Purpose: To study risk factors for local recurrence (LR) after breast-conserving therapy (BCT) for invasive breast cancer and, for patients with an LR, the mode of detection, location, treatment, influence of radiation therapy, and impact on survival.
Methods and materials: 1360 patients (median age 52 years; range 24-88) with a total of 1393 pT1-2 N0-1 tumors treated with BCT between 1980-1994 were studied (median follow-up 52 months). The adequacy of radiation treatment of the patients developing LR was studied in a quality control study. The impact of LR on overall survival and distant metastasis was studied in a Cox regression model with LR as a time-dependent covariate.
Results: A total of 88 LR occurred with a 5- and 10-year LR risk of 8 and 12%. Age was the only significant risk factor. Compared to patients > 65 years old, patients < 45 years old and patients 45-65 years old had a relative risk (RR) of 4.09 and 2.41, respectively, of developing LR. Risk on LR was found to increase gradually with younger age. Radiation therapy was considered adequate and did not play a role in influencing the LR rate. Almost 65% of the LR were true or marginal recurrences. Of all LR, 80% appeared during the first 5 years and were detected with equal frequency by the patient herself, the physician, and annual mammography. LR was a major predictor for distant metastasis (RR: 4.90; 3.15-7.62) and death (RR: 4.29; 2.93-6.28).
Conclusion: Young age is a major risk factor for LR and there is a significant gradual increase in LR with decreasing age. LR is associated with a higher risk of distant metastasis and death. Whether LR is the cause of or a marker for distant metastasis remains unresolved.