A pair of studies suggest that aromatase inhibitors and bisphosphonates can each improve survival for postmenopausal women with early breast cancer.
In two independent meta-analyses that compiled data from more than 50,000 patients, aromatase inhibitors (AIs) and bisphosphonates were each shown to improve survival in women with early postmenopausal breast cancer. The two studies were published in Lancet.
In the first study, researchers found that AI-based therapy for 5 years, compared with 5 years of tamoxifen alone, lowered 10-year breast cancer mortality (12.1% vs 14.2%, P = .009). The 10-year recurrence risk was 19.1% in the AI group and 22.7% in the tamoxifen group. AI treatment also lowered the risk of cancer recurrence by about 30%, proportionally, compared with tamoxifen alone during treatment, though not afterward.
Women who took an AI for 5 years compared to no endocrine therapy would have a 40% reduced risk of dying from their breast cancer in the 10 years after starting therapy, “a significantly greater protection than that offered by tamoxifen,” said Dowsett in a statement.
Comparing 5 years of an AI to 2–3 years of tamoxifen followed by an AI until year 5, risk of recurrence was significantly lowered only in the first years when the therapies differed (P = .002) and was similar thereafter.
Bone fractures are a potential side effect of AIs, and the bone health of women on AI therapy should be monitored. Use of bisphosphonates may lower the risk of fractures, according to the study authors.
Since the readout of the trials included in the meta-analysis, 10 years of either tamoxifen or 5 years of tamoxifen followed by an AI has been shown to decrease cancer recurrence, and there is currently no data on whether an AI for longer than 5 years may provide an even greater benefit, wrote Erica L. Mayer, MD, and Harold J. Burstein, MD, PhD, of the Dana-Farber Cancer Institute, in an accompanying commentary.
The second study, an analysis of 18,766 women in 26 randomized trials, demonstrated that the use of bisphosphonates, typically used to treat osteoporosis, reduced the risk of dying from breast cancer by 18% in the first 10 years after diagnosis (P = .04; compared with no bisphosphonate). Addition of bisphosphonates reduced the 10-year recurrence of cancer in the bone (6.6% vs 8.8%, P = .0002).
These benefits were regardless of tumor size, the type of bisphosphonate used, the duration of therapy, whether the patient had lymph node involvement, or had estrogen receptor–positive disease.
Still, bisphosphonates did not lower the risk of developing breast cancer in the opposite breast, the analysis showed.
“Our results show that adjuvant bisphosphonates in postmenopausal women prevent around a quarter of bone recurrences and one in six of all breast cancer deaths in the first decade of treatment,” said study author Robert Coleman, of the University of Sheffield in the United Kingdom. “These simple, well tolerated treatments should now be considered for routine use in the treatment of early breast cancer in women with either a natural or medically induced menopause to both extend survival and reduce the adverse effects of cancer treatments such as the AIs on bone health.”