• Posted March 31, 2025

Breasts Can Shrink Following Cancer Surgery, Radiation

Breast-conserving therapy for breast cancer might not conserve as much as previously thought, a new study suggests.

Women’s breasts can shrink considerably after they’ve undergone radiation therapy and lumpectomy for their early-stage breast cancer, researchers reported March 27 in the journal Plastic and Reconstructive Surgery.

"Our findings suggest that women undergoing (breast conserving therapy with radiation therapy) may lose approximately 20% of breast volume within a year, with continued reductions through five years," senior researcher Dr. Chris Reid, an assistant professor of surgery at the University of California-San Diego, said in a news release.

"Anticipating these changes may help guide patient expectations and assist surgical planning to restore women after breast cancer treatment,” he added.

Many women with early-stage breast cancers prefer lumpectomy and radiation therapy for their treatment, researchers said. It offers survival rates similar to those of mastectomy, while preserving the breast.

But radiation therapy is known to have side effects on breast tissue, including scarring and shrinkage, researchers noted.

To see whether this winds up being noticeable, researchers measured changes in breast volume among 113 women who underwent breast-conserving treatment for early-stage breast cancer between 2005 and 2023.

The women’s breast volume initially decreased by an average of 9% after the tumor was removed, researchers found.

After a year, the average decline in breast volume was 19%, results show, in addition to the tissue removed at surgery. By five years, the average decrease in breast size was more than 26%.

Women with larger breasts and relatively smaller tumors — measuring less than 10% of their breast volume — wound up with greater shrinkage, approaching 30% on average compared to nearly 22% for women with smaller breasts.

The greater loss in size among women with larger breasts raises concerns about breast asymmetry, a common concern after breast-conserving treatment, Reid said.

"Anticipating these changes may help guide patient expectations and assist surgeons in planning reconstructive procedures to attain symmetry posttreatment," Reid said.

Researchers said future research should look into how different cancer treatments affect breast size.

More information

The American Cancer Society has more on breast-conserving surgery.

SOURCE: Wolters Kluwer Health, news release, March 27, 2025