Quantitative assessment of breast volume changes after whole-breast irradiation for breast cancer using breast auto-segmentation

Breast Cancer Res Treat. 2024 Jan;203(2):205-214. doi: 10.1007/s10549-023-07146-0. Epub 2023 Oct 13.


Purpose: This study aimed to quantitatively estimate the changes in breast volume associated with radiotherapy in patients undergoing breast-conserving surgery and whole-breast irradiation (WBI).

Methods: Pre-WBI simulation computed tomography (CT) scans and post-WBI follow-up chest CT scans from a total of 1,151 breast cancer patients were analyzed using a deep-learning-driven auto-segmentation approach. The CT-based asymmetry index (CTAI) was calculated by dividing the volume of the irradiated breast by the volume of the contralateral breast. Significant breast shrinkage was defined as a CTAI < 0.85. To quantify changes in CTAI over the follow-up period, the CTAI ratio was determined as the post-WBI CTAI divided by the pre-WBI CTAI. A multivariate logistic regression analysis was conducted to identify potential variables associated with post-WBI significant breast shrinkage.

Results: The median CTAI values for pre- and post-WBI CT scans were 0.973 (interquartile range: 0.887-1.069) and 0.866 (interquartile range: 0.773-0.967), respectively. The difference between them was statistically significant (p < 0.001). Following WBI, there was an increase in the rate of significant breast shrinkage from 16.3 to 44.8%. The CTAI ratio showed a negative association with the time interval (p < 0.001, Pearson r = - 0.310). In the multivariate logistic regression analysis, lower pre-WBI CTAI, younger age, and longer interval between CT scans were found to be significantly associated with a higher occurrence of post-WBI significant breast shrinkage.

Conclusion: Breast volume decreases following WBI, and this decrease is correlated with an increased duration after WBI. These findings highlight the long-term consequences of WBI on breast asymmetry.

Keywords: Breast volume changes; Breast-conserving surgery; CT-based asymmetry index; Deep learning; Radiotherapy-induced fibrosis; Whole-breast irradiation.

MeSH terms

  • Breast / diagnostic imaging
  • Breast Neoplasms* / diagnostic imaging
  • Breast Neoplasms* / radiotherapy
  • Breast Neoplasms* / surgery
  • Female
  • Humans
  • Mastectomy, Segmental
  • Tomography, X-Ray Computed / methods