How Long Do You Need to Take Tamoxifen After Breast Cancer?

Most people take tamoxifen for five to ten years after a breast cancer diagnosis. Five years has been the standard for decades, and for many women with hormone receptor-positive cancer, going on to ten years lowers the chance of the cancer coming back. Which one is right for you depends on your recurrence risk, whether you’ve been through menopause, and how you’re tolerating it. Tamoxifen only works for hormone receptor-positive cancer.

Dr. Sandeep Nayak, who provides Cancer treatment in Bangalore, says patients hear “five to ten years” and feel their heart sink. “It sounds like forever. But it’s a small tablet a day, and it’s lowering the chance of the cancer coming back, which is the whole point. I don’t fix the number on the first visit. We look at the stage, the tumour, your age and menopause status, and how you’re feeling on it at five years. And if side effects are getting in the way, tell us. There’s often something we can do, and stopping quietly on your own is the one thing I’d ask you not to do.”

The standard plan has a few common versions:

• Five years is the standard. Most women start after surgery, and after chemotherapy or radiation if they need it, and take a tablet once a day for five years.
• Ten years may be offered when risk is higher. Two large trials, ATLAS and aTTom, found that continuing to ten years lowered recurrence and breast cancer deaths in women with hormone receptor-positive cancer. In ATLAS, that worked out to about three fewer recurrences and about two fewer breast cancer deaths for every hundred women.
• If you’re postmenopausal, there are other routes. After five years you might carry on with tamoxifen, or switch to a different type of drug called an aromatase inhibitor, for a total of up to ten years. Some people switch after two or three years. Aromatase inhibitors only work after menopause, so premenopausal women usually stay on tamoxifen.
• Shorter courses exist too. Tamoxifen taken after DCIS, or to lower risk in high-risk women, is usually five years. Our breast cancer treatment in Bangalore page explains the options.

The number isn’t fixed. These are the things that move it up or down:

• Your risk of recurrence. A larger tumour, cancer in the lymph nodes, or a higher grade all push toward a longer course. A small, low-risk cancer can sensibly stop at five years.
• How your body copes with it. Hot flushes, joint aches and vaginal dryness are common. The extra risks of going to ten years are small but real: cancer of the womb lining and blood clots are a little more common. In ATLAS, womb lining cancer was 3.1% against 1.6%, and lung clots were 0.63% against 0.32%. So report any unusual vaginal bleeding, leg swelling or sudden breathlessness straight away.
• Stopping early costs you something. The benefit comes from finishing the course, and many women stop because of side effects. Talk to your team first. There are ways to ease them, or to switch to another drug. Our oncology team can walk you through it.
• Pregnancy plans and other medicines. You shouldn’t get pregnant on tamoxifen, so ask about timing if that’s on your mind. Tell your doctor about every medicine you take, because some antidepressants can weaken its effect.

Two women with hormone receptor-positive cancer can end up on quite different plans. A few things decide it:

• The tumour’s features. The hormone receptor status is the starting point, and the grade, size and HER2 status add detail. A genomic test can sharpen the picture, and our precision oncology service covers that testing.
• The lymph nodes and the stage. Cancer in the nodes, or a more advanced stage, makes a longer course more attractive.
• Menopause and age at diagnosis. This often decides between tamoxifen and an aromatase inhibitor, and whether the ovaries need suppressing as well.
• Your general health and tolerance. A history of blood clots, womb problems, bone thinning or other medicines can change what’s safe.
• A proper check-in at five years. The decision to stop or carry on is usually made then, with your doctor, using everything that’s changed since you started.