New Clues on Colorectal Cancer Among Young Adults

It’s a long-running medical mystery: Why have so many people under 50 in affluent countries been developing colorectal cancer in recent decades?

Something new is triggering a jump in what’s known as early-onset colon and rectal cancer (EOCRC). The rates have been going up for the last 20 years and no one knows why it’s happening. The usual risk factors for CRC —obesity, smoking, bad diet and lack of exercise— don’t fully explain the increase.

Source: Health, June 7, 2024

Five years ago, De-Kun Li, a senior epidemiologist at Kaiser Permanente in Oakland, CA, offered a new possibility: carrying a cell phone below the waist. When placed in a pocket below the belt, the phone transmits RF radiation into the abdomen. Given that RF has been shown to cause cancer in animal experiments, Li thought it was a plausible risk factor. (This is what I wrote at the time.)

The idea didn’t catch on, but Li persisted and conducted a pilot study to test his hypothesis. It convinced him that he may be onto something.

It’s a small study, designed to survey 50 cases of EOCRC and 50 matched controls. He found that those who carried a phone below the waist were four times more likely to develop tumors.

EOCRC Tumors on the Left Side

Li found that the link between cell phone carrying and EOCRC is strongest when the phone was kept on the same side as where the tumor developed.

EOCRC tends to develop on the left side of the colon. Those who carried a phone on the left side for more than 30,000 hours were 12 times more likely to develop a tumor on that side of the colon. This elevated risk for what’s called ipsilateral carrying is statistically significant. (36,000 hours is equivalent to about ten years of RF exposure.)

Those who kept the phone on their right side —contralateral carrying— had only a slightly increased CRC risk for left-side colon cancer, according to Li.

“The striking contrast between a strong association with ipsilateral carrying and largely no association with contralateral carrying is the most notable finding,” Li told me in an email exchange.

There were not enough cases of right-side colon cancer for a right-side carrying risk analysis in this pilot study, but Li believes that if his hypothesis is correct and he were able to do a larger study, a similarly elevated risk would be seen for right-side ipsilateral carrying.

Li presented his results in late August at the annual conference of the International Society of Environmental Epidemiology (ISEE), held this year in Santiago, Chile. His poster paper is below; the ISEE abstract is here.

 De-Kun Li’s Poster Presentation at ISEE 2024 in Santiago (click to expand)

Another Opinion

As it happened, Kurt Straif was also going to the Santiago meeting, and I asked him to check out Li’s paper. Straif, formerly the head of the IARC Monograph Section in Lyon, now has appointments at Boston College in the U.S. and ISGlobal in Spain. He oversaw the 2011 IARC meeting where RF radiation was judged to be a possible human carcinogen. Straif is currently a member of the team preparing a systematic review of the RF–animal cancer literature for the WHO’s EMF Project.

“I’m skeptical,” Straif told me when he got back from Chile. “It’s a small study reporting implausibly strong associations with very wide confidence intervals.” Straif is not yet willing to discount the existing CRC risk factors for the rise in EOCRC. They —particularly obesity— are still “plausible, at least partially,” he said, especially given that there is “no robust evidence for new risk factors, environmental or otherwise.”

In any case, Straif continued, the timing is off: Widespread use of mobile phones among younger people “comes only after the dramatic increase of EOCRC, especially when you take into account a latency period between exposure and disease.”

I asked Li to address Straif’s concerns. He acknowledged that the numerical risk estimates should not be taken too literally given the relatively small sample size of the pilot study. “They could have been smaller or larger,” he said. “It’s the striking difference between the ipsilateral and contralateral risks that we should pay attention to.”

Li also disagrees with Straif on the timing: “Cell phones became popular before the steady rise in EOCRC incidence,” he said. “Of course, the unknown part is the latency: We do not know how long the latency is for EOCRC.”

“Please remember that genetically susceptible individuals will get EOCRC first whenever a new environmental risk factor enters the fray,” Li said.

American Cancer Society Not on Board

I sought a second opinion from Rebecca Siegel, a senior researcher at the American Cancer Society. Siegel publishes regular updates on CRC statistics and has for years raised concern over the increasing rates of EOCRC among the young —against the backdrop of the declining rates among those over 50 (late onset CRC).

I sent Siegel Li’s abstract and asked her whether, given the lack of progress* in explaining the rise in EOCRC, Li’s results are persuasive enough to go forward with a more statistically reliable study.

“Very interesting,” Siegel replied, but then all but dismissed Li’s hypothesis. She also questioned the timing: It “doesn’t really work because rectal cancer rates have been increasing since the 1970s and 1980s in people in their 20s and 30s,” she wrote, “and cell phone use did not become widespread until the 2000s, with later uptake among kids and teens.”

“Actually, cell phone use started to take off in the mid-1990s,” Li said. In 1992, for instance, about 11 million Americans were using cell phones, according to CTIA, the wireless trade association. By 1996, the number had grown to more than 44 million, and close to 110 million in 2000.

As to when rates of EOCRC increased, Li said the big jump happened quite a bit later than the 1970s and 1980s. He cites a 2022 review by Frank Sinicrope of the Mayo Clinic in the New England Journal of Medicine. Sinicrope states that you can see a “clear change” in EOCRC incidence in the U.S. data: It began in 1994 and ushered in a steady upward trend. “Similar observations of the rising incidence of EOCRC have been reported in other high-income countries,” he wrote.

For instance, Sinicrope cites a study of EOCRC rates in 20 European countries, which found that, on average, CRC incidence increased by 7.9% per year among subjects aged 20–29  from 2004 to 2016. The study was published in Gut, a BMJ journal, in 2019.

The EOCRC incidence trends in Canada for men and women below show a clear rise beginning in the late 1990s and early 2000s.

 Source: JAMA Open, July 31, 2019 (click to expand)

What Now?

In the end, neither Straif nor Siegel would endorse a larger study to fully test Li’s hypothesis.

As for the next step, Li is planning to apply for federal funding to do a larger study. “If my hypothesis is correct,” he said, “it carries great public health significance because just about the entire population may be at risk.”

In closing, Li stressed that even if carrying a cell phone below the waist only partially explains the rise of EOCRC, it’s “easily preventable”: “All you would need is public education; it wouldn’t cost anything more.”

An Early Warning

We may have had a warning about the dangers of putting transmitters in our trousers —or under them— some 30 years ago.

In January 1997, the U.K. Sunday Times reported that three members of an elite police unit (E4A) of the Royal Ulster Constabulary (RUC) had died of colon cancer, after doing undercover surveillance work in Northern Ireland. The officers concealed radio transmitters “in the small of the back or next to the kidneys,” the newspaper was told (see clip below and MWN, J/F97.)

“The detectives were in their thirties and cancer of the colon usually affects people in their fifties,” the Sunday Times stated.

“Concerns over police radio safety were similar to those over mobile phone emissions,” a police health and safety official told the Times.

(click to expand)

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FOOTNOTE

* Progress on finding a cause for EOCRC has been elusive. Here’s an example of how little has changed: Between 2017 and 2023, Siegel published three statistical reviews of CRC. Each closes with the same call for more research on what is driving the jump in EOCRC:
  • 2017: “Finally, more research is needed to elucidate causes for the increasing burden of CRC in young adults…”
  • 2020: “In addition, research is needed to elucidate causes for the rising CRC incidence in young and middle-aged adults…”
  • 2023: “In addition, research is needed to elucidate causes for rising CRC incidence…”