Actor Chhavi Mittal’s Tamoxifen story: Can the breast cancer drug cause fibroids?

What is tamoxifen and how can it affect the uterus?

Tamoxifen is a medicine commonly used to treat and prevent certain types of breast cancer. It works by blocking the effect of the female hormone oestrogen on breast cells. However, tamoxifen can act differently in the uterus. While it blocks oestrogen in breast tissue, it can have an oestrogen-like effect on the lining of the uterus. This may cause the lining to become thicker than normal and, in some women, can lead to problems such as unusual vaginal bleeding or spotting.

Most changes are not cancerous, but any new or unusual bleeding after menopause should be checked by a doctor.

So, can tamoxifen cause a fibroid?

It is safer to say that tamoxifen may contribute to fibroid growth or, in some women, the development of fibroids, rather than saying it definitively causes them. There are published reports of fibroid growth in women taking tamoxifen. But an individual fibroid cannot automatically be attributed to tamoxifen simply because it appeared after treatment.

Why does the distinction between “caused” and “associated with” matter?

Because fibroids are extremely common, and their development is influenced by several factors, including hormones and age. If someone taking tamoxifen develops a fibroid, there are two separate questions: Did the fibroid arise independently? Did tamoxifen contribute to its growth or make an existing fibroid larger? The second possibility has some scientific support. Establishing the first or second with certainty in one individual is much harder.

Is there evidence that tamoxifen can actually make fibroids grow?

The evidence is not enormous, but it exists. A study involving postmenopausal women taking tamoxifen found a statistically significant increase in average fibroid volume over follow-up; some women also developed new fibroids. The researchers interpreted the findings as supporting an estrogen-like, or “agonistic,” effect of tamoxifen on uterine tissue.

Do patients need to worry about developing fibroids?

Not necessarily. A uterine fibroid is a benign tumour of uterine muscle. Most fibroids are not cancerous. They can cause heavy periods, pelvic pressure, pain, or sometimes no symptoms at all. The issue with tamoxifen is broader than fibroids: because of its effects on uterine tissue, doctors also pay attention to abnormal endometrial changes.

Should women stop tamoxifen if they develop a fibroid?

Not without talking to your doctor. Tamoxifen can substantially reduce the risk of recurrence of certain breast cancers, so stopping it independently can have serious consequences. A newly discovered fibroid generally calls for an assessment of its size, location, symptoms and growth rather than an automatic decision to discontinue cancer treatment.

The appropriate response depends on the individual’s breast-cancer history and gynaecological findings.

What symptoms should a woman on tamoxifen take seriously?

New or unusual vaginal bleeding, spotting or discharge should be discussed with a doctor — particularly in women who are postmenopausal. A fibroid can itself cause bleeding, but tamoxifen users may also need evaluation for other uterine conditions. Tamoxifen also causes an increased risk of complications to the lining of the uterus and, rarely, of getting endometrial cancer, so any unusual bleeding should be objectively evaluated.