Among the women with midrange scores who were randomized, the hazard ratio for invasive disease-free survival with endocrine therapy alone compared with chemotherapy plus endocrine therapy (1.08) fell well within the predefined hazard ratio for noninferiority (1.322). The 9-year rate of invasive disease–free survival was 83.3% with endocrine therapy and 84.3% with chemotherapy plus endocrine therapy.
The groups had similar rates of freedom from distant recurrence (94.5% vs. 95.0%; hazard ratio, 1.10; P = .48) and distant or locoregional recurrence (92.2% vs. 92.9%; hazard ratio, 1.11; P = .33), and similar overall survival (93.9% vs. 93.8%; hazard ratio for death, 0.99; P = .89).
In exploratory analyses, there was an interaction of age and recurrence score (P = .004) whereby women aged 50 or younger derived some benefit from chemotherapy if they had a recurrence score of 16-20 (9% fewer invasive disease–free survival events, including 2% fewer distant recurrences) or a recurrence score 21-25 (6% fewer invasive disease–free survival events, mainly distant recurrences). “This is information that could drive some younger women who have a recurrence score in this range to accept chemotherapy,” Dr. Sparano said.
The 9-year rate of distant recurrence averaged 5% among the women with midrange scores overall. It was just 3% among the women with a low recurrence score given endocrine therapy alone, but it was still 13% among the women with a high recurrence score despite receiving both endocrine therapy and chemotherapy. The last finding may “indicate the need to explore potentially more effective therapies in this setting,” he proposed.
Dr. Sparano disclosed that he has a consulting or advisory role with Genentech/Roche, Novartis, AstraZeneca, Celgene, Lilly, Celldex, Pfizer, Prescient Therapeutics, Juno Therapeutics, and Merrimack; has stock or other ownership interests with Metastat; and receives research funding (institutional) from Prescient Therapeutics, Deciphera, Genentech/Roche, Merck, Novartis, and Merrimack. This study received funding primarily from the National Cancer Institute, National Institutes of Health. Additional support was provided by the Breast Cancer Research Foundation, Komen Foundation, and U.S. Postal Service Breast Cancer Stamp.
SOURCE: Sparano et al. ASCO 2018