Background: Breast-conserving surgery is recommended in Norway and internationally in cases of early-stage breast cancer. We analysed the surgical methods used for breast-cancer patients by hospital providing treatment, age at the time of diagnosis, detection method and histopathological characteristics of the tumours in the period 2003 to 2018.
Material and method: Data on women of all ages diagnosed with invasive breast cancer (n = 47 004) were retrieved from the Cancer Registry of Norway's databases. We excluded women with distant metastases at the time of diagnosis (n = 1 773) and those for whom no surgical method was recorded (n = 2 638). The detection method was defined as breast cancer detected by screening, in inter-screening intervals, or outside BreastScreen Norway. The surgical methods chosen were compared by means of descriptive analyses.
Results: Slightly over half (23 661 of 42 593, i.e. 55.6 %) of the women in whom breast cancer was detected in the study period underwent breast-conserving surgery. The percentage increased from 1 189/2 423 (49.1 %) in 2003 to 2 070/2 958 (70.0 %) in 2018. There were large differences across hospitals. In the period 2015-2018 we found the highest proportion of breast-conserving surgery, 175/187 (93.6 %) for breast cancer detected by screening to be performed at Ålesund Hospital, and the lowest proportion, 121/351 (34.5 %) among women with breast cancer detected outside BreastScreen Norway, to be performed at Radiumhospitalet. Breast-conserving surgery was used most frequently on women with small tumours without spreading to axillary lymph nodes.
Interpretation: We found considerable differences in the surgical methods used across hospitals and for different detection methods.