After primary therapy such as surgery and chemotherapy, a common practice to prevent the recurrence of breast cancer is to prescribe adjuvant tamoxifen for five to 10 years.

To get the most benefit from hormone therapy, patients need to take the full course of tamoxifen.

Women who complete the full course of hormonal therapy have a better survival rate than those who do not. It is also important to follow the treatment plan in terms of right timing, correct dosage and exact frequency.

Despite its acknowledged benefits, adherence to tamoxifen is less than ideal. The length of treatment coupled with side-effects can make it very tough for women to complete the course.

Approximately one in five patients who are prescribed adjuvant tamoxifen do not achieve optimal adherence during the first year of treatment, with a subsequent 7 per cent to 10 per cent discontinuation rate per year. By year four or five of treatment, the adherence rate is as low as 50 per cent.

The most serious hazards from taking tamoxifen, such as endometrial cancer and blood clots in the lungs, are very rare. However, menopausal symptoms (such as hot flushes, vaginal dryness, headache, anxiousness, loss of interest in sex) are common in women who take this treatment.

Affected women should talk to their doctor or nurses about ways to ease these side effects.

If a person has a busy work schedule and trouble remembering to take the drug, a pillbox or setting an alarm or downloading an app may help.

There is no need for people to panic if they only miss one or two doses, but they should continue taking the drug as long as it is prescribed by their doctor.

Carmen W. H. Chan, professor; Judy Y. W. Chan, research associate, Nethersole School of Nursing, Chinese University of Hong Kong