Biochemical measure of the volume doubling time of human pulmonary neoplasms

The volume doubling time (DT) of human lung neoplasms, determined from sequential, presurgery roentgenograms, was compared with biochemical and histologic observations on biopsy samples of the same tumors obtained during surgery. The DTs of the 16 neoplasms ranged from 24 days in an oat cell carcinoma to over 500 in a pulmonary carcinoid tumor, and showed a statistically significant, inverse correlation to the TK (thymidine kinase) and the UK (uridine kinase) concentration of the biopsy samples per g wet weight or mg DNA. Log DT bore a linear relationship to log TK (r = −0.75, P = 0.0008) and to log UK (r = −0.69, P = 0.0067), and an even better fit to the straight line was found when plotting the log of the standardized average of the two enzymes against log DT. The results demonstrate the feasibility of a biochemical method for determining the unknown DT of the many tumors that are not amenable (on account of shape, location, or lack of prior chest x‐rays) to the direct, radiologic determination of this useful, dynamic parameter of clinical malignancy.