10-Year oncological outcome report after second conservative treatment for ipsilateral breast tumor event.

Purpose: To analyze long-term oncological outcome after 2nd conservative treatment (2CT) for patients with ipsilateral 2nd ipsilateral breast tumor event (2IBTE).

Materials/methods: In this retrospective observational study (N°F20210402152843), patients with 2IBTE underwent 2CT (lumpectomy + tumor bed re-irradiation). 3IBTE (3IBTE-FS), regional relapse- (RRFS) and metastatic disease- (MD-FS) free survivals as well as disease-free (DFS), specific (SS) and overall (OS) survival were analyzed. Late toxicity was reported.

Results: Between 09/2000 and 04/2022, 244 patients presented a 2IBTE and underwent a 2CT. Among them, 113 pts with a minimum follow-up of 60 months were analyzed. Median time interval between 1st and 2IBTE was 13.5 years [2-35]. Median 2IBTE age was 66.2 years [31-85]. 2IBTE were adenocarcinomas (77 %). Tumor size was < 20 mm (86.7 %). 2IBTE were grade 1/2 (75 %), with positive hormonal receptor (85 %) and clear surgical margins (no ink on tumor, 90.3 %). In the APBI classification, 21 pts were high-risk (18.6 %), while 77 % were Luminal A/BHer2-. With a MFU of 121.5 months [CI95% 111.7-129.6], 10-year 3IBTE-FS was 89 % [83-96]. Then-year RRFS, MDFS, DFS, SS and OS were 94 % [89-100], 89 % [83-96], 78 % [70-87], 95 % [91-100] and 94 % [90 -99] respectively. In multivariate analysis, APBI classification (high-risk; HR2.66 [1.01-7.1], p = 0.049) and tumor size (≥20 mm; HR2.64 [1.02-6.8], p = 0.045) were considered independent prognostic factors for DFS.Ninety-seven late complications were observed (fibrosis 64 %) with 6.2 % G ≥ 3 late toxicity. Cosmetic outcome was excellent/good in 91.2 %.

Conclusions: With long follow-up, 2IBTE managed with 2CT allows second breast preservation without oncological outcome compromise and acceptable G ≥ 3 toxicity.