Possible Dose-Response Relationship in Palliative Radiotherapy for Non-bone Painful Lesions.

ABSTRACT

AIMS: Total radiation dose does not predict pain response in conventionally fractionated radiotherapy for bone metastases. By contrast, in radiotherapy for solid painful tumours other than bone metastases, it is unknown whether there is a dose-response relationship. We sought to determine whether a higher total radiation dose predicted a higher pain response rate in palliative radiotherapy for non-bone painful lesions. MATERIALS AND METHODS: We carried out a secondary analysis of a prospective observational study. For patients scheduled for radiotherapy for painful tumours, Brief Pain Inventory data were collected at baseline and at 1, 2 and 3 months after the start of radiotherapy. The predictive value of total radiation dose was evaluated using the Fine-Gray model, in which death without a pain response was treated as a competing risk. RESULTS: Of the 203 patients with solid painful tumours, 78 (38%) had non-bone painful lesions. There were no significant differences in pain response rate, the rate of the predominance of non-index pain or reductions in pain interference scores between the patients with non-bone lesions and those with bone metastases. Multivariable analysis showed that total radiation dose was an independent significant predictor of pain response in patients with non-bone painful lesions. This result was not robust to sensitivity analysis with Cox regression analysis. CONCLUSIONS: Higher total radiation dose seemed to be associated with a higher rate of pain response in patients with non-bone painful lesions. However, this finding was not robust to sensitivity analysis. Dose-response relationship should be investigated in clinical trials enrolling patients with these kinds of painful tumour.