Second conservative treatment has emerged as an option for patients with second ipsilateral
breast tumour event after conserving surgery and breast irradiation. We aimed to address
the lack of evidence regarding second breast event treatment by comparing oncological
outcomes after conservative treatment or mastectomy.Oncological outcomes were analysed
using a propensity score-matched cohort analysis study on patients diagnosed with
a second breast event between 01/1995 and 06/2017. Patient data were collected from
15 hospitals/cancer centres (7 European countries). Patients were offered mastectomy
or lumpectomy plus brachytherapy. Propensity scores were calculated with logistic
regression and multiple imputations. Matching (1:1) was achieved using the nearest
neighbour method including 10 clinical/pathological data related to second breast
event. The primary endpoint was 5-year overall survival from the salvage surgery date.
Secondary endpoints were 5-year cumulative incidence of third breast event, regional
relapse and distant metastasis, and disease-free and specific survivals. Complications
and 5-year incidence of mastectomy were investigated in the conservative treatment
cohort.Among the 1327 analysed patients (mastectomy:945/conservative treatment:382),
754 were matched by propensity score (mastectomy:377/conservative treatment:377).
Median follow-up was 75.4 months (95%CI 65.4-83.3) and 73.8 months [95%CI 67.5-80.8)
for mastectomy and conservative treatment, respectively (p=0.9). In the matched analyses,
no differences in 5-year overall survival and cumulative incidence of 3rd breast event
were noted between mastectomy and conservative treatment (88% (95%CI 83.0-90.8) versus
87% (82.1-90.2); p=0.6 and 2.3% (95%CI 0.7-3.9) versus 2.8% (95%CI 0.8-4.7); p=0.4
respectively). Similarly, no differences were observed for all secondary endpoints.
Five-year cumulative incidence of mastectomy was 3.1% (95%CI 1.0-5.1).To our knowledge,
this is the largest matched analysis between mastectomy and conservative treatment
combining lumpectomy with brachytherapy for second breast event. Compared to mastectomy,
conservative treatment does not seem to be associated with any differences in terms
of oncological outcome. Consequently, conservative treatment could be considered a
viable option for salvage treatment.
