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John Cohen, MDCM, PhD

Q: I had a question about the cancer discussion tonight that I didn't get to ask. If so many cancers progress in the pre-clinical phase (and by the time they're detected they're so advanced), why don't we all get preventative CAT scans (or something) once a year to check for cancer?
A: As with all things in medicine (in life, too) there needs to be a cost-benefit calculation. A full-body CAT scan would expose the average person to a significant amount of radiation, and on a yearly basis, it would eventually be blamed for causing some cancers; maybe more than it detected! In addition, the per-patient cost would be huge: Not having any suspicions, the entire scan would have to be studied minutely by an expert, and that would require more experts (and the specialty residency training costs over $500,000); plus the fear of a lawsuit if someone missed a tiny lesion would keep most radiologists out of that business.

Q: What about Dariush Mozaffarian's analyses that indicate it's not the red meat that's dangerous so much as the salted processed meats (Harvard new met analyses)?
A: Interesting. Like most other large series analyzed, it’s probably not definitive and will no doubt be challenged in a few years by another study. Processed meats, though, have a long-lasting bad rap, and in regions where pickled meats constitute a large portion of the diet, the incidence of gastrointestinal cancer is high.

Q: What about the increased incidence of metabolic syndrome associated with eating more carbs than the body can handle? Isn't that a risk factor for increased cancer as well?
A: There is an increased incidence of certain cancers in people with the metabolic syndrome. However, it is quite small and there’s no evidence that the metabolic syndrome causes the cancers. That said, it is known that cancer is associated with chronic inflammation, and so is metabolic syndrome. I don’t know whether weight loss and control of pre-diabetes would reduce cancer risk, but it’s one more prudent reason to try to maintain a BMI in the normal range.

Q: Could you explain why cells without telomeres divide continuously and cells stop dividing as their telomeres get short. This is kind of paradoxical.
A: It seems so, but probably isn’t. Cancer cells upregulate telomerase, which lengthens the telomeres after each cell division, so the cells can divide indefinitely. The loss of telomeres by staining should be regarded as visible evidence the there is something bad going on at the DNA level; it could actually represent a breakage of two chromosomes with subsequent joining of 2 different halves, with loss of the telomeres and so: no brakes.

Q: What makes tobacco such a bad carcinogen as opposed to others?
A: Tobacco is smoked in cigarettes at just the right temperature to catalyze all sorts of interesting reactions, including the formation of benzene rings and long unsaturated hydrocarbon chains; these are potent carcinogens. What isn’t known with any certainty is whether other burning plant leaves, like the type recently approved by Colorado voters, are just as carcinogenic; but I wouldn’t bet my health that they’re not.

Q: If we have a balanced diet AND take supplements is there less risk in taking supplements? Might have misheard you, thought you said "supplements can be carcinogenic"?
A: No, I didn’t say that. But a very recent study showed no effects at all, good or bad, in a cohort of normal people taking supplements for years. I guess it shows that when enough is adequate, more is not better. There are relatively few vitamin deficient people in the USA; even the reports that many are vitamin D deficient are still controversial.

Q: What has caused the significant decrease in uterine cancer since the 30s?
A: It seems to be mostly because the incidence of cervical cancer has fallen. This is due largely to the Pap smear test, and the new HPV vaccine will lower it even more, especially if males start getting immunized more.

Q: What is squamous cell cancer? My dermatologist says it's not really cancer. That's confusing.
A: The skin is a layered tissue, with stem cells (basal cells) at the bottom that differentiate into flattened squamous (“scaly”) cells as they mature and move up. So squamous cell carcinoma is composed of cells that look as though they originated from squamous cells. Basal cell carcinomas are sun-induced and are the most common human cancer. They may invade locally but hardly ever metastasize. Squamous cell carcinomas, less common, tend to invade and spread, so early diagnosis is important. It really is cancer, so maybe there was a miscommunication.

Q: How do genetics come into play for cancer or stroke, in that a paternal aunt having had T.I.A. strokes and breast cancer? It is interesting to learn about a woman on the father's side of a family and how it might be a predictor of health issues in later generations.
A: We are now able to look at the complete sequences of large numbers of people’s DNA, and compare what’s found, say, in 1000 people with cancer and 1000 without it. For diseases like cancer and stroke, so far the answer is: a lot of genes each seem to exert a tiny effect, so with a few exceptions, it isn’t possible yet to look at risk except to say well, there’s cancer in this family, so everyone has a small statistically increased risk. One day we may be able to do better. But remember, all diseases are due to: genetics, environment, and bad luck.