The ESMO Magnitude of Clinical Benefit Scale (ESMO-MCBS) version 1.0 (v1.0) was published in May 2015 and was the first version of a validated and reproducible tool to assess the magnitude of clinical benefit from new cancer therapies. The ESMO-MCBS was designed to be a dynamic tool with planned revisions and updates based upon recognition of expanding needs and shortcomings identified since the last review. The revision process for the ESMO-MCBS incorporates a nine-step process: Careful review of critiques and suggestions, and identification of problems in the application of v1.0; Identification of shortcomings for revision in the upcoming version; Proposal and evaluation of solutions to address identified shortcomings; Field testing of solutions; Preparation of a near-final revised version for peer review for reasonableness by members of the ESMO Faculty and Guidelines Committee; Amendments based on peer review for reasonableness; Near-final review by members of the ESMO-MCBS Working Group and the ESMO Executive Board; Final amendments; Final review and approval by members of the ESMO-MCBS Working Group and the ESMO Executive Board. Twelve issues for revision or amendment were proposed for consideration; proposed amendments were formulated for eight identified shortcomings. The proposed amendments are classified as either structural, technical, immunotherapy triggered or nuanced. All amendments were field tested in a wide range of studies comparing scores generated with ESMO-MCBS v1.0 and version 1.1 (v1.1). ESMO-MCBS v1.1 incorporates 10 revisions and will allow for scoring of single-arm studies. Scoring remains very stable; revisions in v1.1 alter the scores of only 12 out of 118 comparative studies and facilitate scoring for single-arm studies.