In vitro assessment of antineoplastic therapy. New indication for thoracotomy?

Selection and determination of the efficacy of antineoplastic agents has been dependent upon the trial and error method of observing measurable disease. Such methods subject the patient not only to loss of precious time but to needless toxicity if the drug is ineffective. The clonogenic assay, an in vitro assessment of tumor cell sensitivity to antineoplastic agents, has the potential for individualizing therapy. In this assay, tumor cells exposed to various drugs are cloned in soft agar. In the 16 primary and 24 metastatic pulmonary tumors tested with this technique, a growth rate of 80% was achieved. Fifty-five percent of the primary tumors and 60% of the metastatic lesions responded in vitro to one or more of the test drugs. There were twelve possible correlations between in vitro and in vivo results. In four of 12 assays, in vivo sensitivity was predicted and three of four patients demonstrated a clinical response. No drug that was inactive in vitro had activity in vivo. Prior knowledge of in vitro sensitivity may dictate a more aggressive surgical approach to pulmonary metastatic disease, whereas in vitro resistance would call for more conservative treatment. Just as with estrogen receptor status in breast cancer, data derived from the clonogenic assay may ultimately be of such import that thoracotomy would be warranted solely for the purpose of obtaining tissue for the assay.