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

Abstract

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. 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. 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. 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.