'Viable' tumor cells in posttherapy biopsy specimens. A potential application of human tumor clonogenic cell culture.

Human carcinoma tissues were grown in culture for two to four weeks using the two-layer soft agar technique. All cultures that showed growth of tumor cell colonies also showed well-preserved, apparently healthy tumor cells lying singly. These cells showed neither proliferative capacity nor necrosis or morphologic degeneration during the time in soft agar. Thus, morphologic criteria seem to be poor indicators of tumor cell proliferative potential, at least in the short term. However, the method of soft agar tumor clonogenic cell culture itself provided a direct measure of tumor cell proliferative capacity, ie, the formation of colonies from single tumor cells. This may be valuable in directly assessing the presence of "viable" tumor cells in biopsy specimens taken after therapy, and thus guide further patient therapy.