Introduction: This study had three aims: to establish the incidence of ipsilateral breast tumour recurrence (IBTR) in a community treatment setting, to evaluate known factors--in particular younger age (< 40 years)--predictive for local recurrence, and to assess the impact of local recurrence on disease-specific survival (DSS).
Methods: A consecutive series of 1,540 women with node-negative breast cancer, diagnosed between the ages of 18-75 years, were prospectively accrued between September 1987 and September 1999. All had undergone a resection of the primary breast cancer with clear margins, an axillary lymph node dissection with a minimum of four sampled nodes, and breast-conserving surgery (of any type).
Results: During the study follow-up period, 98 (6.4%) IBTRs and 117 (7.6%) deaths from or with breast cancer were observed. The median time to IBTR was 3.1 years and to death from or with disease was 4.3 years. In the multivariate Cox proportional hazards (PH) regression model for IBTR with adjuvant therapy factors, independent risk factors included age < 40 years (relative risk (RR) = 1.89, 95% confidence interval (CI) of 1.00 - 3.58), presence of intraductal disease (RR = 1.81, 95% CI = 1.15-2.85) and histological grade ('G2' or G3 versus G1: RR = 1.59, 95% CI = 0.87-2.94). In the multivariate Cox PH regression model for DSS with adjuvant therapy factors, independent risk factors included previous IBTR (RR = 2.58, 95% CI = 1.41-4.72), tumor size (1-2 cm versus < 1 cm: RR = 1.95, 95% CI = 1.05-3.64, > 2 cm versus < 1 cm: RR = 2.94, 95% CI = 1.56-5.56), progesterone receptor status (negative or equivocal versus positive or unknown: RR = 2.15, 95% CI = 1.36-3.39), lymphatic invasion (RR = 1.78, 95% CI = 1.17-2.72), and histological grade ('G2' or G3 versus G1: RR = 8.59, 95% CI = 2.09-35.36). The effects of competing risks could be ignored.
Conclusion: The Cox PH analyses confirmed the importance of known risk factors for IBTR and DSS in a community treatment setting. This study also revealed that the early occurrence of an IBTR is associated with a relatively poor five-year survival rate.