There may be different time-dose schedules which will favor different tumors in addition to differences between normal tissues and neoplasms that could lead to more favorable therapeutic ratio. In seeking optimum fractionation schedules, it is equally important to understand normal tissue reactions as tumor reactions. In our previous experiments, the best cure rate of spontaneous mammary cancer in C3H mice was obtained by 2 fractions per week. Thus to the patients irradiation was performed twice a week with 600 rad per fraction for 2 to 4 consecutive weeks.
From January 1970 to December 1974, 67 separate courses of electron beam therapy were given to 35 out of 219 patients referred to the radiology department with breast cancer. These 35 patients were presented with chest wall recurrence of primary carcinoma of the breast which was initially treated by surgery. Prophylactic radiation was given to the chest wall in 26 patients after mastectomy.
The results of electron beam therapy were summarized as follow :
1. In 59 out of 67 treated lesions, the tumors were disappeared completely and only in 2, the lesion was unchanged. In remainder, the tumor was diminished in size.
2. The chest wall recurrence was designated as “disseminated type” and “localized type”. In the former type, the tumor was disappeared in 100%, whereas the latter only in 50%. If the tumor exceeds 4cm in diameter, the effect of radiation was especially poor.
3. As for the radiation effect on various histological types of the “localized type” tumor, papillotubular carcinoma was completely disappeared in all 3 lesions, whereas scirrhous carcinoma was not completely disappeared at any of the 5 lesions. Medullary tubular carcinoma was completely disappeared in 5 of 8 lesions, resulting in intermediate radiation effect between papillotubular and medullary tubular carcinoma.
4. Chest wall recurrence among lesions given prophylactic radiation therapy following mastectomy was obserbed in 4 patients. In spite of unfavorable tumor bed for radiation therapy in these 4 patients, all the tumor were completely disappeared by the electron beam therapy.
5. Age and local control ratio : In age group 40-59 year-old, the tumor was disappeared in 98%, 73% in 20-39 and 69% in 60-79 age group.
6. Erosion of the skin as the side effect observed in 60% of all treated lesions. In the patients who were irradiated with 4, 5, 6, 7 or more fractions, skin erosion was observed in 12%, 56%, 72% and 100% respectively. The larger the size of field irradiated, the higher the incidence of erosion.
7. Radiation pneumopathy was present in 15%. The incidence in this series was lower than the one treated with
60Co γ-rays and conventional X-rays. The use of an adequate absorber could further decrease the incidence of pneumopathy.
8. In this method, the total dose of 3000 rad seems to be sufficient as a cancerocidal dose for the “disseminated type”. For some of the “localized type” surgical treatment might be suitable.
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