Factors that influence growth of head and neck squamous carcinoma in the soft agar cloning assay.

A soft agar cloning assay was used to culture 158 specimens of head and neck tumors. Fifty-seven (36%) tumors were successfully cloned, 56 (35%) specimens failed to grow, and 45 (29%) were contaminated. There was no correlation of growth or cloning efficiency with the age of the patient, stage of the disease, degree of histologic differentiation, previous exposure to radiation therapy or chemotherapy, or subsequent survival. Sufficient cells were available to perform one to six (median, 2) chemosensitivity tests (total of 81) on specimens from 31 patients. Using 30% or less in vitro survival as the criterion for chemosensitivity, four patients were sensitive to one or more drugs. Only one of these patients received the same drug tested in vitro, and this tumor proved to be resistant. The cloning assay has not yet proved useful in predicting chemosensitivity in individual patients because of technical difficulties (low percentage of successful growth and high contamination rates).