5 percent of cancer patients in the U.S. end up in a clinical trial
Is that number true? The page doesn't give any reference.
Actually, it appears to be even lower than this.
From the book A National Cancer Clinical Trials System for the 21st Century by the Institute of Medicine (US) Committee on Cancer Clinical Trials and the NCI Cooperative Group Program, published in 2010:
It is estimated that only 3 percent of adults with cancer participate in clinical trials, and people who are members of racial and ethnic minorities, elderly and low-income individuals, and people who live in rural areas remain underrepresented (EDICT, 2008)
Here's the full detail of that reference:
EDICT. 2008. The EDICT Project: Policy Recommendations to Eliminate Disparities in Clinical Trials . Houston, TX: EDICT Project
I can't find any more up to date primary source, but here's a quote from 2013, quoted in the BBC from the UK's Chief Medical Officer, Prof Dame Sally Davies, which suggests that this particular expert didn't have access to any more recent data suggestive of any sudden increase:
"We [British NHS] put between 15-20% patients into trials in cancer compared to 2-3% in the United States
Here's another 2013 quote, this time from a lobby group on behalf of Asian-American cancer patients calling for more access to clinical trials:
Only 3 percent of adults are enrolled in clinical trials
I've seen many articles simplify this 2-3% estimate to "less than 5%". Here's one example from 2014) in an article discussing why so few US patients access clinical trials.
This appears to confirm that whatever the very latest estimates are (and it's possible they're not be published yet), could certainly be as low as 5%, and may be lower.
The above all refer to "adults with cancer" while the original quote didn't specify adults. However, children make up less than 1% of Americans with cancer so couldn't make up the difference to bring the total up to 5% even if 100% of US children were on clinical trials.