Measurements of cellular proliferation by H-3-thymidine-labeling index and flow cytometry in breast cancer patients

: In 50 node negative breast cancer patients, tumor S-phase fraction (SPF) was determined by H-3-thymidine labeling index ((HTLI)-H-3) or flow cytometry (FC). Forty-five patients had tumor cell kinetics measured by both techniques. Twenty-three patients were classified as having high proliferative activity and 22 low by (HTLI)-H-3, while 32 as highly proliferating and 13 low proliferating by FC. In 30 patients only, both indices agreed on identifying high or low proliferative activity. These results suggest the need of more careful attention to standardization and quality control of cell kinetic data before carrying out clinical trials based on these parameters.