Comment by Gatsky | Hacker News Reader

Comment by Gatsky | Hacker News Reader

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The effect sizes of carcinogenic (or potentially carcinogenic) environmental risk factors are small compared to the very high baseline risk of getting cancer over the long lifetimes we are blessed with. Some cancers, like prostate cancer, don't have any proven environmental or lifestyle risk factors.

Consider smoking - the exposure of the lungs to cigarette smoke is very high and very consistent compared to almost all other environmental exposures which are also generally less carcinogenic.

The key question is - are cancers getting more common without a good explanation [1], and if so which ones? The answer is that upper gastrointestinal cancers do some to be getting more common. These are plausibly due to dietary changes and/or obesity. Personally, I think ingesting huge amounts of added sugar, particularly fructose, is the potential unifying culprit.

[1] Many cancers are increasing in incidence because of better screening and detection. Breast cancer is a good example. Other cancers like leukaemia or pancreatic cancer couldn't even be reliably diagnosed 100 years ago, so obviously they are more common today.

"cancers like leukaemia or pancreatic cancer couldn't even be reliably diagnosed 100 years ago,"

That's only partially true. They could still do an autopsy to figure it out. Maybe less common.

Either way, cancer rates in you people have increased 30% since the 70s. And that's considering that smoking rates have decreased during that time.

>Some cancers, like prostate cancer, don't have any proven environmental or lifestyle risk factors.

Prostate cancer is associated with contracting STD's:

https://pubmed.ncbi.nlm.nih.gov/15988645/

Conclusions: This meta-analysis provides evidence of a higher rate of prostate cancer in men with a history of an exposure to gonorrhea, HPV, or any STD.

This evidence is preliminary and the odds ratios are small. Also, consider the very high prevalence of prostate cancer - it is implausible that STDs are a major or important cause.

According to the CDC the majority of sexually active adults in the US will get HPV at some point in their lives.

HPV is extremely common, usually asymptomatic, and already known to contribute to other reproductive cancers. Why is it "implausible"? It seems this study at least shows it is plausible.

The effect is weak. The ubiquity of HPV infection should show a stronger association if it were important. It could contribute to a subset of prostate cancers, but this has not been proven beyond correlation. There are other issues - HPV related cancers like cervical cancer or head and neck cancer show an age related peak and decline, whereas prostate cancer incidence continues to rise with age.

But the HPV vaccine is certainly worth having for males that have not engaged in any sexual activity.

True, it's interesting that it doesn't peak. Is that initial onset, or simply occurance?

I ask that because prostate cancer has a very positive long term survival rate but also recurs in almost a third of cases. I wonder if the peak in other cancers is because long term survival is lower, or lomg term survival is also high but recurrence is lower.

That is incidence, ie first diagnosis for the patient.

Other HPV related cancers like head and neck cancers tend to have a good prognosis.

HPV almost certainly doesn’t cause direct viral oncogenesis in prostate ca. It may cause chronic inflammation which promotes prostate cancer. It may also infect/accelerate already malignant cells - this is the likely mechanism in nasopharyngeal carcinoma and EBV.

The effect will necessarily appear weak when incidence of HPV is over 80%. At 95% it would appear weaker yet. That any signal shows up under the circumstances means the effect is huge.

With respect, this isn’t an accurate interpretation of an odds ratio. If you look at other cancers with a clear viral cause (EBV and nasopharyngeal carcinoma, HPV and cervical cancer), you will see that nearly 100% of tumours show evidence of viral infection and the odds ratios are very high, even though the viruses are ubiquitous.

The data for HPV and prostate cancer suggest, at best, an indirect effect such as inflammation rather than direct viral oncogenesis.

In any case, how do you modify this potential risk factor? Celibacy or vaccination. As I said, I would encourage any teenage male to get the HPV vaccine. It is worth paying for, if you can.

For cancer categories that are caused only by HPV, the signal would be clear even at 95%. But many categories have multiple possible causes. A cancer that could be caused by HPV or something else is still sufficient reason to get vaccinated.

Everybody not already exposed to HPV should get vaccinated against it. All insurance companies should be obliged to pay for such vaccinations.

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