UT MD Anderson study develops clinical tool to predict radiation benefit for older women with breast cancer

Results address management decisions in growing population

MD Anderson News Release 06/25/12

A new nomogram, or clinical model, from The University of Texas MD Anderson Cancer Center demonstrates accuracy in predicting the benefit of radiation therapy in older women with breast cancer.

The findings, published in the Journal of Clinical Oncology, may offer clinical guidance to physicians, providing information to help determine which elderly breast cancer patients will likely benefit from radiation therapy.

Establishing indications for radiation therapy is critical as the U.S. population ages, said Benjamin Smith, M.D., assistant professor in MD Anderson's Department of Radiation Oncology. Notably, a 57 percent increase in breast cancer diagnoses in older women is projected during the next two decades.

"As our population ages, we'll see a substantial increase in older women with breast cancer," Smith said. "The more we can marry best evidence with treatment, the better we can help our patients."

"We thought it was relevant and interesting to look at the risk of mastectomy after initial treatment for breast cancer, see if radiation therapy made a difference and then develop a tool to individualize recommendations based on a person's risk profile," Smith continued.

For the retrospective study, Smith and his colleagues used the Surveillance, Epidemiology, and End Results (SEER) registry, compiled by the National Cancer Institute, to identify 16,092 women ages 66 -79 treated with conservative surgery between 1992 - 2002. The primary outcome was mastectomy-free survival (MFS) at five and 10-year periods, as mastectomy is typically used to treat a recurrence in the breast, Smith said.

Most patients had tumors less than or equal to 2.0 cm, while 84 percent of patients had clinical or pathologic node-negative disease.

Nomogram Development and Results
The tool employs readily available clinical and pathologic data including age, race, tumor size, estrogen receptor status and receipt of radiation therapy, which are all predictive of time to mastectomy.

In total, 505 patients underwent a subsequent mastectomy for disease recurrence, yielding five and 10- year MFS estimates of 98.1 percent and 95.4 percent respectively. In addition to providing baseline estimates of MFS, the nomogram presents individualized estimates of potential benefit from radiation therapy.

For example, a 75-year-old woman with a 1.5 cm ER-positive tumor and node-negative disease who underwent radiation therapy, yields an estimated 10-year MFS of 97 percent. However, if this same patient did not receive radiation therapy, the 10-year MFS rate would be 95 percent, suggesting radiation confers limited benefit.

One limitation to the study, notes Smith, is the patient population's lack of diversity. The nomogram's predictive value may be less precise for patients of non-white race.

"Although no nomogram is perfect, it's a step forward to actually have a validated model based on the outcomes of 16,000 patients," Smith said. "We validated the model internally and found its predictive properties were comparable to other models widely used in clinical breast cancer medicine."

Further prospective studies are needed to more accurately determine the risk of recurrence for different subgroups of older populations with early breast cancer. In time, there are plans to make the nomogram available on MD Anderson's website.

In addition to Smith, coauthors on the study include: Thomas Buchholz, M.D; Karen Hoffman, M.D., Jeffrey Albert, M.D., all of the Department of Radiation Oncology; Sharon Giordano, M.D., Department of Breast Medical Oncology; Yu Shen, Ph.D., Diane Liu, I-Wen Pan, Ph.D., and Ya-Chen Tina Shih, Ph.D., Department of Medicine at the University of Chicago.

The study was funded through research grants from Varian Medical Systems, the U.S. Department of Health and Human Services, National Cancer Institute, the Cancer Prevention and Research Institute of Texas and the University of Chicago Comprehensive Cancer Center Women's Board.

Smith receives research funding from Varian Medical Systems.