In vitro prediction of cytostatic drug resistance in primary cell cultures of solid malignant tumours.

The in vitro monolayer proliferation assay (MP-assay) described here enables predictive determination of the efficacy of anticancer drugs considered for clinical application. The assay was designed (1) to achieve a high plating efficiency, (2) to adapt in vitro growth as close as possible to in vivo conditions, and (3) to prove that the cells in vitro correspond with the in vivo tumour cells they were derived from. From 452 freshly explanted or biopsied tumours, 321 (71%) proliferating cultures could be established. To prove malignant origin of the incubated cells each strain was characterised by DNA-cytophotometry for aneuploidy and by immunocytochemistry for marker proteins. Drug potency was determined by comparing the number of living cells in drug-treated cultures with non-treated controls. Drug concentrations in vitro corresponded with those achievable in tumour tissue and thus represented clinically relevant levels. Growth inhibition in vitro was correlated with in vivo tumour response. Two hundred in vitro/in vivo correlations were performed (50 retrospective, 150 prospective). Overall predictive accuracy of the MP-assay was 86%, with correct indication of resistance in 94.5% and of sensitivity in 75.8% (P < 0.001). The results show that the proposed assay is capable of estimating the response probability of cytostatic drugs in individual tumours and thus can contribute to reducing the applications of non-effective drugs and, within limitations, to improving the basis of drug selection.

[Individualization of chemotherapy through in vitro predictive determination of the cytostatic sensitivity of malignant tumors]. / Individualisierung der Chemotherapie durch prädiktive In-vitro-Bestimmung der Zytostatikasensitivität maligner Tumoren.

An in-vitro test was developed for predicting the efficacy of anti-tumour chemotherapy. Cell cultures were grown from freshly removed tumours and it was then demonstrated by DNA cytophotometry and immuno-cyto-chemistry whether the growing tumour cells corresponded to those of the original tumour cells. Several cytostatic agents were then tested for their efficacy of inhibiting growth at clinically customary dosage. Growing cell cultures were established in 306 of 413 submitted tumours (74%). They responded quite differently to the various drugs that were tried. The clinical course in 94 cases was observed for minimally four and a mean of eight months to obtain an in-vitro to in-vivo correlation of response, with 178 individual correlations. A discrepancy was recorded in 16% of cases, a false-positive in-vitro sensitivity result was 3.6 times more frequently associated with an in vivo resistance than the reverse. Concordance between test results and clinical tumour response occurred in 84%. The monolayer proliferation assay correctly indicated resistance in 93.8%, sensitivity in 72.8%.