Computed tomography Hounsfield unit values as a treatment response indicator for spinal metastatic lesions in patients with non-small-cell lung cancer: a retrospective study in Japan.

Study design: A retrospective study.

Purpose: This study aimed to determine the impact of increased Hounsfield unit (HU) values for metastatic spinal lesions measured via computed tomography on the overall survival of patients with non-small-cell lung cancer (NSCLC) and identify factors associated with increased HU values in metastatic spinal lesions.

Overview of literature: Previous studies have underscored the utility of the HU as a marker of treatment response in metastatic bone lesions. However, no prior studies have explored the relationship between HU changes in response to treatment and overall survival in patients with NSCLC.

Methods: This study included a total of 85 patients between 2016 and 2021. Nonsurgical treatments were provided by the respiratory medicine department. HU values for metastatic spinal lesions were evaluated upon diagnosis of spinal metastasis (baseline) and at 3, 6, and 12 months thereafter. Patients were then divided into two groups based on the median HU increase from baseline to 3 months. Overall survival was assessed using the Kaplan-Meier method.

Results: Based on the median change in HU value (124), 42 and 43 patients were categorized into the HU responder and non-responder groups, respectively. The median overall survival was significantly longer in the HU responder group than in the HU non-responder group (13.7 months vs. 6.4 months, p <0.001). Multiple linear regression analysis revealed that the use of antiresorptive agents and molecularly targeted therapies were factors significantly associated with an increase in HU.

Conclusions: An increase in HU values for metastatic spinal lesions after 3 months of treatment was correlated with a significantly longer overall survival in patients with NSCLC. Thus, HU measurements may not only serve as an easy and quantitative approach for evaluating treatment response in metastatic spinal lesions but also predict overall survival.