Managing the side effects of bicalutamide monotherapy

In Europe, bicalutamide monotherapy with a dose of 150 mg/d is a widely used option for prostate cancer patients who wish to avoid the consequences of standard androgen deprivation using an LHRH agonist such as leuprolide acetate. However, bicalutamide induces gynecomastia (enlargement of the breasts) and mastalgia/mastodynia (pain in the breasts) in most patients.

Once-daily tamoxifen therapy is generally considered to be a safe and effective method of preventing such side effects of bicalutamide monotherapy without affecting antitumor activity. However, there have always been concerns about but interactions between bicalutamide and tamoxifen.

Bedognetti et al. have reported on the use of weekly (as opposed to daily) tamoxifen administration as a means to reduce patients’ exposure to tamoxifen.

Between December 2003 to February 2006, 80 patients with localized/locally advanced or biochemically recurrent prostate cancer who were also candidates for bicalutamide monotherapy were randomized to receive one of two different schedules of tamoxifen:

  • Current standard therapy with 20 mg tamoxifen once daily (n = 41)
  • An investigational regimen with 20 mg tamoxifen once weekly after an initial “run in” of tamoxifen once daily for 8 weeks (n = 39).

The results of their study are as follows:

  • Median follow-up was 24.2 months.
  • Three patients in the weekly group and one in the daily group discontinued treatment because of adverse events.
  • Gynecomastia developed in 13/41 patients (31.7 percent) in the daily group and in 29/39 patients (74.4 percent) in the weekly group, and it was more severe in patients on tamoxifen.
  • Mastalgia occurred in 5/41 patients (12.2 percent) in the daily group and in 18/39 patients (46.1 percent) in the weekly group.
  • There were no major differences between treatment groups relative to sexual function scores and incidence and severity of adverse events.
  • No differences between groups in PSA behavior or disease progression had been detected at the time of submission of this report.

The authors conclude that tamoxifen 20 mg once weekly (even after a run-in period of 8 weeks on daily tamoxifen) is not as effective as tamoxifen 20 mg once daily in preventing the incidence and severity of bicalutamide-induced breast events and they state that “The safety and efficacy of tamoxifen at the common daily dose of 20 mg for the prophylaxis of bicalutamide-induced breast events were confirmed.”

One Response

  1. Additional information regarding preventing this side effect of bicalutamide/Casodex can be found if you click here. Then scroll down to “Breast Enlargement.”

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