Prognostic potential of DNA flow cytometry measurements in node-negative breast cancer patients: preliminary analysis of an intergroup study (INT 0076).

ABSTRACT

An ancillary study (INT 0076) to the Intergroup clinical trial of node-negative breast cancer patients (INT 0011) was performed to retrospectively evaluate DNA flow cytometry measurements of ploidy (DNA content) and proliferative capacity (S-phase fraction) for their ability to predict time to recurrence. Of the 915 patients eligible for the clinical trial, 788 were registered for the ancillary flow cytometry study (INT 0076). Four hundred and three of these patients [estrogen receptor (ER)-positive, tumor size less than 3 cm] had been registered to the observation arm of the clinical trial and 385 (ER-negative and/or tumor size greater than or equal to 3 cm) had been randomly assigned to adjuvant chemotherapy (cyclophosphamide, methotrexate, fluorouracil, and prednisone for six cycles) or to observation. Paraffin blocks from 95% (748 of 788) of these patients were obtained, 712 of which had sufficient cancer tissue to be evaluable for the flow cytometric assay. DNA ploidy status (DNA diploid vs DNA aneuploid) was evaluable for 565 (79%) specimens, 64% of which were aneuploid. Proliferative capacity was estimated by the percentage of cells having an S-phase DNA content, using a trapezoidal modeling algorithm(s) as previously described. The median S-phase value for the entire group (both registered and randomly assigned patients) was 6.97%, which defined the cutoff for interpretation of high or low S-phase values. With a median follow-up time of 4.55 years, S-phase fraction, but not ploidy status, is a significant predictor for time to recurrence in both the randomly assigned and the untreated population (observed registered group and observed randomly assigned group).(ABSTRACT TRUNCATED AT 250 WORDS)