Abstract
BACKGROUND: Breast conservation therapy (BCT) is well established for the management of primary operable breast cancer, with oncologic outcomes comparable to those of mastectomy. It remains unclear whether re-conservation therapy (RCT) is suitable for those patients who develop ipsilateral breast tumor recurrence (IBTR), for whom mastectomy is generally recommended. METHODS: We identified women who underwent BCT for invasive or ductal carcinoma in situ and developed IBTR as a first event, comparing the pattern of subsequent events and survival for those treated by RCT versus mastectomy. RESULTS: Of 16,968 patents who had BCT, 322 (1.9%) developed an isolated IBTR as a first event between 1999 and 2019. 130 (40%) had RCT and 192 (60%) mastectomy. Compared to mastectomy, the RCT patients were older (66 vs 53, < 0.001), had a longer disease-free interval (DFI: 5.8 vs 2.7 years (p < 0.001)), were less likely to have received RT (p < 0.001), endocrine therapy (ET) (p < 0.005) or combined RT/ET (< 0.001) as initial treatment, but the characteristics of their initial primary cancers and of their IBTR were comparable. At a median follow-up of 10.7 years following initial BCT and 6.5 years following IBTR, there were no differences in BCSS or OS between RCT and mastectomy. CONCLUSION: For BCT patients who developed IBTR as a first event, we observed comparable BCSS and OS from time of initial treatment and from time of IBTR, whether treated by RCT or mastectomy. These results support wider consideration of RCT in the management of IBTR, especially in the setting of older age and longer DFI.