Aromatase inhibitors in the extended treatment of early-stage breast cancer

Photo of a woman lost in thought (PantherMedia / Peter Werner)

In the "extended" treatment approach, tamoxifen is used for five years, and then an aromatase inhibitor is taken.

In 2016, the Institute for Quality and Efficiency in Health Care (IQWiG, Germany) looked into the advantages and disadvantages of aromatase inhibitors in the extended treatment of early-stage breast cancer in women.

The Institute compared the effects of aromatase inhibitors used in this way with the effects of no treatment or a placebo treatment. The Institute only found one relevant study, looking at the aromatase inhibitor letrozole. A total of 5,187 women participated in this study. They had all already been through the menopause. Half of the women were given 2.5 mg letrozole per day for five years, and the other half took a placebo (fake medication). All of the women had previously been treated with tamoxifen for five years. The results are described below.

What are the advantages of extended treatment with aromatase inhibitors?

  • Life without recurrences: The study provided weak evidence that letrozole can prevent recurrences: After two years, about 9 out of 100 women who had the placebo treatment had got breast cancer again or had passed away, compared to only about 6 out of 100 women who had treatment with letrozole.

What are the disadvantages of extended treatment with aromatase inhibitors?

  • Treatment stopped due to side effects: The study suggests that women who are treated with letrozole are more likely to stop their treatment due to side effects: About 4 out of 100 women who only had a placebo treatment stopped their treatment due to side effects, compared to about 5 out of 100 women who took letrozole.

No difference

  • Life expectancy: The study found no differences between letrozole and the placebo in terms of life expectancy.
  • Severe side effects: There was also no difference in terms of severe side effects. About 15 out of 100 women experienced these during the treatment.

What remains unanswered?

  • Breast-cancer-related problems and quality of life: The study didn't include any suitable data concerning the effects of letrozole on the women's breast-cancer-related problems or quality of life.
  • It also didn't provide any suitable data about how letrozole affects the following serious side effects of the treatment: