Anastrozole for DCIS may lead to increased rate of disease-free survival

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Mammographer at WorkDuctal carcinoma in situ (DCIS) is the presence of abnormal cells inside a milk duct in the breast. DCIS is considered the earliest form of breast cancer, and is the most common type of non-invasive breast cancer. DCIS itself is not life-threatening, but having DCIS can increase the risk of developing an invasive breast cancer later on. Women who have breast-conserving surgery (lumpectomy) for DCIS without radiation therapy have about a 25 percent to 30 percent chance of having a recurrence at some point in the future. If radiation therapy is included in the treatment plan after surgery, the risk of recurrence drops to about 15 percent.

New research shows that for women diagnosed with DCIS, the aromatase inhibitor anastrozole (Arimidex) provided a statistically significant increased rate of disease-free survival compared with tamoxifen.

The research was presented last weekend at the American Society of Clinical Oncology (ASCO) annual meeting in Chicago. The study, led by Dr. Richard Margolese, MD, of the Jewish General Hospital at McGill University in Montreal, included more than 3,000 postmenopausal women who were randomly assigned to tamoxifen (20 mg/day) or anastrozole (1 mg/day). Each drug was given for five years. All participants had undergone lumpectomy and radiation therapy prior to starting hormone therapy.

The 10-year disease-free survival rate was 93.5 percent for those on anastrozole and 89.2 percent for those on tamoxifen. After an average follow-up period of 8.6 years, 114 breast cancers (including recurrences of DCIS and the development of a new breast cancer) were detected in the tamoxifen group compared to 84 cases in the anastrozole group. There were eight deaths due to breast cancer in the tamoxifen group compared to five in the anastrozole group.

However, a subgroup analysis revealed that the benefit of anastrozole was primarily in women younger than 60. In older women, 92.2 percent of those taking anastrozole experienced event-free survival compared to 90.2 percent of women taking tamoxifen. There is no good explanation for this, said Dr. Margolese.

"The good news is tamoxifen and anastrozole are both very effective, but it seems that women have better chances of staying well with anastrozole," Margolese said in an ASCO

press statement. "Women should also consider differences in side effects when discussing treatment options with their doctors."

ACSH advisor Dr. Clifford Hudis, MD, immediate past president of ASCO and Chief of the Breast Cancer Medicine Service at Memorial Sloan Kettering Cancer Center, told Medpage Today: "[C]linicians and patients are going to continue to struggle with whether they want to take systemic therapy for DCIS and...which toxicity profile they want to tolerate. The aromatase inhibitors are safer medically but they are difficult to take day by day. It's a bit of an irony that is not lost on people that the drug that is safer causes more day-to-day annoyance. We have to consider the tradeoffs when prescribing these medications."

He continued, "The good news is that people who want to do something have more options now, not fewer options, and that is good for everybody. The results in the DCIS setting are so favorable anyway that people will have to carefully consider if they want any therapy, and then which one."