Disparities in receipt of guideline-concordant adjuvant chemotherapy and survival outcomes among immigrant patients with colon cancer: Real-world evidence from Ontario.

Abstract

1639 Background: Immigrants comprise a growing proportion of the Canadian population and may face unique barriers to accessing timely and guideline-concordant cancer care. While the “healthy immigrant effect” suggests that immigrants initially experience better health outcomes, it remains unclear whether this advantage extends to cancer treatment and survival. We studied whether disparities exist in the receipt of adjuvant chemotherapy and survival outcomes among recent immigrant patients with stage III colon cancer in Ontario compared with long-standing Ontario residents. Methods: A population-based real-world retrospective cohort study was conducted using linked administrative health databases housed at the ICES. Adults diagnosed with stage III colon cancer between 2007 and 2020 who underwent surgery within six months of diagnosis were included. Recent immigrants were defined as individuals with a landing date as a resident within ten years before diagnosis, identified using the Immigration, Refugees and Citizenship Canada database; long-standing residents had no recorded immigration date. The primary outcome was receipt of adjuvant chemotherapy within four months of surgery for their cancer. Secondary outcome was all-cause mortality. Results: The cohort included 16,724 patients, of whom 304 were recent immigrants (including 47 refugees). Compared to long-standing residents, recent immigrants were younger, had fewer comorbidities, and were more likely to reside in urban areas. In unadjusted analyses, recent immigrants were more likely to receive adjuvant chemotherapy (RR 1.37; 95% CI 1.23–1.53); however, this association was attenuated in the multivariate analysis (RR 1.08; 95% CI 0.99–1.19). Recent immigrants had significantly lower all-cause mortality, with an adjusted hazard ratio (HR) of 0.70 (95% CI 0.58–0.84). Conclusions: In this large population-based study, recent immigrants with stage III colon cancer in Ontario received comparable guideline-concordant adjuvant chemotherapy and had significantly better overall survival than long-standing residents. These findings suggest that, within a universal healthcare system, recent immigrants may not be disadvantaged in colon cancer treatment and perhaps have better outcomes once engaged in care. Further research is needed to assess whether these findings extend to other cancer types and to non-permanent resident populations.