Comparison of conventional and supervoltage radiation in the management of cancer of the cervix. Analysis of survival rates and complications.

Abstract

The earliest form of radiation therapy for carcinoma of the cervix uteri consisted of intracavitary radium alone. Although permanent cures were obtained, it soon became apparent that the addition of external irradiation to increase the dose delivered to the pelvic walls resulted in an appreciable increase in the survival rate for moderately advanced neoplasms (Stages II and III). With the availability of supervoltage radiation, the trend has been toward greater reliance on the use of external radiation for the treatment of the moderately advanced cases. The most commonly used technic at present is whole-pelvis irradiation combined with intracavitary radium to increase the dose delivered to the central portion of the tumor. Comparison of cure rates in series treated before and after the availability of supervoltage radiation has shown a further increase in the survival rate for Stage II and Stage III carcinomas. This improvement seems to be due to the high-dose homogeneous radiation of the pelvis; it is therefore felt that supervoltage radiation is superior to orthovoltage radiation in the treatment of this group of tumors. The aim of this study is to compare the effectiveness of orthovoltage and supervoltage radiation in the management of moderately advanced carcinoma of the cervix. All cases of carcinoma of the cervix uteri treated at the Ellis Fischel Cancer Hospital over a ten-year period were analyzed (Table I). During the first half of this period, 300 patients received definitive treatment consisting of external orthovoltage radiation and intracavitary radium. During the second half of the period, another group of 300 patients was treated in a similar fashion, except that external radiation was given by Cobalt-60 teletherapy. These two groups of patients are comparable except for a significant increase in the number of patients with Stage II cancer and concomitant decrease in the number of patients with Stage IV cancer. Throughout the ten-year period, Stage I cancers were treated primarily with intracavitary radiation. External irradiation was used only to increase the dose in the parametrial areas or to reduce the tumor mass in some bulky tumors prior to intracavitary irradiation. In this group of patients, we do not feel that the particular form of external radiation used would appreciably affect the survival rates. Orthovoltage radiation was delivered with a 250 kV apparatus with a half-value layer of 3 mm copper. A target-skin distance of 80 cm was used in order to increase the depth dose obtained. Two adjacent anterior fields and two adjacent posterior fields were used, each field receiving a dose of 3000 R in air. In addition, two sacrosciatic fields were used, each one receiving a dose of 2000 R in air. In an average-sized patient the dose received in the pelvis ranged from approximately 4000 R at the level of the cervix to 3000 R in the pelvic wall.