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ASCO Highlights: Breast Cancer Prevention

By BCRF | June 13, 2016

Two new studies highlight the prevention of recurrence

Ten Years of Hormone Therapy Reduces Breast Cancer Recurrence Without Compromising Quality of Life  

Estrogen receptor (ER+) positive breast cancer is the most common form of breast cancer and when treated early has a 95% survival rate at five years. However, this disease can recur 10-20 years after diagnosis and successful treatment. Endocrine therapies – tamoxifen and aromatase inhibitors (AIs) have been shown to reduce the risk of recurrence of ER-positive breast cancer when therapy is continued for five years. Long-term studies are now showing that 10 years of endocrine therapy can further reduce risk. 

The MA.17R study was a double-blind, placebo-controlled trial to test the effectiveness of extending aromatase inhibitor (AI) treatment for an additional five years using letrozole. The trial included three cohorts of post-menopausal women with early stage ER-positive breast cancer, two of which had received prior tamoxifen and one that had no prior tamoxifen therapy. All patients had received four to six years of AI therapy. A total of 1,918 women were randomly assigned to receive either extended letrozole or placebo for an additional five years, for a total of ten years AI therapy. Median follow-up was 75 months (6.3 years). Presenting at the plenary session, Dr. Paul E. Goss (Massachusetts General Hospital) reported a significant decrease incidence of contralateral breast cancer in the extended letrozole group compared to placebo. There was no difference in overall survival, however, as an equal number of women, 100 in each group, died from their disease during the follow up period. In a separate quality of life analysis, there were no differences in quality of life between the two groups. 

In a press conference announcing the study results, Dr. Harold Burstein (Dana Farber Cancer Institute) noted “there will be tremendous interest in longer duration of AI therapy, but it will most likely be tailored to specific patient risk factors.” Discussant for the study Dr. Ian Smith (Royal Marsden Hospital, UK) commented that the difference in disease free survival (DFS) between the groups was 1.1%, but was nonetheless optimistic that the extended AI therapy could provide added benefit for women who were able to manage the side effects. 

The study results stimulated significant discussion on recommendations of extending AI therapy, with some in the audience feeling that the benefit did not outweigh the associated costs of AI- associated side effects, including increased risk of osteoporosis and bone fracture. Commenting in The New York Times, BCRF investigators Drs. Eric Winer and Lisa Carey present a cautious view of the study results emphasizing the need to consider patient risks, preferences and side effect tolerance. The study was conducted by the Canadian Cancer Trials Group in collaboration with US National Clinical Trials network. BCRF investigators Drs. Lois Shepherd, James Ingle, Hyman Muss, Julie Gralow, Antonio Wolff, Clifford Hudis and Eric Winer were co-authors on the study. 

Minority BRCA-Positive Breast Cancer Survivors Appear Less Likely to Receive Preventive Surgery

According to the National Cancer Institute, a woman with a BRCA mutation has an increased risk of breast and ovarian cancer by 45-65 percent and 20-40 percent, respectively. Prophylactic mastectomy and/or oophorectomy is recommended for BRCA mutation carriers and can dramatically reduce that risk of breast or ovarian cancer. An interim analysis of a study in a racially diverse group of more than 1,600 women found that African American women were significantly less likely to receive preventive surgery than White or Hispanic women. While acknowledging some limitations of the study, lead author, Dr. Tuya Pal (Lee Moffitt Cancer Center) commented in the ASCO Post, “It is imperative to understand why these disparities exist, so we can develop interventions to ensure that women with inherited disease make informed decisions about their cancer risk management. Listen to an interview of Dr. Pal with BCRF investigator, Lisa Carey here.