894P - Is pathological complete response (PCR) a surrogate endpoint of overall survival in patients with technically unresectable oral cavity cancers? A real-world data study of 900 plus patients

Background

Technically unresectable oral cavity squamous cell cancers (OCSCC) are non-amenable to upfront surgery. Neo-adjuvant chemotherapy (NACT) can downstage the tumor and facilitate surgical resection. Pathological complete response (PCR) post NACT is a surrogate endpoint of overall survival in rectal and breast cancers. However, it’s importance in patients with borderline resectable OCC is unknown.

Methods

This was an institutional review board approved retrospective analysis of a prospectively collected dataset of borderline resectable OCSCC patients who received NACT. Adult patients with an Eastern Co-operative Gncology Group (ECOG) performance status (PS) 0-2 who were deemed as technically unresectable in a multi-disciplinary clinic (MDC) were included. These patients received 2-3 cycles of NACT (3-weekly) and underwent a response assessment. Depending on response and general condition, they were re-assessed in MDC and further therapy was decided. Patients with good general condition who became resectable underwent surgery followed by appropriate adjuvant therapy. Overall survival (OS) was calculated from date of diagnosis to date of death. Kaplan-Meier method was used for estimation of OS. Impact of pathological response on OS was assessed using the log-rank method.

Results

929 patients underwent surgery followed by adjuvant CTRT in 26.7% patients or adjuvant RT in 1.3% patients. 76 (8.2%) patients attained pathological complete response. 871 (93.8%) achieved negative margins. Three hundred forty (39.3%) patients had pT4 disease. Lympho-vascular invasion was seen in 53 (5.7%) while peri-neural invasion was seen in 186 (20.0%) patients, and 338 (36.4%) had extra-nodal extension. The median OS of entire cohort was 17 months (95% CI: 14.7 – 19.3 months). The median OS of patients who attained PCR was 55 months (95% CI: 22.9 – 87.1 months) vs 16 months (95% CI: 13.9–18.1 months) for those who did not attain PCR (p=0.004). The corresponding 10-year OS were 21.1% (SE-3.2%) and 40.5% (SE-7.4%).

Conclusions

Pathological complete response is a surrogate marker of long-term overall survival in patients of technically unresectable oral cavity cancers.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

The authors.

Funding

Has not received any funding.

Disclosure

The author has declared no conflicts of interest.