Linear Accelerator Supervoltage Radiotherapy

IN A COMPREHENSIVE survey, clinically evident carcinoma of the prostate was exceeded only by skin cancer as the most frequent malignant lesion in the male (1). In a review of available mortality statistics, Veenema et al. calculated that in 1962 prostatic cancer caused 14,000 deaths in the United States (2). In spite of this prevalence, primary treatment of this neoplasm by the radiotherapist has been curiously neglected. For example, the California study indicated that between 1942 and 1956 only 5 out of 2,492 cases of localized prostatic cancer were treated with irradiation.

It is perhaps paradoxical that, since the first aggressive surgical approach to carcinoma of the prostate by Young in 1904 (3) with radical perineal prostatectomy, the urologists have made creditable advances in the treatment of this disease with nonsurgical technics. The introduction of endocrine therapy by Huggins in 1941 and interstitial radiation therapy with radioactive gold by Flocks and his coworkers in 1951 are important examples (4–6). It was largely through the stimulation of one of our colleagues in urology, Dr. James Ownby, that we were encouraged to proceed with treatment by external radiation in a pilot study of suitable cases. Although several authors have reported five-year survival rates of between 50 and 89 per cent in highly selected patients treated by radical perineal prostatectomy and ten-year survival rates of between 25 and 37 per cent, Flocks and others have pointed out that approximately only 5 per cent of all patients are candidates for radical resection when first seen (7–14). An occasional patient in this small group may decline prostatectomy or castration because of the fear of impotence. An additional 55 per cent have disseminated metastases, while the remaining 40 per cent may be candidates for an attempt at local control of the disease by radiation therapy. The ability to control localized prostatic cancer by interstitial irradiation has been demonstrated by Flocks et al. (5, 6, 9–12). In this paper, an alternative method of administering external radiation to the prostate with a rotational technic is described. The Stanford medical linear accelerator (4.7 Mev) is used as the external radiation source (15).

Methods

Selection of Patients: Eighty-one patients were referred for definitive radiation therapy of primary carcinoma of the prostate. The age distribution of these patients and that described by Turner (14) are presented in Figure 1. Cases were selected for consideration of treatment on the basis of the following: (a) no demonstrable hematogenous metastases; (b) primary tumor localized to the region of the prostate, its capsule, or the immediately adjacent periprostatic tissue; (c) primary tumor considered by urologic consultation to be too large for radical prostatectomy.