Category of evidence and consensus underlying National Comprehensive Cancer Network guidelines: Is there evidence of progress?

National Comprehensive Cancer Network (NCCN) guidelines are the most comprehensive and widely used standard for clinical care, financial reimbursements and quality improvement initiatives in oncology. We studied the distribution of categories of evidence and consensus (EC) in the guidelines for the common cancers in the United States. We evaluated the EC categories in staging, therapy and surveillance recommendations in 2019 guidelines and compared them with the same in 2010. The latest 2019 version of NCCN guidelines were obtained. The definitions for various categories of EC used were, Category 1 (high level evidence, uniform consensus), Category 2A (lower level of evidence [LOE], uniform consensus), Category 2B (lower LOE, no uniform consensus but with no major disagreement) and Category 3 (any LOE, major disagreement). We compared our results with previously published results from 2010 guidelines. Total number of recommendations increased by 77% from 1023 (2010) to 1818 (2019). Of the 1818 recommendations, Category 1, 2A, 2B and 3 EC were 7%, 87%, 6% and 0%, respectively, while in 2010 they were 6%, 83%, 10% and 1%. Breast (30%), lung (10%) and kidney (10%) cancer had the highest proportions of Category 1 therapeutic recommendations in their respective guidelines. No Category 1 recommendations were found in screening or surveillance guidelines or in pancreatic and uterine cancer guidelines. Recommendations in 2019 NCCN guidelines are largely Category 2A (lower levels of evidence, uniform expert opinion), unchanged from the previous study in 2010.