A comparison of two commercially available in vitro chemosensitivity assays

In vitro chemosensitivity assays (IVCAs) are expensive laboratory tests utilized to assist oncologists in the selection of chemotherapeutic regimens. Their utility is disputed; yet, these assays continue to be requested because of the importance of the information they can provide and their scientifically logical approach. Therefore, we compared the results of two assays offered to clinicians at our hospital; the extreme drug resistance assay performed by Oncotech (OT) and the fluorescent cytoprint assays performed by Analytical Biosystems (AB). The two techniques used and the expression of assay results by the two companies are discussed. Twenty neoplasms, all at least 3 cm in diameter and predominantly of breast and ovarian origin, were compared. OT performed 74 drug assays on 17 tumors, while AB performed 194 assays on the corresponding neoplasms; 3 neoplasms were insufficient for comparison. Evaluation of the results revealed apparent disagreement on at least 44 drug assays with complete disagreement on at least 2 of the drugs tested in 12 of 17 cases. In conclusion, based on available information, comparisons between IVCAs show great variation in results; prospective studies are needed to evaluate commercially available assays for correlation with clinical outcome, and results should be expressed so comparisons can be readily made. Though utility may be limited to tumors resistant to standard therapy, cost and benefit to the patient will ultimately determine the fate of these tests.