Spinal tumors confer significant morbidity and mortality on patients and can be broadly classified as primary or metastatic. Primary tumors originate from the spinal column or adjacent structures and comprise just 3% of spinal tumors in adults. Metastatic spinal tumors are far more prevalent and spread through hematogenous systems, with the thoracic and thoracolumbar regions most commonly affected.1 A postmortem study found the prevalence of metastatic spinal disease to be between 70% and 90% in patients with prostate or breast cancer.1,2 The increasing prevalence of metastatic spinal tumors can be attributed to improved cancer survival rates due to more advanced medical treatment and complex surgical management, with up to 70% of cancer patients developing spinal metastases.3,4 Patients may experience pain and neurological impairment that impacts their physical, psychological, social, and emotional well-being, thus a major goal of treatment focuses on improving a patient's health-related quality of life.5

Patient-reported outcomes (PROs) represent a patient's impression on their current health status and impact on multiple aspects of their life.6 PROs aid surgeons in gauging response to treatments, framing expectations with patients, and facilitating informed, collaborative decision making.7 Thorough communication and education has been demonstrated to augment postintervention PROs, which remains an area for improvement in spine tumor literature as there remains evidence of discordant physician-patient expectations regarding prognosis and goals of treatment [2, 6, 7].

Few PROs focusing on spine tumor patients have been described in the literature. It is important for health care providers to have access to a reliable and comprehensive outcome measure to optimize assessment of patient's health and the effectiveness of spinal tumor treatment.8 The purpose of this review is to synthesize current literature to comprehensively assess the utility of PRO tools in the treatment of spinal tumors.

The Oswestry Disability Index (ODI) and Neck Disability Index (NDI) are traditionally the most commonly used outcomes tools in spine surgery literature for lower back and neck pain, respectively.8 Other generic PRO measures used in the clinical setting include 36-Item Short Form Survey (SF-36), Sickness Impact Profile, Nottingham Health Profile, and EuroQol-5D (EQ-5D). There are also generic cancer PRO measures which include the Functional Assessment of Cancer Therapy, Health Utilities Index, Eastern Cooperative Oncology Group Performance Status, and The European Organization for Research and Treatment of Cancer Quality of Life Questionnaire Core 30.9 Street et al. compared these 2 categories of PROS and performed an Internal Classification of Functioning, Disability, and Health (ICF) linkage analysis. The ICF is part of WHO’S group of international health classifications and is used as a universal framework for assessing health status and functionality, while not an outcome measurement tool itself.9, 10, 11, 12 In comparing content validity, they found that the Eastern Cooperative Oncology Group and SF-36 were the most valid and reliable based on frequency of citation and correlation with ICF. They concluded that Eastern Cooperative Oncology Group and SF-36 are viable options to assess outcome in spinal metastatic disease patients in the absence of a metastatic spinal-tumor-specific questionnaire. However, in their literature review of 141 studies which utilized various PRO tools in spinal metastatic patients, there was no consensus on the use of 1 PROM measure for spinal metastatic disease. None of the generic PRO tools have been validated in the metastatic spinal tumor population since the patient's specific health concerns are not addressed.9 Generic spine PRO tool are criticized for poor sensitivity and specificity to nuances in health and symptoms due to spine tumor patients' disease or treatment intervention.10

The Spine Oncology Study Group (SOSG) created the Spine Oncology Study Group Outcome Questionnaire (SOSG-OQ) in 2010, specifically for the self-assessment of patients with metastatic disease of the spine. The SOSG-OQ was evaluated and formulated using the ICF, and covers 6 domains including physical function, neural function, pain, social function, mental health, and a post-treatment arm. Additionally, 56 concepts comprise the SOSG-OQ, which are considered any single factor that impacts a patient's health. There are 4 domains within the ICF which include bodily structures, body functions, activity and participation, and environmental factors.10 Multiple studies have compared the content and conceptual agreement between PRO measures and ICF for various diagnosis including cancers.12, 13, 14, 15 Street el al. evaluated content validity of the SOSGOQ by identifying concepts in the questionnaire and determining concept linkage to the ICF according to the hierarchical arrangement of the domain (chapter, second, third, and fourth level domains). The hierarchical linkage and interobserver agreement of linkage confirmed the content validity of SOSGOQ and appropriately identified all 4 core domains of ICF within the SOSGOQ questionnaire. Additionally, 34 concepts were found to be unique meaning that the content appropriately measures patient's health impact. Comparatively, ODI covered 3 domains of the ICF and had 16 unique concepts. This suggest that SOSGOQ is encompasses all required domains to measure appropriate functionality and has superior content to measure patient's health quality due to their metastatic spinal disease.10

Multiple studies validated SOSGOQ and identified greater internal consistency, marking substantial progress in spine-tumor specific PROs. Janssen et al. validated the SOSGOQ and demonstrated that it had better internal consistency and coverage than the EQ-5D. However, exploratory factor analysis hinted the need of a revised SOSGOQ version.16 Versteeg et al. analyzed the psychometric properties and clinical validity of the revised SOSGOQ 2.0 version in patients with metastatic spinal tumors. Confirmatory factor analysis was first performed to develop a revised SOSGOQ 2.0 version with improved conceptual correlation between the items and domains. SOSGOQ 2.0 has 4 domains, 4 distinct individual items, and a set of follow-up questions. This version demonstrated improved construct validity, test-retest reliability, and clinical validity. Additionally, concurrent validity was evaluated comparing to the PRO instruments, SF-36 and numeric rating scale, with a strong correlation between the domains of SOSGOQ and both generic tools.5 Along with HQROL tools, it is important to measure the economic burden of metastatic spine care. This can be achieved by calculating quality-adjusted life years using utilities for spinal metastases to assist with resource allocation and treatment decisions.17,18 Multiattribute utility functions have been used for the conversion of generic pro tools to utilities. Pahuta et al. shortened the SOSGOQ to the SOSGOQ 8D and quantified multiattribute utility functions using Discrete Choice Experiment (DCE) methodology. The multiattribute utility functions can help quantify the desirability of a particular health state as compared to perfect health and the importance of items on the SOSQOQ 8D.18

Despite originating in English, SOSGOQ 2.0 has been translated into numerous different languages and applied to culturally diverse populations worldwide. Multiple studies have sought to assess whether translated versions maintain the validity and consistency of their origin. Brodano et al. developed the Italian version of SOSGOQ 2.0 which maintained construct validity and acceptable internal consistency when evaluating the metastatic spinal tumor patient population. Additionally, concurrent validity was confirmed with good correlation to the SF-36.19 Gal et al. demonstrated that the Dutch SOSGOQ 2.0 had good internal consistency, test-retest reliability, and convergent validity with the SF-36 for all the domains when item 20 was removed from the social function domain.20 Yin et al. found excellent internal consistency, test-retest reliability, and score distribution for the Chinese SOSGOQ 2.0.21 Luksanapruksa et al. found the Thai SOSGOQ 2.0 to be acceptable in terms of validity, internal consistency, and test-retest reliability.22 SOSGOQ remains a gold standard, validated PRO tool for the metastatic spine population, and may be effectively administered in English and a myriad of other languages. However, there is a lack of consensus regarding the use of a PRO tool for all spinal tumor patients.