Cloning efficiency. A possible prognostic indicator in squamous cell carcinoma of the head and neck.

Seventy-three squamous cell carcinomas arising in the head and neck region were cultured using the soft agar clonogenic system. Thirty-six (49%) demonstrated clonal growth. The cloning efficiency was variable, ranging from 0.001% to 1.67% (median, 0.004%). Statistically significant correlations of high cloning efficiency with advanced local class, increased stage, and decreased survival were observed. There was no correlation between cloning efficiency and T-class or modified Jakobsson's histologic grade. A cloning efficiency of greater than or equal to 0.005% was associated with a high likelihood of death from disease or the development of recurrent disease. For head and neck squamous cell carcinomas, the cloning efficiency in soft agar appears to be a potentially useful prognostic indicator.