Anastrozole Replaces Adjuvant Tamoxifen

Jane Salodof MacNeil

December 04, 2003

Dec. 4, 2003 (San Antonio) — Switching estrogen-positive breast cancer survivors from adjuvant tamoxifen (Novaldex) treatment to anastrozole (Arimidex) significantly reduced the risk of death and relapse in a 426-patient Italian study.

After two or more years on tamoxifen and a median of an additional 28 months on tamoxifen or anastrozole, 10 of 218 patients who continued receiving tamoxifen had died of cancer compared with four of 208 patients who switched to anastrozole. In addition, of the patients who continued receiving tamoxifen, 10 patients had new cancers compared with five patients who switched to anastrozole.

Francesco Boccardo, MD, from Italy's National Cancer Institute and the University of Genoa, cautioned against rushing to conclusions, as he presented the results here today at the 26th Annual San Antonio Breast Cancer Symposium.

Nonetheless, he called the results "very strong" and said switching to an aromatase inhibitor such as anastrozole can raise a woman's chances of remaining event-free or progression-free. For women who switched in the study, the hazard ratio of relapse was 0.38; the hazard ratio of death was 0.18.

Dr. Boccardo told Medscape that he would not recommend switching every patient based on the evidence so far, but he does think it supports changing treatments in women who become intolerant of tamoxifen. The study needs to be repeated with other aromatase inhibitors, he added, suggesting that the benefits are likely an effect of the drug class. A recent study showed similar gains for another aromatase inhibitor, letrozole (Femara).

Session moderator Rita Kramer, MD, from Baylor School of Medicine and Methodist Hospital in Houston, Texas, told Medscape that Dr. Boccardo had presented "interesting data, but not information that should change the current standard of care."

Many questions still need to be answered about the sequencing of the five years of adjuvant therapy given for breast cancer, according to Dr. Kramer. "We don't really know how to sequence adjuvant therapy," she said, raising questions such as which women might be switched and after how many years on tamoxifen.

All of the women in the Italian study were postmenopausal, had been receiving 20 mg daily of tamoxifen for two or more years, and were recruited between March 1998 and October 2002. The investigators randomly assigned 218 women to continue with tamoxifen and 208 patients to switch to 1 mg of anastrozole daily. In both cases, treatment was to last up to five years.

The number of events — disease recurrences, second primary cancer, and deaths in the absence of progression — among the tamoxifen patients far outweighed those in the anastrozole group, according to Dr. Boccardo. These included subsequent diagnoses of contralateral breast cancer (2 vs. 1) and endometrial cancer (5 vs. 1); both groups had three cancers reported in other sites.

Gastrointestinal complaints were more common in the women who switched to anastrozole (14 incidents [6.3%] vs. 3 incidents [1.3%] in the women on tamoxifen), but that was expected, according to Dr. Boccardo. Increased cholesterol levels also occurred more often in those receiving anastrozole (18 cases [8.1%] vs. 6 cases [2.7%]), he said, but the reverse was true for gynecological changes. Two changes (0.9%) occurred in the group that switched compared with 16 changes (7.1%) in the women receiving tamoxifen.

The study received support from AstraZeneca, maker of anastrozole.

26th Annual San Antonio Breast Cancer Symposium: Abstract 3. Presented Dec. 3, 2003.

Reviewed by Gary D. Vogin, MD


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