Receipt of adjuvant systemic therapy among patients with high-risk breast cancer detected by mammography screening

Background: Few studies have compared screen-detected (SD) breast cancer patients with symptomatic patients for the frequency and determinants of receipt of adjuvant systemic therapy according to accepted guidelines. Methods: Depending on the date of diagnosis, adjuvant therapy guidelines from the 5th, 6th, and 7th St. Gallen International Conferences were used as standards to audit the treatment of 598 node-negative high-risk patients (59% SD) and 430 node-positive patients (40% SD) aged 50-69 years from an Italian cancer registry (1997-2001). Odds ratios (OR) and 95% confidence intervals (CI) were calculated using backward stepwise logistic regression models. Results: Among node-negative high-risk patients, SD cancers were smaller (P = 0.000) and of lower grade (P = 0.003). Downgrading was generally from grade 3 to grade 2, with an increased proportion of patients placed in the high-risk category due to grade 2 alone. The total rates of adjuvant systemic therapy were similar (58 vs. 60%) whereas SD patients were less often treated according to the guidelines (34 vs. 45%; OR = 0.61; 95% CI, 0.44-0.86). After adjustment for tumour size and other weaker confounders, the OR was 0.99 (95% CI, 0.67-1.46). Among node-positive patients, the OR of receiving the standard adjuvant systemic therapy did not differ between SD and symptomatic cancers. Conclusions: SD cancers amplified the prognostic heterogeneity of node-negative high-risk patients. Their lower likelihood of being treated according to the guidelines was largely explained by their lower risk profile. No evidence was found to suggest that physicians held a priori assumptions about the relative biological indolence of SD cancers.