Colony formation in vitro as a prognostic indicator for primary breast cancer.

Cells from some, but not all, tumor biopsy samples form colonies when cultured in semi-solid media. The possibility that colony formation by progenitor cells in these tumors may reflect a more "aggressive" phenotype bearing clinical implications was examined in a series of 61 patients with primary breast cancer. Tumor cells from 32 samples formed colonies in vitro. There was no correlation between colony formation and any of the standard clinical parameters such as tumor size, nodal status, metastatic spread, or hormone receptor levels. Eighteen patients had inflammatory, locally advanced and/or detectable metastatic breast cancer at the time of surgery. Sixteen of these patients have progressed and 15 have died, with no relationship between colony formation and survival. For the 43 remaining patients, 23 had a tissue sample that gave rise to colonies in vitro; 14 of these have relapsed, with a median relapse-free survival (RFS) of 37.6 months, and eight have died with a median survival time of 46.8 months. This is compared with four relapses (median RFS not reached, P = .0043, Peto-Pike), and four deaths (median not reached, P = .1175) in the group without growth of the tumor specimen. These results indicate that colony formation is an independent prognostic parameter for breast cancer, which may be useful for selecting patients who would benefit from more intensive therapy.