The National Cancer Institute (NCI), part of the National Institutes of Health (NIH) in the Department of Health and Human Services (HHS), stated on its website in the "Cannabis and Cannabinoids (PDQ)" section in Nov. 2014:

“At this time, there is not enough evidence to recommend that patients inhale or ingest Cannabis as a treatment for cancer-related symptoms or side effects of cancer therapy.”

Nov. 2014