Outcome and treatment toxicity in east-indian versus white-canadian patients with oral cavity cancer following postoperative (chemo-)radiotherapy delivered under similar multidisciplinary care: A propensity-matched cohort study.

Purpose: We compare clinical behaviour of East-Indians and White-Canadians with oral cavity squamous cell carcinoma (OSCC) treated at a Western institution within a uniform health care system.

Materials/methods: Newly diagnosed OSCC patients who underwent postoperative (chemo-)radiotherapy (PORT/POCRT) between 2005 and 2017 were included. Data on ethnicity and other variables were extracted from patient-questionnaires, a prospective database and supplemented by chart review. Baseline characteristics were compared between East-Indian versus White-Canadian groups. A propensity-matched (1:1 ratio) of East-Indian versus White-Canadian cohorts was generated to compare locoregional control (LRC), distant control (DC), overall survival (OS), and acute and late toxicities.

Results: A total of 53 East-Indian and 467 White-Canadian OSCC patients were identified. Compared to White-Canadians, East-Indian patients were younger, had less exposure to smoking and alcohol (p < 0.001), but more chewed betel (areca) nut /tobacco (43% vs 0.2%, p < 0.001). Buccal/retromolar-trigone/lower gingiva primaries were more common in East-Indians (49% vs 25%, p < 0.001). Median follow-up was 5.0 years. Propensity-score paired analysis revealed inferior 3-year LRC (68% vs 81%, p = 0.030), non-significantly lower OS (61% vs 75%, p = 0.257), but similar DC (81% vs 87%, p = 0.428) in East-Indian versus White-Canadian patients. Actuarial rate of toxicities was higher in East-Indians vs White-Canadians: acute toxicity at 6 weeks: 47% vs 30%, p = 0.012; chronic trismus at 5-years: 16% vs 2%, p = 0.013.

Conclusion: East-Indian OSCC patients have a greater betel nut/ chewable tobacco exposure compared to White-Canadians and a different distribution of OSCC sites. Propensity-matched cohort analysis showed lower LRC and higher toxicities in East-Indian OSCC patients, suggesting a complicated interaction between genetic/biological and life-style factors.