The responsiveness of bone metastases to radiotherapy: the effect of site, histology and radiation dose on pain relief.

281 patients with a total of 463 symptomatic osseous metastases treated for palliation between 1975 and 1985 have been retrospectively analysed. The most frequent primary sites were breast (50.1%) prostate (16.6%) and lung (11%), accounting for more than three fourths of all metastatic areas. Other primaries were represented by bladder, kidney, colorectal, uterus (corpus and cervix) melanoma and thyroid tumors, and by cancer from unknown origin. Palliation was evaluated only on a subjective pain score. Complete response meant complete pain relief, and partial response meant more than 50% and less than complete pain relief in all treated sites. Complete response rates were similar independently from the primary site, except for the adenocarcinomas of the kidney and for non-small cell carcinomas of the lung in which the response tended to be lower. A correlation was also found between the incidence of pain relief and the site of bone metastases, in that a lower response was shown in limb localizations. Also, the number of metastatic sites did not influence the complete response rate. As expected, the response rate in all cases seemed to be dependent on total absorbed dose while, surprisingly, it could not be shown to be affected by the fraction size. A similar trend was shown for the pain recurrence.