A Comparison of Radiation Therapy Outcomes of Bone Metastases Employing International Consensus Endpoints and Traditional Endpoints

Abstract

This study employs international consensus endpoints to evaluate the magnitude of pain relief achieved from palliative radiation therapy of bone metastases, and to compare and contrast these results with the traditionally reported rates. Patients with bone metastases referred for palliative radiation therapy were asked to rate their pain intensity on a categorical scale of 0–10 (0 = absence of pain; 10 = worst pain possible). Five hundred and eighteen patients were analyzed for the radiation therapy outcomes. Patient demographics and information on disease extent were collected. Analgesic intake during the preceding 24 hours was recorded and converted into total daily dose of oral morphine equivalent. For those who received radiation therapy, follow-up was conducted via telephone interviews at weeks 1, 2, 4, 8, and 12 after treatment to inquire about pain level and analgesic consumption. Pain score alone initially assessed radiation therapy outcome. Complete response (CR) was defined as a pain score of 0. Partial response (PR) was defined as a reduction of score ≥ 2 or ≥ 50% of the pretreatment pain score. We further analyzed outcomes using integrated pain and analgesic scores. Response was defined as either a reduction of pain score ≥ 2 with at least no increase in analgesics or a stable pain score with a ≥ 50% reduction in analgesic intake. The response rates were then reported employing international consensus endpoints. When response evaluation was by pain score alone, the PR rates at 1, 2, 4, 8, and 12 weeks were 41%, 41%, 39%, 35%, and 41%, respectively, and the CR rates were 21%, 30%, 32%, 35%, and 32%, respectively. When assessed by the integrated pain and analgesic scores, the response rates were 51%, 50%, 52%, 45%, and 48%, respectively. Using the international consensus endpoints, the PR rates at 1, 2, 4, 8, and 12 weeks were 32%, 28%, 26%, 22%, and 28%, respectively, and the CR rates were 17%, 23%, 24%, 25%, and 23%, respectively. The international consensus endpoints take into account both the pain score and analgesic consumption. This lowers the CR and PR rates employing the consensus endpoints when compared with the pain-only endpoints. Using international consensus endpoints, a CR rate in the range of 21%–25%, PR rate in the range of 26%–30%, and overall response rate in the range of 46%–50% were noted in our patient population.