Source: Neuroimaging Clin N Am  |  Posted 6 years ago

By Ed Susman

DENVER, CO -- October 19, 2005 -- Women who are premenopausal when they are diagnosed with breast cancer and women who have four or more positive breast nodes should continue on aromatase inhibitors after they have completed 5 years of tamoxifen following curative surgery.

But, in a new analysis, doctors suggest that other women with low risk factors for recurrence of cancer -- perhaps most women eligible for breast conserving therapy --- may not need to take aromatase inhibitors, said researchers at the 47[^]th[] annual meeting of the American Society for Therapeutic Radiology and Oncology (ASTRO).

"About 70% of women probably would not get clinical benefit from taking another 5 years of aromatase inhibitors," said Gary Freedman, MD, a member of the radiation oncology department at Fox Chase Cancer Center.

The Canadian MA-17 trial showed that the aromatase inhibitor letrozole (Femara) can cut their risk of breast cancer recurrence in half among women who take the drug for 5 years after finishing a 5-year course of tamoxifen, Dr. Freedman said.

"But these aromatase inhibitors are very expensive and there is a large co-payment even if you have insurance," Dr. Freedman said in an interview. "There is a very real cost issue that is not inconsequential. Plus there are side effects, chiefly an increased risk of fractures."

"Is it worth it for all women who complete 5 years of tamoxifen to take these drugs?" HE asked. "Our analysis suggests that at least for low-risk women, it may not be."

Dr. Freedman and his colleagues undertook a study of 471 women who had no signs of breast cancer after taking tamoxifen for 5 years. Before starting tamoxifen, all the women received breast-conserving surgery, removal of affected lymph nodes, and radiation. None were given an aromatase inhibitor.

After an average of 8 years, cancer came back in 26 women (5.5%), and another 10 women (2.1%) developed tumors in their originally unaffected breasts.

Dr. Freedman said that the findings indicate that 100 women would have to be treated to prevent 2 relapses -- a tradeoff they said was generally considered too small given the risks and costs of aromatase inhibitors. "In clinical practice, a benefit of at least [3 in 100] is commonly used to select patients for chemotherapy," he said.

However, Dr. Freedman said the analysis of the study did pinpoint two groups of women who appear to benefit from aromatase inhibition. They included women who at the time of diagnosis were premenopausal had nearly a 3-fold risk of recurrence, and therefore would fall into the category of having greater than a 3% risk of cancer relapse. That risk was significant at the P = .011 level, he said.

He also found that women with four or more positive lymph nodes had more than a 4-fold risk of breast cancer recurrence. That risk was statistically significant at the P = .0014 level.

On the other had, Dr. Freedman said women over age 60 and those who have co-morbidities would probably not benefit from the drugs. During the study period, many of these women died from causes other than breast cancer in the 10 years after starting tamoxifen, he said. "Whether or not they took an aromatase inhibitor would have had no impact on their survival," he said.

Richard Poetter, MD, Professor of Radiation Oncology, Clinic for Radiotherapy and Radiobiology, University of Vienna, Vienna, Austria, commented, "Retrospective studies such as this one generate hypotheses that need to be investigated. However, until such time this type of study is completed, patients and their doctors need to discuss the pros and cons of using these drugs, some of which are quite expensive."

[Presentation title: Selection of Breast Cancer Patients for an Aromatase Inhibitor after Radiation and 5 years of Tamoxifen. Abstract 2019]