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Breast Cancer Adjuvant Therapy Benefit Can Wax and Wane Over Time

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Key Points

  • 19 breast cancer adjuvant therapy clinical trials were evaluated for relative benefit, defined as the percentage by which they reduced recurrence and death among study participants.
  • Researchers found time-varying treatment effects of adjuvant therapies in nearly half of the trials (9 of 19).
  • Researchers suggest further study is needed to understand the full benefits and/or disadvantages of adjuvant therapies. 

After breast cancer surgery, women are prescribed adjuvant therapies such as chemotherapy and endocrine drugs to reduce the risk of the cancer returning. It has been assumed that the treatment effects of these therapies remain constant over time, but a new study from the Cancer Therapy & Research Center at The University of Texas Health Science Center at San Antonio suggests the opposite is true.

The study, published by Jatoi et al in the Journal of the National Cancer Institute, looked at 19 breast cancer adjuvant therapy clinical trials of the National Surgical Adjuvant Breast and Bowel Project (NSABP). Therapies were evaluated for relative benefit, defined as the percentage by which they reduced recurrence and death among study participants.

Study Findings

Researchers found time-varying treatment effects of adjuvant therapies in nearly half of the trials (9 of 19). “In some trials, the benefit diminished at specific points of time after surgery,” said Ismail Jatoi, MD, PhD, FACS, Dale H. Dorn Chair in Surgery in the School of Medicine at the UT Health Science Center and Professor and Chief of the Division of Surgical Oncology and Endocrine Surgery. “In other trials, there was no benefit early on, but then there was a delayed benefit that emerged more than 1 year after surgery.”

In one clinical trial, the researchers found that a regimen provided initial benefit, but then a subsequent disadvantage. The findings may change the way oncologists talk to their patients about effects of treatments they are receiving, Dr. Jatoi said.

“We are seeing more and more long-term survivors of breast cancer who had these treatments many years ago,” Dr. Jatoi said. “The question is, if these treatment effects have waned, should we consider extended adjuvant treatment regimens for the long term in some patients.”

Adjuvant therapy trials should be designed and interpreted with this in mind, Dr. Jatoi said.

The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.


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