In vitro stem cell assay in head and neck squamous carcinoma.

Squamous cell carcinoma of the head and neck was successfully cultured from 33 to 73 specimens (45 percent) using the soft agar technique developed by Hamburger and Salmon. Successful cultures were evenly divided between biopsies of primary tumors and metastases; no growth and contaminated specimens predominantly came from biopsies of primary tumors. Prediction of viability before plating with trypan blue was unreliable. The cloning efficiencies in each histologic grade had a wide range, but the median cloning efficiency was higher for poorly differentiated tumors. Six of 11 patients with cloning efficiencies greater than 0.02 percent were dead of disease within 3 months, whereas only 1 of 16 patients with cloning efficiencies less than 0.02 percent was dead of disease at 3 months (p < 0.01). In vitro chemotherapeutic drug sensitivity testing correctly predicted in vivo resistance in three patients. The in vitro stem cell assay should prove a useful tool for clinical and biologic studies of head and neck cancer.