Level of Scientific Evidence Underlying the National Comprehensive Cancer Network Clinical Practice Guidelines for Hematologic Malignancies: Are We Moving Forward?

Background: The level of scientific evidence in National Comprehensive Cancer Network (NCCN) guidelines for malignant hematological conditions haven't been recently investigated. We describe the distribution of categories of evidence and consensus (EC) among the 10 most common hematologic malignancies with regard to recommendations for staging, initial and salvage therapy, and surveillance. Methods: We reviewed the level of evidence for the 10 most common hematological malignancies by incidence in the United States as of 2020. The NCCN definitions for EC are: category 1, high level of evidence, such as randomized controlled trials, with uniform consensus; category 2A, lower level of evidence with uniform consensus; category 2B, lower level of evidence without a uniform consensus but with no major disagreement; and category 3, any level of evidence but with major disagreement. We compared our results with previously published results from 2011. Results: Of 1353 recommendations, 5%, 91%, 4%, and 1% fell into EC categories 1, 2A, 2B, and 3, respectively, while in 2011 the comparable percentages were 3%, 93%, 4%, and 0%, respectively. Recommendations with category 1 EC were found in all guidelines, except for Burkitt lymphoma. Of all therapeutic recommendations, 6.3% were category 1 EC, with the majority of these (56.4%) pertaining to initial therapy. Guidelines with highest proportions of therapeutic recommendations with category 1 EC were multiple myeloma (12.4%), chronic lymphocytic leukemia/small lymphocytic lymphoma (6.9%), and acute myeloid leukemia (5.6%). Conclusions: Recommendations in the 2020 NCCN guidelines are largely developed from lower levels of evidence but with uniform expert opinion, underscoring the urgent need and available opportunities to expand the current evidence base in malignant hematological disorders.