This scoping review mapped the main themes in existing expert guidelines for cancer care issued during the COVID-19 crisis from the period of March 2020-August 2021. The guidelines published during the research period principally relate to the first two waves in Europe and until the beginning of the vaccination campaign. They elaborated recommendations for cancer care reorganisation, in particular triage and quality of care issues. The article highlights the ethical, epistemological, as well as practical reasons that guidelines were not always followed to provide some lessons learned for future crises to enable better guideline development processes. We also elaborate early evidence on the impact of triage decisions and different perspectives on cancer care reorganisation from ethics and social science literature.