LOSS OF HETEROZYGOSITY AT 7Q31 IN BREAST-CANCER - RESULTS FROM AN INTERNATIONAL COLLABORATIVE STUDY-GROUP

Loss of heterozygosity (LOH) at 7q31 has been claimed to occur in over 80% of all breast cancers and to be of prognostic significance. This would make this genetic alteration the most common event observed in b reast cancer to date. Others, however, have been unable to confirm thi s high incidence. In this multicenter study, we have compiled LOH scor ings for three polymorphic markers for 7q31-q32 in 683 breast tumors. Although some significant differences between centers existed, no cent er reported more than 40% LOH, and the average rate was 19%. Disease-f ree and overall survival of the patients whose tumors carried LOH at 7 q31 did not differ significantly from those patients whose tumors show ed retention of heterozygosity at 7q31. In a double-blind scoring of a subset of the raw data, an average discordant rate of LOH scoring of 12% was observed. While startling in itself, this was unable to explai n the variation among centers, nor the difference with the initially r eported high rate of LOH. We conclude that LOH at 7q31 is not importan t as a genetic alteration in breast cancer as originally suggested, no r a strong determinant of disease outcome. (C) 1997 Wiley-Liss, Inc.