Aromatase Inhibitors More Effective Than Tamoxifen in Treating Breast Cancer, Study Finds
Medications in a class called aromatase inhibitors, which block hormones, are more effective in the treatment of breast cancer than tamoxifen, reduce the number of recurrences of the disease and eliminate the most severe side effects of tamoxifen, according to a study published on Wednesday in the Lancet, the New York Times reports. Aromatase inhibitors block an enzyme used by tissue in the body to produce estrogen, which can prompt tumor development, but does not eliminate production of the hormone in the ovaries. As a result, such medication might not prove effective in women who have not entered menopause (O'Connor, New York Times, 12/9).
About 75% of postmenopausal breast cancer patients and about 20% of premenopausal patients have estrogen-sensitive tumors (Maugh, Los Angeles Times, 12/9). The study used Arimidex, an aromatase inhibitor manufactured AstraZeneca that is one of three such medications on the market. Arimidex had 2004 sales of $255 million as of October, compared with $211.6 million in 2003. Tamoxifen, which is manufactured by AstraZeneca and also available in generic form, had 2004 sales of $52.3 million as of October, compared with $177.9 million in 2003, according to IMS Health (New York Times, 12/9).
The study, which was funded by AstraZeneca and presented at the San Antonio Breast Cancer Symposium, included 9,366 postmenopausal women with early, estrogen-sensitive breast cancer who took either tamoxifen or Arimidex (Stein, Washington Post, 12/9). The study, which lasted five years and included participants from 20 nations, found that participants who took Arimidex reduced their risk for spread of cancer by 14% and for development of a tumor in the other breast by 42% (New York Times, 12/9). In addition, participants who took Arimidex increased disease-free survival by 10% and raised the time to breast cancer recurrence by 20%, the study found (Los Angeles Times, 12/9). The study also found that Arimidex reduced the risk for breast cancer recurrence by between 70% and 80%, compared with 50% for tamoxifen (Ackerman, Houston Chronicle, 12/9).
Participants who took Arimidex also experienced fewer serious side effects than those who took tamoxifen, which can increase the risk for blood clots, strokes and uterine cancer. However, Arimidex did not decrease the risk for osteoporosis, as tamoxifen does (Washington Post, 12/9). Researchers could not determine whether participants who took Arimidex experienced significant improvement in overall survival rates based on the study, but 13% fewer cancer deaths occurred among those who took Arimidex (Ackerman, Houston Chronicle, 12/9).
The authors of the study said the results indicate that aromatase inhibitors should replace tamoxifen as the primary treatment for older women with breast cancer, but some experts said that "it remains unclear whether all eligible women should immediately start with an aromatase inhibitor" before they take tamoxifen, the Post reports. Anthony Howell, lead author of the study and a professor of medicine at the University of Manchester in Britain, said, "We think women should start right away with an aromatase inhibitor. ... We think the benefit justifies offering this treatment as early as possible" (Washington Post, 12/9). Howell added, "I think tamoxifen is going to have a difficult time from now on" (New York Times, 12/9).
Aman Buzdar, a professor at the University of Texas M.D. Anderson Cancer Center and lead author of the study, said, "I hope with this new data doctors start using Arimidex as their new first choice. It's the better drug" (Houston Chronicle, 12/9). However, researchers will not complete studies to compare the effectiveness of aromatase inhibitors alone with a combination of the two treatments (New York Times, 12/9). Researchers also said that the long-term effects of aromatase inhibitors remain undetermined (Szabo, USA Today, 12/9).
Eric Winer, chair of the technology assessment committee for the American Society of Clinical Oncology, which last month recommended that breast cancer patients should take aromatase inhibitors as part of their treatment, said, "The unanswered question at the moment is whether aromatase inhibitors should be used as an initial therapy or whether they might work even better if tamoxifen is given first for some amount of time" (New York Times, 12/9). Winer added, "With tamoxifen, it took us well over a decade before we understood all the side effects. We have to be really careful that we don't rush to judgment" (USA Today, 12/9). In addition, Winer said that aromatase inhibitors can cost several times as much as tamoxifen. "These are important drugs. They add to what tamoxifen can do. It's a relatively small price to pay if there are substantial benefits," he said (Bavley, Kansas City Star, 12/9).
CBS' "Evening News" on Wednesday reported on the study. The segment includes comments Buzdar and Dr. Larry Norton of the Memorial Sloan-Kettering Cancer Center (Alfonsi, "Evening News," CBS, 12/8). The complete segment is available online in RealPlayer.
A second study presented at the meeting on Wednesday included almost 5,000 breast cancer patients and found that participants who switched to Aromasin, an aromatase inhibitor manufactured by Pfizer, after two years of treatment with tamoxifen experienced "substantially more effective" results than those who took tamoxifen for five years, the Los Angeles Times reports. The study found that participants who switched to Aromasin had a 30% reduction in breast cancer recurrence over three years and a 54% decrease in the development of a tumor in the other breast. A third study, which involved more than 3,000 breast cancer patients, found that participants who switched from tamoxifen to Arimidex after two or three years reduced their risk of recurrence by 40% (Los Angeles Times, 12/9).
In addition, a pilot study that involved about two dozen breast cancer patients who have taken Femara, an aromatase inhibitor manufactured by Novartis, for six months has found that 16 of the participants have experienced a reduction in abnormal cell growth (Kansas City Star, 12/9). Charles Coombes, who worked on the Aromasin study, said that the results indicate the benefits of aromatase inhibitors "justifies offering treatment as early as possible." (Los Angeles Times, 12/9). Coombes added, "The idea of switching treatment, I believe, is here to stay" (Marchione, AP/Contra Costa Times, 12/9).
In related news, M.D. Anderson researchers at the meeting on Wednesday presented a study that found a form of gene therapy reduced breast cancer tumor size by an average of about 80% prior to surgery. Researchers injected the therapy, called Advexin, into the tumor site of 12 breast cancer patients with inoperable Stage 3B cancer. The patients also received chemotherapy. Advexin allowed many participants to have lumpectomies rather than mastectomies and decreased the size of tumors in the lymph nodes, the study found (Houston Chronicle, 12/9).This is part of the California Healthline Daily Edition, a summary of health policy coverage from major news organizations. Sign up for an email subscription.