Forever is more than enough.
Top Line: What’s the optimal duration of endocrine therapy for women with breast cancer?
The Study: The easy answer is forever. We’ve seen that, at 20 years, the rates of breast cancer mortality among survivors of hormone receptor-positive breast cancer are pretty sobering. With no expiration date for breast cancer recurrence, the obvious answer is to continue endocrine therapy indefinitely, right? NSABP B-42 was a large phase 3 trial that randomized women to 5 additional years of extended aromatase inhibition or placebo. It enrolled nearly 4000 post-menopausal women with stage I-IIIA disease with no progression after 5 years on endocrine therapy. After a median follow-up of >6 years (or >11 years from diagnosis) there was no improvement in disease-free survival with extended aromatase inhibition. Was there a benefit for breast cancer recurrence? Well, of course. The problem is that 10 years after a diagnosis, competing causes of death can overwhelm the breast cancer benefits and may even be amplified by extended therapy. Looks like we need more than a calculator or genetic test for risk of late recurrence; we also require one for competing mortality. In the end, the answer really isn’t that easy.
Bottom Line: Despite decreasing breast cancer recurrence, extended aromatase inhibition for all postmenopausal women does not improve disease-free or overall survival possibly due to its impact on competing causes of mortality. | Mamounas, Lancet Oncol 2018
The Study: The easy answer is forever. We’ve seen that, at 20 years, the rates of breast cancer mortality among survivors of hormone receptor-positive breast cancer are pretty sobering. With no expiration date for breast cancer recurrence, the obvious answer is to continue endocrine therapy indefinitely, right? NSABP B-42 was a large phase 3 trial that randomized women to 5 additional years of extended aromatase inhibition or placebo. It enrolled nearly 4000 post-menopausal women with stage I-IIIA disease with no progression after 5 years on endocrine therapy. After a median follow-up of >6 years (or >11 years from diagnosis) there was no improvement in disease-free survival with extended aromatase inhibition. Was there a benefit for breast cancer recurrence? Well, of course. The problem is that 10 years after a diagnosis, competing causes of death can overwhelm the breast cancer benefits and may even be amplified by extended therapy. Looks like we need more than a calculator or genetic test for risk of late recurrence; we also require one for competing mortality. In the end, the answer really isn’t that easy.
Bottom Line: Despite decreasing breast cancer recurrence, extended aromatase inhibition for all postmenopausal women does not improve disease-free or overall survival possibly due to its impact on competing causes of mortality. | Mamounas, Lancet Oncol 2018
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