Background: In ON, testing for HER2 overexpression in ESBC was approved, along with trastuzumab (T) treatment with chemotherapy for HER2 positive (IHC = 3 or FISH ≥2.0) tumors in 2005. Guidelines for testing and treatment must be met for provincial T reimbursement. To study adherence to HER2 testing and T utilization guidelines in ESBC, we first describe patient access to HER2 testing by age, tumor, stage, urbanicity and income. Methods: A population-based retrospective cohort of ESBC patients diagnosed in 2006 and 2007 was identified using the Ontario Cancer Registry and for whom ≥1 pathology report was available from Cancer Care Ontario (CCO). All BC-related pathology reports were individually reviewed to identify early stage, resected, primary BC. Information was collected on surgical procedure, TN stage, histologic grade, receptor status (ER/PR) and HER2 test provision. Linkage to other administrative databases provided income quintile, urban vs. rural residence and institution of diagnosis. Odds ratios were calculated to determine association of HER2 testing with any pathologic or socioeconomic factors. Results: The 2-year cohort contains 13,430 ESBC patients, 60% of which had breast conserving surgery. 29,746 (2.2/patient) pathology reports were reviewed. 13% of the cohort had rural residences, and 95% were alive at end of follow-up. Age at diagnosis was distributed as: 5% < 40 years, 18% 40-49 years, 25% 50-59 years, 24% 60- 69 years, 18% 70-79 years and 10% ≥80 years. Stage at diagnosis was: 35% stage I, 32% stage II, 10% stage III and 22% stage unknown after removing all stage IV. No differences in HER2 testing were observed for patients across income quintiles (P>0.3550). Patients ≥80 years (P<0.0001) and <40 years (p=0.0074) had significantly lower odds of receiving ≥1 HER2 test than patients 40-49 years. ESBC of higher histologic grade had significantly greater odds (P<0.0001) of ≥1 HER2 test compared to grade I ESBC. Patients from rural areas had lower odds of HER2 testing compared to urban patients (P<0.0001). Conclusions: For the 2 years 2006-2007: 13,430 ESBC patients were identified from the OCR for which ≥1 pathology report was available from CCO. Age, stage at diagnosis, and surgical procedure were representative of an ESBC population. HER2 testing was universally available per Ontario policy, but not all reports were submitted to CCO. The odds of having a documented HER2 test were not affected by income, but testing was more likely to be documented for high grade tumours and less likely to be documented for the youngest and oldest women and those with rural residence. Pathology reports missing from CCO are being sought. Adherence to guidelines for testing, treatment with T and cardiac monitoring during treatment will be assessed.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P1-10-09.