Mode of detection and breast cancer mortality by follow-up time and tumor characteristics among screened women in Cancer Prevention Study-II

Purpose: In a screened population, breast cancer-specific mortality is lower for screen-detected versus symptom-detected breast cancers; however, it is unclear whether this association varies by follow-up time and/or tumor characteristics. To further understand the prognostic utility of mode of detection, we examined its association with breast cancer-specific mortality, overall and by follow-up time, estrogen receptor status, tumor size, and grade. Methods: In the Cancer Prevention Study-II Nutrition Cohort, 3975 routinely screened women were diagnosed with invasive breast cancer (1992–2015). Among 2686 screen-detected and 1289 symptom-detected breast cancers, 206 and 209 breast cancer deaths, respectively, occurred up to 24 years post diagnosis. Hazard ratios (HR) and 95% confidence intervals (CI) were calculated from Cox proportional hazard regression models. Results: Controlling for prognostic factors, symptom detection was associated with higher risk of breast cancer-specific death up to 5 years after diagnosis (HR_≤5years = 1.88, 95% CI 1.21–2.91) this association was attenuated in subsequent follow-up (HR_>5years = 1.26, 95% CI 0.98–1.63). Within tumor characteristic strata, there was a 1.3–2.7-fold higher risk of breast cancer death associated with symptom-detected cancers ≤ 5 years of follow-up, although associations were only significant for women with tumors < 2 cm (HR_≤5years = 2.42, 95% CI 1.19–4.93) and for women with grade 1 or 2 tumors (HR_≤5years = 2.72, 95% CI 1.33–5.57). In subsequent follow-up, associations were closer to the null. Conclusions: Screen detection is a powerful prognostic factor for short-term survival. Among women who survived at least 5 years after breast cancer diagnosis, other clinical factors may be more predictive of breast cancer survival.