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Letrozole in advanced breast cancer: the PO25 trial

Henning T Mouridsen1

  • 1Department of Oncology, Rigshospitalet, Copenhagen University Hospital, Blegdamsvej 9, 2100, Copenhagen, Denmark. hmouridsen@rh.dk

Breast Cancer Research and Treatment
|March 3, 2007
PubMed

Insights

Letrozole significantly improves outcomes for post-menopausal women with advanced breast cancer compared to tamoxifen. This aromatase inhibitor offers longer progression-free survival and higher response rates, establishing it as a superior first-line endocrine therapy.

Area of Science:

  • Oncology
  • Endocrinology
  • Clinical Trials

Background:

  • Tamoxifen is a standard first-line endocrine therapy for advanced breast cancer.
  • However, over 50% of patients do not respond to tamoxifen, and responders have a short time to progression.
  • Third-generation aromatase inhibitors were developed as more effective alternatives.

Purpose of the Study:

  • To compare the efficacy of letrozole, a third-generation aromatase inhibitor, with tamoxifen as a first-line endocrine therapy for post-menopausal women with advanced breast cancer.

Main Methods:

  • The Femara Study PO25 randomized 907 post-menopausal women with advanced breast cancer.
  • Patients received either letrozole 2.5 mg (n=453) or tamoxifen 20 mg (n=454) orally daily until disease progression.
  • Patients could cross over to the alternative treatment upon progression.

Main Results:

  • Letrozole demonstrated a significantly longer median time to progression (TTP) than tamoxifen (9.4 months vs. 6.0 months; P<0.0001).
  • The objective response rate (ORR) was significantly higher with letrozole (32%) compared to tamoxifen (21%; P=0.0002).
  • Letrozole also showed significant improvements in early overall survival (OS) over the first 24 months.

Conclusions:

  • Letrozole is a highly effective first-line endocrine therapy for post-menopausal women with advanced breast cancer.
  • It offers significant improvements in objective response rate, time to progression, and early overall survival compared to tamoxifen.
  • Letrozole represents a superior treatment option for this patient population.

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