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Lasofoxifene Decreases Risk of Breast Cancer, Fractures Among Postmenopausal Women: Presented at SGBCC

By Mary Wessling

ST. GALLEN, Switzerland -- March 13, 2009 -- The third-generation selective oestrogen receptor modulator (SERM) lasofoxifene offers increased protection against breast cancer in postmenopausal women with osteoporosis and a high risk of breast cancer, researchers stated here at the St. Gallen Oncology Conferences: Primary Therapy of Early Breast Cancer International Conference (SGBCC).

The randomised, placebo-controlled Postmenopausal Evaluation and Risk-Reduction With Lasofoxifene (PEARL) study, presented on March 12, also showed that lasofoxifene treatment offered protection against vertebral and nonvertebral fractures, most forms of stroke, and coronary events and was effective in lowering cholesterol levels.

Trevor Powles, PhD, Parkside Oncology Clinic, Parkside Hospital, Wimbledon, United Kingdom, and colleagues randomised 8,556 otherwise healthy women aged 59 to 80 years equally to 2 treatment arms: lasofoxifene 0.5 mg/day versus placebo or lasofoxifene 0.25 mg/day versus placebo, for 5 years.

The primary endpoints were incidence of oestrogen receptor-positive (ER+) breast cancer and vertebral fracture (at 3 years) and nonvertebral fracture (at 5 years). Of the women, 77% completed the 5-year follow-up and 62% to 64% remained on the medication until study closure.

The positive effects of lasofoxifene accrued mostly with the 0.5-mg/day dose as opposed to the 0.25-mg/day dose.

There were 21 occurrences of ER+ breast cancer among the placebo group, 11 among women receiving the 0.25-mg/day dose, and only 4 occurrences among women receiving the 0.5-mg/day dose. For all invasive breast cancers, the figures were 20 among the placebo group, 16 among the 0.25-mg/day group, and 3 among the 0.5-mg/day group.

The women in the 0.5-mg/day group had a significantly reduced risk for vertebral fracture versus placebo at 3 years (hazard ratio [HR] = 0.58; 95% confidence interval [CI], 0.47-0.70). The risk of nonvertebral fracture at 5 years was also significantly reduced in the 0.5-mg/day group (HR = 0.76; 95% CI, 0.64-0.91) versus placebo.

Further benefit for the higher dose was found for stroke, excluding transient ischaemic attack (HR = 0.64; 95% CI, 0.41-0.99) and major coronary heart disease events (HR = 0.68; 95% CI, 0.50-0.93). However, there was a higher incidence of venous thromboembolic events (HR = 2.1; 95% CI, 1.20-3.60).

Endometrial thickening, uterine polyps, and fibroids were more common, but there was no increase in the endometrial atypia or cancer. Overall mortality was similar for women in the 0.5-mg/day group and women taking placebo (HR = 1.12; 95% CI, 0.80-1.56).

"It is the combination of benefits versus the lack of increased risk over other SERMs that is most significant about this study," said Dr. Powles after outlining the risks and benefits of first- and second-generation SERMs (tamoxifen and raloxifene) with lasofoxifene.

"We now can use agents with multiple outcomes to swing the balance toward the benefits versus the toxicity of treatment," he said.


[Presentation title: Five Year Results of a Randomised Placebo Controlled Trial of Lasofoxifene (PEARL) on the Incidence of ER Positive Breast Cancer in Postmenopausal Women With Osteoporosis. Abstract S12]

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