The 1998 publication of the NSABP P-1 prevention trial led to considerable discussion in the breast cancer research community about the need to routinely employ quantitative risk assessment in women over the age of 35. The P-1 study utilized the Gail model and established a 1.67% five-year breast cancer risk as a key entry criterion. This is also being incorporated into the current NSAPB prevention trial, protocol P-2, comparing tamoxifen to raloxifene. The MBCC patterns of care study demonstrated that 76% of surgeons are currently utilizing the Gail model to assess breast cancer risk in their patients; however, only 25% of these physicians have initiated tamoxifen for chemoprevention in any patient in the past year. The number of physicians prescribing tamoxifen chemoprevention increases dramatically in physicians attending the Miami Breast Cancer Conference.

Fisher B et al. Tamoxifen for prevention of breast cancer: Report of the National Surgical Adjuvant Breast and Bowel Project P-1 Study. J Natl Cancer Inst 1998;90(18):1371-88. Abstract

Port ER et al. Patient reluctance toward tamoxifen use for breast cancer primary prevention. Ann Surg Oncol 2001;8(7):580-5. Abstract

Rockhill B et al. Validation of the Gail et al. model of breast cancer risk prediction and implications for chemoprevention. J Natl Cancer Inst 2001;93(5):358-66. Abstract

Vogel VG. Follow-up of the breast cancer prevention trial and the future of breast cancer prevention efforts. Clin Cancer Res 2001;7(Suppl 12):4413s-18s. Abstract

Implications of the ATAC Trial in Chemoprevention

Surgeons: What results would you expect from a randomized clinical trial comparing tamoxifen to anastrozole in high-risk postmenopausal women? Surgeons: Based on the ATAC data, would you currently use anastrozole or another aromatase inhibitor in a high-risk postmenopausal woman?

The primary rationale for utilizing tamoxifen in high-risk women in clinical trials, such as NSABP P-1, was the reduction in contralateral breast cancer observed with adjuvant tamoxifen in patients with invasive breast cancer. The preliminary results of the ATAC trial demonstrated 56% fewer second breast cancers in women randomized to anastrozole compared to tamoxifen. Based on these early findings, most surgeons surveyed believe that a randomized trial comparing anastrozole to tamoxifen in high-risk postmenopausal women would demonstrate both greater efficacy and less toxicity for anastrozole. Sixty percent of surgeons would use anastrozole in these women at the present time, for which there is no FDA indication, but breast cancer researchers almost uniformly believe that aromatase inhibitors should only be utilized in high-risk patients as part of a clinical trial. In the United Kingdom, a massive trial is being planned to evaluate the use of anastrozole in high-risk patients. The final design of this IBIS II trial is awaiting the presentation of IBIS I study results comparing tamoxifen to placebo.

Dowsett M. Theoretical considerations for the ideal aromatase inhibitor. Breast Cancer Res Treat 1998;49 Suppl 1:S39-44. Abstract

Goss PE, Strasser K. Aromatase inhibitors in the treatment and prevention of breast cancer. J Clin Oncol 2001;19(3):881-94. Abstract

Lonning PE et al. The potential for aromatase inhibition in breast cancer prevention. Clin Cancer Res 2001;7(12 Suppl):4423s-4428s. Abstract

Santen RJ, Harvey HA. Use of aromatase inhibitors in breast carcinoma. Endocr Relat Cancer 1999;6(1):75-92. Abstract

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