Whereas there currently exist a lack of consensus as to which staging modality should be considered as the gold standard for local staging of the tumour (T) and detection of lymph node involvement (N), the use of multi-parametric Magnetic Resonance Imaging (MRI) of the pelvis has been endorsed by international guidelines (NCCN, ESMO/ESTRO).

An expert panel of radiologist and radiation oncologists with expertise in anal cancer diagnosis and treatment identified by the Anal Staging Subgroup of the International Rare Cancer Incentive (IRCI) will be invited to participate. The panelists will be assigned into groups based on the geographical location and local practice. Each panelist will be provided with access to a series of anonymized MRI datasets of patients with newly diagnosed anal cancer and asked to provide a TNM stage as well as to identify sites of involved nodes (using a standardised proforma – Appendix1).  Each case was selected for the presence of MRI sequences like these:

• T2w TSE sagittal [T2-w sagittal turbo spin echo (TSE) sequence covering the pelvis]
• T1w TSE axial [sequence for pelvic nodal detection] 
• T2-w TSE axial [sequence of the pelvis]
• T2w TSE sFOV [high-resolution small-field-of-view T2-w TSE sequences perpendicular and parallel to the anal canal]
• DWI [single shot spin echo-echo planar imaging DWI]
• ADC parametric map [apparent diffusion coefficient (ADC) maps]