Development of a rat lung cancer model.

A rat lung cancer model based on intrabronchial instillation of a tumor cell suspension has been developed for use in therapy and toxicity testing. Two tumors were used in this study, a sarcoma and an adenocarcinoma, both of which were of spontaneous origin in the strain of rats used. The inoculated tumor cells implant on the bronchiolar mucosa, forming a detectable single "primary" tumor resembling the spontaneous lung cancers arising in humans. The tumor growth is detectable by use of diagnostic radiographs, weight loss and other "clinical" signs. The tumors appear on chest radiographs 3 to 5 weeks after inoculation, and the implant rate is proportional to the number of tumor cells inoculated. Untreated animals have a median survival (after radiographic detection of the tumor) of 8 days, and die of local complications of tumor growth. When a slow growing transplantable tumor line of lung origin is developed, this model will be used to evaluate radiotherapy and chemotherapy schedules.