OP is talking about the NCCN Guidelines, which doesn't seem to be available in other formats or API. From their website:
NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines®): The NCCN Guidelines® document evidence-based, consensus-driven management to ensure that all patients receive preventive, diagnostic, treatment, and supportive services that are most likely to lead to optimal outcomes.
Format(s) Available for Licensing:
PDF
API not available
NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines®): The NCCN Guidelines® document evidence-based, consensus-driven management to ensure that all patients receive preventive, diagnostic, treatment, and supportive services that are most likely to lead to optimal outcomes.
Format(s) Available for Licensing: PDF API not available