Growth rates of small cell bronchogenic carcinomas.

In reviewing a series of 144 patients with small cell bronchogenic carcinoma, 12 were found to have serially measurable roentgenographic lesions prior to therapy. Although caliper-based measurements and a silhouette cutout method gave comparable sets of tumor doubling time data, inter-observer variability was less with the silhouette cutout method. Tumor doubling times in small cell bronchogenic carcinoma ranged between 25 and 160 days, with a median of 77 days, a log mean of 81 days, and an arithmetic mean of 91 days. There was no apparent relation between tumor doubling time and tumor location, histologic subtype, response to therapy, or patient survival. The data indicate that small cell bronchogenic carcinoma of the lung is a relatively slowly growing tumor. Assuming that late subclinical disease exhibits growth characteristics that are similar to those seen in the clinical stages of growth, it can be estimated that residual body tumor burdens of 1 X 10(6) cells may be followed by tumor recurrence times of 2 years or longer; the likelihood of "cure" should not be entertained in patients with disease-free intervals shorter than 4-5 years.