Background: The impact of early detection of second breast cancers in women who have survived a primary breast cancer is unknown. We examined the prognostic effect of detection of ipsilateral breast relapse (IBR) or contralateral breast cancer (CBC) in the asymptomatic relative to symptomatic phase.
Patients and methods: Subjects were women with histology-verified second (invasive or in situ) breast cancer (N = 1044) in a breast centre in Florence (1980-2005). Symptom status, test, tumour stage, and outcomes data were obtained from clinical records and linkage with mortality registry. Disease-specific survival was measured from first cancer diagnosis to avoid lead-time bias. Sensitivity analysis was used to allow for length-time bias.
Results: Second cancers (IBR = 455; CBC = 589; median age 60 years) were diagnosed in 699 asymptomatic and 345 symptomatic women (67% versus 3%, P < 0.0001). Mammography was more sensitive than clinical examination (86% versus 57%, P < 0.0001); however, 13.8% of cases were only identified clinically. Asymptomatic cancers were smaller than symptomatic for both IBR (P < 0.001) and CBC (P < 0.001). Early-stage tumours were more frequent in asymptomatic (58.1%) than symptomatic (22.6%) women (P < 0.0001). Fewer women with asymptomatic than symptomatic CBC had node metastases (P = 0.0001). Hazard ratio (HR) for asymptomatic (relative to symptomatic) detection was 0.51 (0.32-0.80) for IBR, 0.53 (0.36-0.78) for CBC, and 0.53 (0.40-0.72) in all subjects (P < 0.0001). Length bias-adjusted HRs ranged from 0.53 to 0.73.
Conclusion: Detection of second breast cancers in the asymptomatic phase leads to detection of early-stage cancer and improves relative survival by between 27% and 47%.