Margin status and survival outcomes after breast cancer conservation surgery: prospectively registered systematic review and meta-analysis

Journal article

Background and purpose: In early-stage breast cancer, a tumour-bed boost (TBB) reduces the risk of local recurrence (LR) by around 50 % but increases the risk of breast induration. LR incidences of 3 % at 5 years and 6 % at 10 years have been proposed as thresholds where benefits outweigh the potentially detrimental effects of a TBB. Therefore, this post-hoc analysis of the Danish Breast Cancer Group (DBCG) IMN2 study aimed to investigate LR rates according to prognostic risk factors to identify indications for a TBB. Material and methods: From the DBCG IMN2 study, 2,430 node-positive patients operated with breast-conserving surgery were included for analysis. They received irradiation to the residual breast and regional nodes with or without internal mammary node irradiation according to laterality. Radiotherapy was 3D-conformal. TBB was delivered sequentially as 10 Gy/5 Fx (41–49 years) and 16 Gy/8 Fx (≤ 40 years or margin < 2 mm). Patients with and without a TBB were analysed separately. Prespecified subgroups included known prognostic risk factors. Results: Median follow-up was 13.7 years, and the cumulative incidence of LR was 1.7 % (95 % CI, 1.2–2.2) at 5 years and 3.6 % (95 % CI, 2.9–4.3) at 10 years. In patients ≥ 50 years, 1,872 patients were treated without a TBB. Among these, 145 patients with an ER-/HER2- tumour had a 10-year cumulative incidence of LR of 8.3 % (95 % CI, 4.5–13.5). No other subgroups exceeded 6 % at 10 years. Conclusion: Our results suggest that node-positive patients 50 years or older with an ER-/HER2- tumour may obtain a clinically relevant benefit from a TBB.

Authors: Bundred, JR; Michael, S; Stuart, B; Cutress, RI; Beckmann, K

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: BMJ
• Journal: The BMJ
• Volume: 378
• Pages: e070346-e070346
• Publication date: 2022-09-21
• Acceptance date: 2022-07-28
• DOI: 10.1136/bmj-2022-070346
• ISSN: 1756-1833
• Language: English
• Keywords: Hazard ratio; Mastectomy; Meta-analysis; Breast-conserving surgery; Oncology; Neoadjuvant therapy; Surgery; Ductal carcinoma; Surgical margin; Breast cancer; Margin (machine learning); Medicine; Breast surgery; Internal medicine; Confidence interval; Cancer