Treatment of Carcinoma of the Prostate by Cobalt-Beam Therapy

The following paper describes only 11 patients treated over the last seven years. Because the number is so small originally no thought was given to presenting the results except within our own group of radiotherapists. However, with the exception of the series presented by Bagshaw et al. (1), in which 73 patients were discussed, 30 of whom were followed for over five years, no recent paper describing treatment by external irradiation has dealt with more than a small number of patients. George et al. (2) dealt in a preliminary report with 9 and del Regato (3) with 7. As del Regato remarked, the numbers are small, but the effects of external irradiation need emphasizing by as many different centers as possible in the hope that more use may be made of this mode of therapy. Each center appears to have a different physical approach. Bagshaw used a small target size and rotation with a linear accelerator; George used cobalt-beam therapy with two relatively large opposed fields; and del Regato employed three contributing large fields with cobalt-beam therapy. The method presented here was based on our standard bladder technic and involved fields large enough wholly to enclose the primary tumor with an appropriate margin—the average size being 6 × 6 cm. The prostate was localized radiographically by the use of a circular metal marker, 3 cm in diameter, placed on the skin over the approximate area of the bladder neck. Radiopaque material was introduced into the bladder, and a roentgenogram was taken with the patient in the supine position. A similar film was taken with the patient in the prone position. In each position, lateral films were also obtained. The metal marker had a central hole through which a drop of india ink was put on the skin surface. Pricking with a sterile needle here produced a permanent but tiny tattoo. From the prone and supine films, the central point immediately over the prostate area was determined and related to the center of the metal disk, allowance being made for the magnification on the film. This center was then related to the skin tattoo and transferred to the skin by carbolfuchsin paint. From the lateral films the depth of the center of the tumor from the skin was found. These measurements enabled the treatment to be given through four angled fields∕at 45° to the central mark, using the pin and arc. Table I gives a detailed analysis of each patient's case and the time∕dose relationship. Only a few comments need be added. Nine of the first 10 patients came from a single urologist. Patients are treated by us only after referral from their own doctor∕we are not a cancer clinic. Of the 10 patients, 3 have been alive and well for periods of nearly five to nearly seven years with no metastases. One is alive with multiple metastases.