A new study has found that breast-conserving therapy (BCT)—a common treatment for early-stage breast cancer—can lead to significant breast shrinkage over time, especially when combined with radiation therapy (RT).
The study, published in Plastic and Reconstructive Surgery, shows that women may lose up to 20% of breast volume within the first year, with the shrinkage continuing for up to five years.
“Knowing these changes can happen is important,” says Dr. Chris Reid from the University of California San Diego, who led the study.
“It helps doctors and patients plan for what to expect after treatment, including any needed reconstruction.”
What is breast-conserving therapy?
Breast-conserving therapy is often the preferred treatment for early-stage breast cancer. It usually involves removing the tumor through a lumpectomy, followed by radiation therapy.
This approach offers similar survival rates to a full mastectomy, with the added benefit of keeping most of the breast and generally better emotional and physical recovery.
However, radiation can cause changes to the breast tissue over time, such as shrinkage and hardening. These effects are due to tissue damage and scarring caused by radiation.
Dr. Reid and his team studied 113 women who received BCT and RT between 2005 and 2023. Using mammograms, they measured breast volume before treatment, shortly after surgery, and up to five years later.
Right after surgery, breast size dropped by an average of 9.2%, which is expected due to the removal of the tumor. However, the study found that breast shrinkage continued long after surgery, mostly due to radiation.
After one year, breast volume had decreased by an average of 19.3%. By five years, the average total shrinkage reached 26.6%. The shrinkage happened gradually each year and affected all patients in the study.
Factors that increase shrinkage
Women with larger breasts and smaller tumors experienced more shrinkage—about 29.5%, compared to 21.7% in others. Other risk factors included:
- Smoking
- Diabetes
- Receiving chemotherapy along with radiation
Breast shrinkage can lead to asymmetry, where the treated breast is noticeably smaller than the other. This can impact a woman’s self-image and quality of life. That’s why it’s important for doctors to talk to patients about this possibility before treatment.
“Understanding these changes can help surgeons plan better reconstruction or cosmetic procedures to restore balance,” Dr. Reid explains.
The researchers hope this study will lead to better ways to measure and manage breast volume changes in the future, helping women feel more informed and supported throughout their treatment journey.
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