Dose-effect relationship for palliative radiotherapy of bone metastases

Ninety-three patients with a total of 181 symptomatic bone metastases treated for palliation between 1994 and 1996 have been retrospectively analysed. The basic policy was to use the conventional 2-3 Gy per day, 5 days per week, for a total of 30-50 Gy. For patients with poor conditions, a single fraction of 4 Gy or 8 Gy, or two fractions of 4 Gy was used. Improvement rates of pain score according to total dose groups were; 77% (34/44) for 4-8 Gy, 77% (24/31) for 9-28 Gy, 82% (44/54) for 30-39.6 Gy, 98% (51/52) for 40-60 Gy. The improvement rate was significantly better with a total dose of 40-60 Gy than with a total dose of 30-39.6 Gy. The complete response rates of pain score were 46% (20/44) for 4-8 Gy, 52% (16/31) for 9-28 Gy, 45% (24/54) for 30-39.6 Gy, 75% (39/52) for 40-60 Gy. The complete response rate was significantly better with a total dose of 40-60 Gy than a total dose of 30-39.6 Gy. Improvement curves for the scores were made to compare the time profile of pain relief by total dose groups. According to the improvement curves, all of the groups exhibited virtually identical effects concerning pain relief. The improvement rate of pain score with a total dose of 4-28 Gy was as good as the score with a total dose of more than 30 Gy, possibly because analgesics were continued. The complete response rates of pain score and narcotic score at 8 weeks were 40% (36/89) for 4-39.6 Gy and 67% (35/52) for 40-60 Gy. Frequency of acute side effects necessary for medication was 25% with a total dose of 30-60 Gy and 6% with a total dose of 4-28 Gy. The recurrence rates tended to decrease with increase in total dose, but the difference was not significant. These differences were significant. The palliative effect of 8 Gy in a single fraction or 4 Gy in two fractions is sufficient enough for patients with poor prognosis. A dose of 40 Gy or more is indicated for patients with good prognosis of more than 6 months. (K.H.)