Low MI Risk With Aromatase Inhibitors in Community-Treated Breast Cancer Patients
Major Finding: In the first study, the AI-treated patients had a significant reduction in risk of stroke (P = .004), compared with breast cancer patients on no endocrine treatment. In the second study, the absolute increase in risk associated with AIs was quite small (0.8% in excess of the 3.4% rate with tamoxifen). The number of women who would need to be treated with an AI instead of tamoxifen in order to have one additional patient experience a cardiovascular event was 132.
Data Source: First study: A case-control study involving 44,463 women diagnosed with early breast cancer in 2001-2007 and an equal number of closely matched controls obtained from a database of 30 million privately insured individuals. Second study: A meta-analysis of seven randomized trials comparing aromatase inhibitors with tamoxifen.
Disclosures: Dr. Ligibel and Dr. Amir declared having no relevant financial interests; Dr. Ligibel’s study was funded by the National Cancer Institute.
The risk of venous thromboembolism in the meta-analysis was 45% lower with AIs than tamoxifen (P less than .001). The absolute risk was 1.6% in the AI group, compared with 3.1% with tamoxifen, for a number-needed-to-harm of 69.
Fractures were consistently more common with AI therapy, with a 47% increased relative risk (P less than 0.001) and an absolute risk of 7.5% as compared to 5.2% with tamoxifen. The number-needed-to-harm via an AI was 46 patients.
There were no differences between the two groups in terms of cerebrovascular events or emergence of second cancers, with the exception of endometrial carcinoma, which was 66% less likely in the AI group and had a number-needed-to-harm of 250.
The risk of death unrelated to recurrent breast cancer was closely similar with AIs and tamoxifen. However, there was a strong trend for fewer deaths without recurrence in patients who underwent switching, either from an upfront AI to tamoxifen or vice versa.
"This suggests that there may be side effects that build up the longer a woman is on a certain drug, and therefore – and this is strictly hypothesis generating – that switching from one agent to another may be the best way to avoid these toxicities," Dr. Amir concluded.
Dr. Amir declared having no relevant financial interests. So did Dr. Ligibel, whose study was funded by the National Cancer Institute.
