from the analysis due to non-HPV 16 subtype. They were treated with 7000 cGy and are alive and well. Poor risk factors (ECE, T4, N2c, Non-HPV16 subtype) were present in 72% of 32 subjects; 22 (69%) never smoked. At data cutoff with a median follow up of 50m (21-95m), 28/32 (87.5%) have LRC, 1/32 DM (3.1%), OS is 28/32 (87.5%) and PFS is 27/32 (84.4%). All 5 patients who recurred did so in the first 12m (median 8m); all had 1 or more poor risk factors and 1 is alive with disease 42m post recurrence. 2 year LRC, PFS and OS are 87.4% [95% CI: 69.8%, 95.1%], 84.4% [95% CI: 66.5%, 93.2%] and 90.6% [95% CI: 73.7%, 96.9%] respectively. There was no therapy-related mortality, generally rapid recovery from CRT and minimal long term consequences (to be reported). Conclusions: Induction with mTPF followed by RDCRT resulted in excellent LRC, PFS and OS in patients with LA HPV OPC and significant risk factors. These results compare favorably to standard of care and other dose de-escalation trials in high and low risk categories. This treatment paradigm is highly effective in a LA, high risk HPVOPC patients and is a reasonable treatment option to be compared to other de-escalation treatment plans in Phase 3 trials for this higher risk population. Clinical trial information: NCT02945631, NCT01706939.