In the new study, the research team investigated whether the variation affected survival in two separate groups of women with breast cancer: 248 women in the United States and 340 women in Norway. Some of the women received chemotherapy, and some did not receive chemotherapy. The team first analyzed DNA from the women to determine their genotype, meaning which types of the SOD2 gene they had. The researchers found that, among patients who received chemotherapy, those who had one form had decreased survival and those with another form had the poorest survival. In contrast, the genotype of SOD2 did not affect survival among those who did not receive chemotherapy.

Next, the team looked at the relationship between SOD2 genotype and the type of chemotherapy the women received. The data were analyzed according to which of three types of commonly used chemotherapy drugs were administered: doxorubicin, 5-fluorouracil, or cyclophosphamide. Both doxorubicin and cyclophosphamide generate reactive oxygen species in cancer cells during treatment. The researchers determined that the presence of a particular variant was associated with decreased survival of patients treated with chemotherapy regimens that contained any of the three drugs. However, the most significant effects were found with the drug cyclophosphamide. Women with a distinct variant form of SOD2 and who received cyclophosphamide-containing chemotherapy had the poorest survival.

The research team says more work is necessary to confirm these findings and to examine the precise mechanism by which a genotype influences the response of cancer cells to cyclophosphamide. The team plans to examine the influence of several variations on the resistance to other chemotherapies.

For more information on Dr. Ambs' research, please go to ccrncer/staff/staff.asp?profileid=6100.

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