Exploring definitions of radiological sarcopenia in cancer: a protocol for a scoping review

INTRODUCTION: Sarcopenia is the loss of skeletal muscle volume or quality, a concept previously established in age-related frailty. Sarcopenia is part of the cancer cachexia syndrome and has therefore been explored as biomarker through the opportunistic measurement of skeletal muscle from routine cancer imaging. However, there is inconsistency in diagnostic landmarks and cut-offs. The most common assessment method is skeletal muscle area at the slice level of the third lumbar vertebrae divided by height squared. Alternative sarcopenia measures have been derived from morphological descriptions of the psoas, thoracic and cervical muscles, driven by tumour-specific anatomical imaging. Current tumour-site specific reviews suggest a link between heterogeneously defined sarcopenia on tumour site-specific outcomes. Because lack of uniformity, a scoping review is best suited to streamline anatomically based definitions and map the evidence to outcomes. The aim of this article is to describe a protocol for a scoping review that will homogenise the evidence of radiological sarcopenia in cancer. The extent, range and nature of reports will be examined, after which possible titles for potential systematic reviews identified. METHODS AND ANALYSIS: We will apply methods based on the Joanna Briggs Institute scoping review manual. Predefined search terms compiled with a librarian experienced in systematic reviews will be used to search PubMed/Medline, Embase, Scopus and Cochrane databases studies correlating cross-sectional cancer sarcopenia biomarkers with clinical outcomes. Studies will be mapped according to whether they have defined new sarcopenia measures or applied previous definitions to new populations, both with reported outcomes. This review will generate a numerical analysis on the extent of cancer sarcopenia measures as well as a narrative synthesis to describe the applications of radiologically derived sarcopenia in cancer. ETHICS AND DISSEMINATION: Formal ethical approval was not required to undertake this scoping review. Findings will be published in peer-reviewed journals and conference presentations.