Fat necrosis and parenchymal scarring after breast-conserving surgery and radiotherapy with an intraoperative electron or fractionated, percutaneous boost: a retrospective comparison.

BACKGROUND: The aim of this retrospective analysis was to evaluate mammographic changes such as fat necroses and parenchymal scarring in the breast tissue within the first 3 years after breast-conserving surgery (BCS) and whole-breast irradiation with an additional intraoperative electron boost (IO-B) versus fractionated percutaneous boost (FP-B).

METHODS: A total of 53 breast cancer patients (stage I/II) treated between 2006 and 2008 were included. All patients underwent BCS followed by fractionated whole-breast radiotherapy with a total dose and single dose of 50.4 and 1.8 Gy. Twenty patients had 10 Gy IO-B using electrons, and 33 patients were treated with a FP-B with 10.8 Gy. The IO-B was performed using the mobile linear accelerator NOVAC 7. The follow-up mammograms were focused on fat necroses, parenchymal scarring and skin thickening.

RESULTS: Fat necroses occurred significantly more frequently in IO-B patients compared to FP-B patients (50.0 vs. 18.2 %). The fat necroses were mammographically detected a median of 17 versus 23 months post-surgery for the IO-B versus FP-B patients. The median size of fat necroses was 24 (14-30) mm for the IO-B group and 14 (4-53) mm for the FP-B group. Parenchymal scarring in the grade 3-4 tumor bed area was seen significantly more frequently in the IO-B patients (55.0 vs. 21.2 %). Skin thickening did not differ significantly.

CONCLUSION: The IO-B led to significantly more fat necroses and local restricted parenchymal scarring in our analysis.