Sustained-release implants of chemical carcinogens in the canine tracheobronchial tree.

A proved carcinogen, benzo[a]pyrene (BP), was incorporated into liquid silicone rubber polymer which was then vulcanized into solid form. Discs of BP polymer containing 9.05 to 12.12% BP were sutured into the trachea and right main bronchi of 10 dogs which were observed for 3 to 8 months. The discs were either in contact with the endobronchial surface of the mucosa or placed into submucosal pockets. All discs that were implanted submucosally remain in place. Only 2 discs implanted by the fixation method were extruded. The pocket implants of BP polymer caused ulceration and erosion of the mucosa; these changes did not occur from discs of polymer without carcinogen. To date these implants have induced squamous metaplasia with atypical changes. A method for sustained-release implantation of carcinogens in the canine tracheobronchial tree has been developed.