Preoperative Irradiation: Evaluation by a Simple Experimental Model

Publisher Website
Google Scholar
Abstract
In recent years, a number of workers have considered the role of preoperative or postoperative irradiation and/or chemotherapy in the control of metastases or local implantation after surgery for cancer in man (3, 4, 6, 17). Since large doses of radiation may delay surgery, impair the healing process, or otherwise compromise the surgical field, there is interest in the effectiveness of small doses in conjunction with surgery. Clinical success with less than cancerocidal doses has been reported (2, 15, 18, 19), but a considerable divergence of clinical opinion exists as to their real value. Other considerations, also, such as the optimum time span between the completion of irradiation and the institution of surgery, are in question. Employment of transplantable tumors in experimental animals to simulate the conditions at surgery is no substitute for clinical observation, but may readily provide corroboration and extension of such observations. Small doses of radiation to tumors prior to transplantation have been shown to decrease the number of successful transplants in the new hosts (5, 7, 11). Preoperative irradiation has decreased the number of tumor recurrences after transplanted tumors have been surgically removed (1, 12). We have demonstrated that the transfer of a transplantable mouse tumor from donor to recipient can be easily and efficiently accomplished by drawing a curved surgical needle once through the donor tumor and then once through the recipient's thigh (7). This method was used as an experimental model approaching the conditions at surgery. The experiments reported here were designed to investigate the effectiveness of less than cancerocidal doses of preoperative irradiation in the tumor-host system and to evaluate the influence of increasing time lapse between irradiation and transplantation on tumor development in the new hosts. Materials and Methods Tumor: A transplantable rhabdomyo-sarcoma which originated in and has been carried in C3H mice was used in these experiments. This tumor was obtained through the courtesy of Dr. V. Suntzeff, at Washington University, St. Louis (9). Hosts: In this laboratory (VA Hospital, Long Beach, Calif.) all transplants were made into young male C3H mice, ranging in age from one and a half to three months, obtained from the Roscoe B. Jackson Laboratory (Bar Harbor, Maine). All the animals, in groups of 10, were putinto metal cages with food (Wayne Lab Blox) and water ad libitum. Method of Tumor Transfer: Tumors were transplanted exclusively by means of a curved surgical needle, employing our previously reported method. Unless otherwise stated in the individual experiments, the donor tumors were two and a half to three weeks old and ranged in size from 1 to 1.5 cm. in diameter at the time of transfer. (Age and size ranges were the same for both transplantation and irradiation.) The donor mouse was anesthetized with Nembutal and immobilized on a cork board.