The accumulation of multiple genetic abnormalities in individual tumor cells in human breast cancers: clinical prognostic implications.

PURPOSE: Human solid tumors undergo multiple genetic evolutionary changes as they evolve from the normal state to advanced stages of malignancy. This study characterizes the degree of advancement of primary human breast cancers in their genetic evolutionary pathways, and determines if this is of clinical significance. MATERIALS AND METHODS: Correlated cell-by-cell measurements of cell DNA content, HER-2/neu protein content per cell, and H-ras protein content per cell were obtained by means of multiparameter flow cytometry on primary tumors from 95 patients with clinically localized breast cancer. Laboratory findings were correlated with subsequent clinical course in 91 of these patients. RESULTS: Multiple genetic abnormalities were found to accumulate in individual cells in primary human breast cancers. Almost all tumors contained subsets of cells with one, two, or three abnormalities per cell in various combinations. After a median follow-up time of 32 months, 11 of 13 patients with early recurrence had primary tumors in which more than 5% of cells were hypertetraploid, overexpressed HER-2/neu protein, and overexpressed H-ras protein (triple-positive cells). The duration of disease-free survival among patients with primary tumors that contained triple-positive cells was significantly shorter than for patients whose tumors did not contain triple-positive cells. The presence of subpopulations of cells with maximums of only one abnormality per cell or only two abnormalities per cell, in any combination, was of no prognostic significance. Among patients whose nodal status was known, 12 had recurrent disease, and all had positive axillary nodes. Among 36 patients known to have negative axillary nodes, no recurrence has been reported to date. CONCLUSIONS: The number of genetic abnormalities that accumulate in individual cells in primary breast cancers reflects the degree of advancement of a tumor in its genetic evolutionary sequence, and provides useful clinical prognostic information. Because follow-up duration is still relatively short, and because disease in node-negative patients tends to recur later than in node-positive patients, it is still too early to know if three measurements per cell will be sufficient to improve prognosis in node-negative disease.