Improvement of accuracy in radiotherapy for cancer of the head and neck using simplified shell

In this paper, we describe the comparative study as to the immobilization of the portal skin with or without shell. From May 1982 through December 1982, patients with carcinoma of the pharynx or larynx were selected to investigate the immobilization during the treatment. They were treated with parallel opposing portals of 4MV X-ray (NELAC-1004) in supine position. In the group of patients without shell, 4 early glottic cancer patients were selected for the pilot study and 30 treatment data were available for comparison with the movement during the treatment. In the group of patients with shell, 4 patients with early glottic cancer were consecutively selected for this study and 44 data of the intratreatment movement were obtained. As to the pharyngeal cancer patients, 61 controlled data were obtained from 9 patients and 177 data from 21 patients treated with the use of shell. This work clearly indicates that better immobilization is obtained in the patients treated with the employment of shell (p<<0.001). To investigate the reproducibility of the treatment portals, the data were obtained from 240 sheets of verification film taken for the 28 patients with head and neck cancer throughout the course of radiotherapy. All of these patients were treated with above described shell and fixing device. Mean values of the error of reproducibility are from 1.87mm to 2.81mm with the range of 95% confidence limits from 1.49mm to 2.25mm and from 1.86. to 3.75mm, respectively. (J.P.N.)