Growth rate patterns of solid tumors and their relation to responsiveness to therapy: an analytical review.

The clinical doubling times of human solid tumors are reviewed. Methods are also described for estimating subclinical tumor doubling times, and these methods are applied to Wilms' tumor, choriocarcinoma, Burkitt's tumor, and breast cancer. Rapidly growing tumors are often responsive to therapy, and such complete responses are often quite durable. Slowly growing tumors respond less favorably to therapy, and responses are generally not durable. Rapidly growing tumors in advanced stages are similar in their response behavior to the slowly growing tumors. A strategy based on cell kinetics principles and tumor doubling time data is proposed for improving therapeutic results in responsive tumors. Data on clinical and subclinical tumor doubling times are used to distinguish early recurrences from late recurrences in a given tumor type. Early recurrences call for intensification of induction therapy, whereas late recurrences call for prolongation of consolidative therapy. This strategy may also apply in adjuvant therapy of slowly growing tumors.