Rise in leukemia linked to breast cancer chemo. (Five-Year Cumulative Incidence of 1.1%).

SAN ANTONIO -- The incidence of secondary acute myeloid leukemia and myelodysplastic syndrome is dramatically increased following dose-intensified regimens of doxorubicin and cyclophosphamide for breast cancer, Dr. Roy E. Smith reported.

The rate of acute myeloid leukemia/myelodysplastic syndrome (AML/MDS) also appears to be elevated in women who have undergone lumpectomy with in-breast radiation therapy compared with mastectomy with no radiation therapy This is an "alarming" new finding that requires further confirmation, he said at the annual breast cancer symposium sponsored by the San Antonio Cancer Institute.

National Cancer Institute officials are deeply concerned about recent reports of secondary AML/MDS in cancer patients who have undergone chemotherapy said Dr. Smith, a medical oncologist at the National Surgical Adjuvant Breast and Bowel Project operations center in Pittsburgh.

They asked NSABP organizers to examine their clinical trials database and report whether they found such an association. Dr. Smith reported on 8,563 women with breast cancer who participated in six now-closed NSABP trials of adjuvant chemotherapy using six distinct doxorubicin / cyclophosphamide dosing regimens. Median follow-up time was 122 months.

During the 61,810 patient-years of follow-up, 22 women developed AML and 21 developed MDS, of whom 7 progressed to AML. This works out to an overall 5-year cumulative incidence of AML/MDS of 1.1%. The median latency period was 38 months.

The incidence of AML / MDS associated with the more intensive doxorubicin / cyclophosphamide regimens was up to 6.16-fold greater than with standard doxorubicin cyclophosphamide. Moreover, rates of these blood dyscrasias were 20-53 times higher in the ...