A new study published in the New England Journal of Medicine has found that breast cancer can return 20 years after diagnosis. This major study which was funded by Cancer Research UK gathered data from 88 clinical trials involving over 60,000 women who had been diagnosed with breast cancer sensitive to hormones and prescribed 5 years of hormonal therapy, like tamoxifen or an aromatase inhibitor. The study showed that disease may recure up to 15 years after hormonal therapy been discontinued, 20 years after their initial diagnosis. This suggests that hormonal treatments may need to be continued for even longer than 5 years to reduce the risk of late recurrence.
In my opinion, this is an important study but has its own limitations. We have always known that breast cancer may return many years after initial diagnosis and it is not a randomised clinical trial which means that biased results cannot be excluded. The other factor which has to be considered when extending hormonal therapy is their side effects. Tamoxifen, for example, increases the risk of deep vein thrombosis while aromatase inhibitors may cause osteoporosis. Patients who want to take hormonal therapy for more than five years should carefully discuss the risk and benefits with their oncologist.
It is very important that all women who have had treatment for breast cancer in the past remain vigilant and always check for signs of recurrence of breast cancer. They should always speak to their GPs or breast consultants if they have any concerns, no matter how long it is after their initial diagnosis.
Pan H, Gray R, Braybrooke J, Davies C, Taylor C, McGale P, Peto R, Pritchard KI, Bergh J, Dowsett M, Hayes DF; EBCTCG. 20-Year Risks of Breast-Cancer Recurrence after Stopping Endocrine Therapy at 5 Years. N Engl J Med. 2017;377(19):1836-1846. doi: 10.1056/NEJMoa1701830. PMID: 29117498