Moving beyond the stage: how characteristics at diagnosis dictate treatment and treatment-related quality of life year losses for women with early stage invasive breast cancer.

Background: Although evaluations of breast cancer screening programs frequently estimate quality-adjusted life-year (QALY) losses by stage, other breast cancer characteristics influence treatment and vary by mode of detection - i.e. whether the cancer is detected through a screening program (screen-detected), in between screening rounds (interval-detected) or outside the screening program (community-detected). Here, we estimate the association between early-stage invasive breast cancer (ESIBC) characteristics and treatment-related QALY losses. Methods: Using clinicopathological and treatment information from 675 women managed for ESIBC, we estimated the average five-year treatment-related QALY loss by detection group. We then used regression analysis to estimate the extent to which known cancer characteristics and the mode of detection, are associated with treatment and treatment-related QALY losses. Results: Community-detected cancers had the largest average QALY loss (0.76 QALYs [95%CI 0.73;0.80]), followed by interval-detected cancers (0.75 QALYs [95%CI 0.68;0.82]) and screen-detected cancers (0.69 QALYs [95%CI 0.67;0.71]). Adverse prognostic factors more common in community-detected and interval-detected breast cancers (large tumour sizes, lymph node involvement, high grade) were largely associated with QALY losses from mastectomies and chemotherapy. Receptor positive subtypes, more common in screen-detected cancers, were associated with QALY losses related to endocrine therapy. Conclusions: The associations between ESIBC characteristics and treatment-related QALY losses should be considered when evaluating breast cancer screening and treatment strategies.