For men who experience a PSA recurrence (rise in prostate-specific antigen levels) after radiation therapy for prostate cancer, hormone therapy given intermittently (with breaks) appears to be as effective as hormone therapy given continuously. These results were presented at the 2011 Genitourinary Cancers Symposium.

Androgen deprivation therapy is designed to block testosterone from stimulating the growth of hormone-dependent types of prostate cancer. Because continuous androgen deprivation therapy produces side effects such as osteoporosis, hot flashes, and loss of libido, and because many prostate cancers eventually become resistant to hormonal therapy, researchers continue to explore alternatives.

Intermittent androgen suppression (IAS) is one such alternative. It involves the administration of hormonal therapy until a sufficient treatment response has been achieved, followed by a period of no treatment. The cycle is repeated as needed. IAS may reduce side effects and delay hormone resistance.

In order to assess the effects of IAS among men who experience an increase in PSA after radiation therapy for prostate cancer, researchers evaluated 1,386 men. Half the patients were treated with continuous androgen deprivation and half were treated with IAS. IAS was delivered for eight months at a time, and was restarted if PSA levels off treatment exceeded 10 ng/ml.

During follow-up, patients assigned to IAS were on treatment (receiving hormone therapy) 27% of the time.

The trial was stopped early when it became apparent that overall survival with IAS was no worse than with continuous androgen deprivation therapy.

  • Overall survival was 8.8 months among patients treated with IAS and 9.1 months among patients treated with continuous androgen deprivation.
  • The IAS group had more prostate cancer-related deaths than the continuous androgen deprivation group, but fewer deaths from other causes.
  • The IAS group experienced fewer hot flashes than the continuous androgen deprivation group. The frequency of other side effects did not differ between the groups.

In terms of overall survival, these results suggest that intermittent hormone therapy is as effective as continuous hormone therapy. Providing hormone therapy only intermittently may improve quality of life and reduce costs for men with prostate cancer.

Reference: Klotz L, O’Callaghan J, Ding K et al. A phase III randomized trial comparing intermittent versus continuous androgen suppression for patients with PSA progression after radical radiotherapy: NCIC CTG PR.7/SWOG JPR.7/CTSU JPR.7/UK Intercontinental Trial CRUKE/01/013. Presented at the 2011 Genitourinary Cancers Symposium. Abstract 3.

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