Breast cancer drug may ease prostate cancer side effects

Men undergoing prostate cancer treatment commonly suffer side effects such as the growth of breast tissue or breast pain, but the breast-cancer drug tamoxifen may reduce the risk of these effects, a new review says.

Researchers looked at four studies of men with prostate cancer, and found that men whose treatments were supplemented with tamoxifen were less likely to have breast enlargement and breast pain than those not taking the drug.

For instance, six months after starting treatment, men who took tamoxifen were 10 percent less likely to have breast enlargement and 6 percent less likely to have breast pain compared with patients not receiving the drug, which counteracts the effects of estrogen on breast tissue.

Tamoxifen prevented these side effects about 20 percent better than other treatments, such as the drug anastrozole, which counteracts estrogen's effects in a different way, the researchers found.

The growth of breast tissue and breast pain has been cited as reasons why men stop their prostate cancer treatments, according to the study.

"If men know that there is a successful option for reducing the breast symptoms associated with treatment for prostate cancer, they may be more likely to see their doctor when symptoms of cancer first appear, and consequently reduce the number of unnecessary deaths," said lead study author Dr. Frank Kunath, of the University Clinic Erlangen in Germany.

Because testosterone can encourage prostate cancer growth, some treatments are aimed at suppressing testosterone production. As the body tries to produce even more testosterone to counter the drop, some of this testosterone is converted to estrogen, which causes breasttissue to develop and can lead to pain.

"When asking a patient to comply with a regime, you have to think about what the side effects are, and if they will drive a person to stop medication," said Dr. Freya Schnabel, professor and breast surgeon at New York University's Langone Medical Center, who was not involved in the study.

However, Schnabel said, the new review did not include data on how many men consider stopping or actually stop treatment because of these side effects. She added that truly calculating the negative impact of breast growth or breast pain was difficult.

It is logical that tamoxifen could reduce the effects of the estrogen produced during prostate cancer treatment, Schnabel said, though she cautioned that the researchers reviewed only four studies, and further research is needed.

"They're clearly not advocating that every man taking these medications should go on tamoxifen," she said, but the research suggests that taking the drug "may ameliorate their symptoms."

The study was published Aug. 27 in the journal BMC Medicine.

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