Palliative radiotherapy of a mouse mammary carcinoma

A mouse mammary carcinoma was exposed to one of three palliative treatment schemes: rapid, split, and extended. Tumors were treated at either 4 mm diameter or 8 mm diameter to compare the responses of small and large tumors to the three treatment schemes. In addition, acute skin reaction and late skin contracture were assessed. The results were: (1) The rapid treatment resulted in the greatest tumor response for 4 and 8 mm tumors but it also caused the most severe normal tissue reaction. (2) Lengthening the overall treatment time to 5 weeks (extended treatment) resulted in the poorest response for both large and small tumors. (3) The split course technique was almost as effective as the rapid course in treating small tumors, but its effectiveness was reduced if treatment was delayed until the tumor reached 8 mm in diameter. (4) The survival of mice with 4 mm tumors clearly depended upon the type of radiation schedule used, with the rapid treatment being superior. (5) If treatment was delayed until the tumors were large (8 mm diameter), there was no survival advantage between the three treatment schedules. (6) Palliation and survival were better when the tumor was treated when it was small, suggesting that palliation may be better if treatment is given early or electively.