Clinical correlations with chemosensitivities measured in a rapid thymidine incorporation assay

A rapid assay for in vitro chemosensitivity testing measuring [3H]thymidine incorporation has been developed. Results of this assay correlate highly with chemosensitivities determined by the soft-agar clonogenic assay. A correlative study was carried out on 219 solid tumor specimens to assess the ability of the rapid assay to predict clinical response to antineoplastic therapy. One hundred forty-two of 219 tumors (65%) yielded chemosensitivity data. Of these, 33 were evaluable for in vitro-in vivo correlations. In vitro sensitivity (greater than or equal to 80% inhibition of thymidine uptake) was associated with clinical response in 6 of 13 patients. In vitro resistance was associated with progressive disease in 20 of 20 patients. The rapid assay offers several advantages over the soft-agar clonogenic assay, including higher success rate, avoidance of clumping artifact, shorter time course (5 days), and very low false-negative rate. Further refinement may be necessary, but the rapid assay appears to have potential for individualizing solid tumor chemotherapy.