Background: oncological principles of therapeutic mammaplasty (TM) is based on evidence arising from studies on the oncological safety of traditional breast conservation, i.e. wide local excision (WLE). Hence, oncological safety of TM is benchmarked to patients treated with WLE. However, TM can also be defined as a conversion of mastectomy (Ms) to breast conservation surgery applying plastic surgical techniques in patients conventionally requiring mastectomy. The aim of this study was to decide if TM was similar to WLE or Mx in terms of pathological characteristics.

Methods: 1006 consequtive patients were involved in the analysis, who were treated with TM, WLE or Ms in two Glasgow breast units between 2008 and 2011. Histopathological characteristics of patients treated with TM were compared to those treated with WLE or Ms. Statistical calculations were carried out with Chi-square test. The difference was considered statistically significant if p>0.05.

Results: 121 patients were treated with TM, while 600 patients were treated with WLE and 285 with Ms. Tumour size of TM was significantly different from WLE as well as Ms, although the difference between TM and WLE was more significant than between TM and Ms (TM/Ms/WLE: T1: 43.8%, 34%, 78%; T2: 52.1%, 54.7%, 21%; T3: 4.1%, 11.2%, 1%; TM vs. WLE: p<0.001; vs. Ms: p = 0.03). Tumour grade of TM was significantly higher than grade of WLE, but there was no significant difference between the grades of TM and Ms (TM/Ms/WLE: G1: 6.4%, 4.5%, 19.3%; G2: 37.6%, 41.8%, 54.8%; G3: 56%, 53.7%, 26%; TM vs. SZE: p<0.001; vs. Ms: p = 0.625). Similarly, significantly more axillary nodes were involved in patients treated with TM compared to patients with WLE, while the same was comparable in patients with TM and Ms (TM/Ms/WLE: 0: 73.5%, 70.4%, 87.7%; 1-3: 24.5%, 25.6%, 12.2%; >3: 2%, 4%, 0.2%; TM vs. WLE: p<0.001; vs. Ms: p = 0.601). In terms of histological subtypes, again, there was a significant difference between TM and WLE, but we found no difference when TM was compared to Ms (TM vs. WLE: p = 0.027; vs. Ms: p = 0.582). There was statistically significantly more ER and/or PR positive patients in the group treated with WLE compared to TM (ER/PR TM vs. WLE p = 0.012 / = 0.014), but ER/PR expression was similar in TM and Ms patients (ER/PR TM vs. Ms p = 0.890 / = 0.635). While the trend above was similar in HER-2 expression pattern, there was no statistically significant difference could be demonstrated in between the groups (table).

Discussion: pathological characteristics of patients treated with therapeutic mammaplasty is similar to patients treated with mastectomy, but significantly different from patients who were treated with WLE. Pathology after WLE is significantly more favourable compared to TM. Hence, studies investigating oncological safety of TM comparing to patients treated with WLE only may not be adequate, and Ms patients should be included in the analyses.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P5-15-07.