Serial Labeling Index Determination as a Predictor of Response in Human Solid Tumors

A rapid method for determining labeling indices in solid tumor specimens, tumor-induced effusions, and tumor-bearing bone marrows was utilized in 116 patients. Of these, 48 patients were studied pre- and postchemotherapy. The magnitude of a significant change in labeling index (LI%) was determined statistically. Of the 48 patients studied serially, 42 were studied 17 days or less following completion of their chemotherapy. In 26 patients without a significant change in tumor LI%, there was no subsequent clinical response to chemotherapy. Three additional patients in this group are inevaluable at present. In 11 patients, there was a significant fall in tumor LI% following chemotherapy. Seven of these had a 50% or greater regression of demonstrable disease, one patient had definite tumor effect but the effect was not a partial response and three patients were not evaluable for clinical response. In two patients there was a significant increase in tumor LI% and the patients had rapid tumor progression and death. Predictions derived from serial study of the LI% by this method correlate significantly with subsequent behavior of the tumors tested following chemotherapy and may prove clinically useful in making decisions about when or whether to change therapy.