Risk factors for local recurrence after conservative treatment in stage I breast cancer. Definition of a subgroup not requiring radiotherapy.

BACKGROUND Risk factors for local recurrence after breast-conserving treatment of early breast cancer have not previously been evaluated in settings where mammography has been a major pathway to diagnosis of both primary tumour and recurrences or in patients treated surgically by a formal sector resection. PATIENTS AND METHODS Three hundred eighty-one women with stage 1 primary breast cancer were randomised after a standardised sector resection to either a course of postoperative radiotherapy to 54 Gy to the breast (XRT group) or to surgery alone (non XRT group). At five years, 43 local recurrences, six of them in the XRT group, appeared. Patient characteristics collected from the medical records, histopathological characteristics determined by re-examination of slides, and mammographic characteristics from the pre-operative mammograms were evaluated as risk factors for recurrence by univariate and multivariate Cox proportional hazards models. Results are reported as relative hazards (RH) with 95% confidence intervals (95% CI). RESULTS In the univariate analysis comedo cancer, RH 3.5 (95%, CI 18 6.7), lobular cancers RH 2.8 (95% CI 1.1 7.1), mammographic appearance as circular/oval shaped density, RH 2.3 (95% CI 1.1 4.51, and mammographic appearance as a stellate lesion with microcalcifications inside the lesion, RH 3.8 (95% CI 1.1-13.0) were identified as risk factors for local recurrence. Age, with a RH of 0.97 (95% CI 0.94 0.99) for each increasing year was inversely associated with risk. A multivariate analysis, which also took postoperative radiotherapy into account, only showed comedo cancers with a RH 2.6 (95% CI 1.3-5.0) and mammographic appearance of a stellate lesion with microcalcification inside the lesion RH 4.5 (95% CI 1.1-17.6) to be statistically significant. The estimates for age RH 0.98 (95% CI 0.95 1.01 and lobular cancers RH 2.5 (95%, CI 0.98 6.6) were marginally changed, with widened CIs. Patients > 60 years of age, without comedo or lobular carcinomas were found to be at low risk 15.9% at five years in Kaplan Meyer estimate) of local recurrence, even without postoperative radiotherapy. CONCLUSION Low age, comedo and lobular cancers and mammographic appearance of the tumour as a stellate lesion with microcalcifications inside the lesion indicate an increased risk for local recurrence after sector resection in stage 1 tumours at five years. Patients > 60 years of age without comedo or lobular cancers are at low risk for local recurrence at five years even without postoperative radiotherapy.