377P - Oropharyngeal squamous cell carcinomas in Indian population: P16 positivity and treatment outcomes following chemoradiotherapy

Background

Human papillomavirus (HPV) associated oropharyngeal squamous cell cancers (OPSCC) are known to have better treatment response and outcome compared with HPV -negative ones. Testing for p16 expression is used as a surrogate for HPV testing. While p16- positive tumours comprise of majority of OPSCC in Western population, p16 -positive tumours in Asian population have remained low.

Methods

Data of Indian patients treated at a single institute between 2016 -2023 was ambispectively analyzed for rate of p16 positivity and clinical outcomes. Staining of ≥70% was considered positive for p16. Data entry and analysis was done using IBM SPSS Statistics v21.0.

Results

Between February 2016 – June 2023, 114 patients were treated, of which 106 had SCC. Majority subsites were tonsil (50, 47.2%), base of tongue (30, 28.3%), and soft palate (15, 14.2%). Testing for p16 was done in 66 patients (62%), of which 19 were p16-positive. Smoking history was noted in 36 patients (34%). Treatment modalities were CTRT for 74 patients (69.8%) and RT alone for 32 (30.2%). IMRT was utilized for majority patients (97, 91.5%). Chemotherapeutic agents were cisplatin for 61 (82.4%, 6 (9.8%) shifted to carboplatin) [3 weekly-9, weekly-52], carboplatin 11 (15%) and cetuximab 2 (3%). Treatment was completed by 101 patients (95.3%) [2 discontinued treatment, 3 died before treatment completion due to non-oncologic causes]. At 3 months, response assessment was done for 94 patients, of which 74 (78.7%) had complete response [14/15 (93.3%) p16-positive, 31/41 (75.6%) p16-negative]; 7 patients (7.4%) had incomplete response while 13 (13.8%) progressed. At median follow-up of 23 months (IQR 11–42); 90 patients were alive, 72 (71.3%) had disease under control. Relapse was seen in 9 patients (p16-positive – 0, p16-negative – 4, untested – 5). Median progression free survival was 17 months (IQR 5-37 months).

Conclusions

While p16 positivity amongst Indian OPSCC patients remains lower than Western counterparts, p16 -positive OPSCC have shown favorable response rates in Indian patients. Association of p16 positivity with improved response rates and fewer relapses in the Indian population warrants investigation in a larger randomized trial.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

Amrita Cancer Institute.

Funding

Has not received any funding.

Disclosure

All authors have declared no conflicts of interest.