Minimal clinically important differences in the Spine Oncology Study Group Outcomes Questionnaire (SOSGOQ2.0) in patients with symptomatic spinal metastases.

BACKGROUND CONTEXT: It is currently unknown what absolute change in Spine Oncology Study Group Outcomes Questionnaire (SOSGOQ2.0) represents a clinically meaningful change for a patient which causes challenges with the interpretation of the SOSGOQ2.0 total score or domain scores.

PURPOSE: The aim of this study was to determine the minimally clinically important difference (MCID) for the SOSGOQ2.0 in patients with spinal metastases.

STUDY

DESIGN

An international multicenter prospective observational study by the AO Spine Knowledge Forum Tumor.

PATIENT SAMPLE: Patients with spinal metastases who were treated with surgery and/or radiotherapy OUTCOME MEASURES: Health related quality of life (HRQOL) was evaluated using the SOSGOQ2.0 at predefined time points

METHODS

The MCID values for the SOSGOQ2.0 were determined using both distribution-based as well as anchor-based methods. For the anchor-based method, the posttherapy questions of the SOSGOQ2.0 served as the anchor with response options collapsed into "improvement," "no change" and "deterioration." Spearman correlation coefficients were calculated to identify posttherapy items with a correlation of ≥0.30 with the corresponding domain scores. MCID values from the distribution-based methods were derived using the statistical characteristics of the study population and compared to the anchor-based results.

RESULTS

A total of 317 patients had SOSGOQ2.0 data available at baseline and at 12 weeks posttreatment and were included in the final analyses. Anchor-based MCID values for improvement in the physical function, pain, mental health and social function domains were 10.2, 26.0, 14.4 and 17.2 respectively. Compared with the distribution-based approach, anchor-based MCIDs for improvement suggest that the patient-perceived improvement corresponds to a strong level of improvement.

CONCLUSIONS

This is the first study to report MCID values for the SOSGOQ2.0 total score and domain scores. The distribution-based MCID estimates will help both clinicians as well as researchers with the interpretation of the effect of treatment for painful spinal metastases on patient reported health related quality of life (HRQOL).

TRIAL REGISTRATION: Clinical trials identifier NCT01825161.