A Quantitative Evaluation of the Effects of Radiation Therapy on the Postsurgical Breast

Plastic and Reconstructive Surgery, April 2025

Key takeaways:

• Breasts continue to lose volume after radiation, averaging 20% loss after one year and 26% at five years

• Macromastia, diabetes, and smoking are associated with increased risk of volume loss

Background

• Breast-conserving therapy (BCT) is commonly utilized for treating early-stage breast cancer. However, subsequent radiation therapy (RT) can lead to breast changes that can be hard to predict.

• Previous literature indicates a range of volume loss post-BCT/RT, but there is limited quantitative data on how different factors (such as breast size, smoking history, and diabetes) correlate with such changes.

Objective

• This study aimed to quantify the extent of breast volume loss after BCT/RT and identify predictive factors associated with this loss in a cohort of patients.

Methods

• This retrospective study analyzed patients who underwent BCT with radiation for T1 tumors from 2005 to 2023 at UC San Diego Health.

• Exclusion criteria included previous breast surgery or radiation.

• Preoperative and postoperative breast volumes were calculated using craniocaudal mammograms and the formula π/3 * height * radius^2.

• The changes in breast volume over time (1, 3, and 5 years post-RT) were compared using paired t-tests, while multiple regression analysis assessed predictors for volume loss, including baseline breast volume, smoking status, diabetes, and chemotherapy received.

Results

• 115 patients were included

• On average, patients lost approximately 19.3% of their breast volume within one year after surgery, which increased to about 26.6% by year five.

• The study identified that:

  • Larger breast volumes experienced a greater percentage of volume loss over five years compared to those with smaller breasts.

  • Patients with a smoking history and diabetes exhibited significantly higher volume loss.

Conclusion

• The anticipated breast shrinkage from BCT/RT is around 20% in the first year, and approximately 26% by five years, varying based on the initial breast size and comorbid factors like diabetes and smoking.

Strengths and Limitations

• Strengths:

  • Data were collected over multiple years, offering a longitudinal view of breast volume changes.

  • The study highlights the importance of initial breast size and associated comorbidities as predictors of post-radiation outcomes.

• Limitations:

  • This study included only T1 tumors (<2 cm) and did not include details on reconstruction (i.e. volume displacement techniques).

  • Reliance on mammographic calculations for volumes may introduce variability. It is likely that radiated breasts are not as compressible, leading to underestimation of volume when using mammogram as the basis for volume.

  • The study could not correlate imaging data with qualitative assessments of aesthetics, limiting insights into patient satisfaction.

Clinical Relevance

• The study underscores the importance of anticipating breast volume changes post-BCT/RT, which is crucial for both patient education and surgical decision-making

• Long-term volume loss should be considered when evaluating candidacy for BCT