Does re-ossification after palliative radiotherapy for spinal bone metastases help maintain vertebral body height?

Abstract

Background context: After palliative radiotherapy of spinal bone metastases, re-ossification is sometimes observed in bone with osteolytic changes. However, it remains unknown whether the re-ossification that is observed after radiotherapy is associated with preservation of vertebral body height.

Purpose: To investigate whether re-ossification observed after palliative radiotherapy can contribute to the preservation of vertebral body height.

Study design: This is a retrospective observational study.

Patients sample: We investigated 111 vertebral bodies in 54 patients that underwent palliative radiotherapy at a single center for painful osteolytic/mixed metastatic spinal tumors in solid tumors between 2016 and 2020.

Outcome measures: The outcome measures were the presence of re-ossification and vertebral body height reduction on the CT image.

Methods: Re-ossification was evaluated according to the MD Anderson response classification criteria, and sagittal CT images were used to evaluate vertebral body height. A vertebral body ID was assigned to the irradiated vertebral body, and continuous CT images obtained for each vertebral body ID were evaluated. The median number of evaluation periods for each vertebral body was 4, and the total number of periods was 463. Logistic regression analysis was performed to investigate factors related to the occurrence of vertebral body height reduction before the subsequent CT. As a subanalysis, factors related to re-ossification were investigated.

Results: The following primary cancer types were observed: lung cancer, 41 vertebral bodies; breast cancer, 19; renal cell cancer, 15; other, 36. A total of 62.2% showed re-ossification. The median time to confirmation of re-ossification by CT was 2 months. Factors significantly associated with vertebral body height reduction were presence of vertebral body height reduction before radiotherapy (odds ratio [OR] 6.8, 95% confidence interval [CI] 2.0-63, p=.01) and no re-ossification (OR 137, 95% CI 22-3469, p<.01). Factors associated with re-ossification were the type of cancer and total radiation dose. Those with lung cancer and those with a total radiation dose of 20 Gy or less were more prone to re-ossification.

Conclusions: Re-ossification was observed in 62.2% of vertebral bodies after palliative radiotherapy for painful osteolytic/mixed metastatic spinal tumors. The re-ossification group demonstrated significantly less vertebral body height reduction when compared with the non-re-ossification group. The presence of re-ossification may potentially serve an important role in maintaining vertebral body height.

Keywords: CT; Lung cancer; Palliative radiotherapy; Re-ossification; Spinal bone metastases; Vertebral body height reduction.