Table 1.

Levels of evidence and recommendation grades from American Society of Clinical Oncology (ASCO)

Levels of evidence

I. Evidence from meta-analysis focusing on well-designed and controlled trials. Randomized trials with low incidence of false negatives or positives

II. Evidence from at least one well-designed experimental study. Randomized trials with high incidence of false negatives or positives

III. Evidence from well designed but no randomized trial: phase I/II trials, cohorts, and case–control study

IV. Evidence from non-experimental trials as observational studies

V. Evidence from cases and clinical examples

Recommendation grades

A. There is a type I evidence or consistent findings in multiple studies with evidence II, III, or IV

B. There is a type II, III, or IV with mostly consistent findings

C. There is a type II, III, or IV with mostly inconsistent findings

D. There is scarce or no systematic empiric evidence