Appropriate treatment for stage 1 and 2 Her2-positive and triple-negative breast cancer by immigration status in Ontario, Canada

Purpose — This study explored appropriate treatment received for stage 1 and 2 Her2-positive and triple-negative (TN) breast cancer (BC) among immigrants and long-term residents.

Methods — We identified women aged 18- 75 years diagnosed with BC in Ontario from 2012 to 2019. We stratified them into immigrants and long-term residents using the Immigration, Refugee, and Citizenship Canada Permanent Resident database (CIC). We linked to population-wide treatment databases to extract information on breast surgery, chemotherapy, and radiotherapy. We categorized them into 4 mutually exclusive groups based on subtype (Her-2 positive or TNBC) and breast surgery (breast-conserving surgery (BCS) vs. mastectomy). Appropriate treatment included chemotherapy for all (plus Herceptin if Her-2 overexpressing), plus breast radiation therapy if breast-conserving surgery was performed. We could not assess the receipt of endocrine therapy for the hormone receptor-positive subset of Her-2 overexpressors, or indications for postmastectomy radiation therapy. Odds ratios for receiving appropriate treatment were calculated using logistic regression, adjusting for age, resource utilization and area-level residential ethnicity concentration.

Results — Crude and univariate analyses showed no differences in the receipt of appropriate treatment. Similarly, adjusted analyses in each of the 4 subgroups showed no difference between immigrants and long-term residents. Among Her2-positive treated by(BCS) group,(Odds Ratio[OR] = 0.82, 95% Confidence Interval[CI] 0.65-1.03, and treated by mastectomy, OR = 0.95 (95% CI, 0.67-1.35). Among TNBC treated by BCS, OR = 0.81 (95% CI, 0.58-1.13), and treated by mastectomy,OR 0.85 (95% CI, 0.49-1.46).

Conclusion — Immigration status was not associated with the receipt of appropriate treatment amongst early-stage Her2-positive or TNBC breast cancer in Ontario.