[refurb]

Yup. And some of those follow on tests could be quite invasive and risky in their own right. With that kind of false positive rate, you'd be risking the life of a not insignificant number of people.

Either that or driving up healthcare costs significantly as those 5000 people are going to need an MRI or CAT scan or something else to rule out cancer.

[nugget]

What follow on test for suspected lung cancer would risk the life of a not insignificant number of people?

An MRI without contrast has no impact. An MRI with contrast has relatively little impact. A biopsy would only be done if the MRI with contrast lit up areas of concern. At the point a PET is ordered, you have narrowed the false positive pool substantially and probably want the scan no matter what.

[zxcmx]

Just telling millions of people per year they might have cancer... say the MRI is booked for 2 weeks out... which they are then going to majorly stress about the whole time regardless of how low you tell them the risk is - is going to have some crazy societal impact.

[hermitdev]

I typically have several MRIs per year. I'm not claustrophobic and don't stress about them, but sometimes MRIs cause me physical discomfort, even without contrast. With contrast, its slightly worse, it seems.

I think its related to a genetic disorder that causes me to retain high levels of iron, but I have nothing to back this up.

This discomfort in the MRI comes in the form of waves of warmth I feel throughout my abdomen. Its mostly annoying/distracting and not painful. The loudness of the MRI is far worse than the slight warming I feel. Less annoying than the pee your pants feel of a CT with contrast.

[happysadpanda2]

I believe the stress would come from the uncertainty of whether or not they have cancer, not from going into the MRI machine.

Just looking at myself, I feel a great level of distress over other, less serious, variations of uncertainty. Having been told I might have cancer, and then not getting to know for certain this very instant would be nothing short of nerve-wracking...

[efournie]

The warmth is caused by the RF pulses and has nothing to do with the magnet or iron levels. Basically the scanner behaves the same as a microwave oven.

That's why you have to enter the patient weight and size before scanning, in order to keep the SAR within acceptable values and limit body heating.

[rdlecler1]

My father has hemochromatosis which causes high iron uptake. He didn’t discover this until his fifties and it’s like he has rust in his joints. I did 23andMe and I only have one allele so I don’t have it. If you suspect you do, a dna rest will tell you. Please get that checked out. You can deal with it if it’s early in your life.

[hermitdev]

Ive been tested, and I have hemachromatosis. That's what my next MRI is for - to check on my liver.

So far, for me, it's monitoring. Some dietary changes such as cutting back on red meat and high iron vegetables (mostly cut out spinach, which sucks because I've loved spinach my entire life, especially the Greek dish spanikopita).

My blood iron levels fluctuate a lot based upon diet. Ive mostly got it under control, but normal for me is still on the high end of the normal ramge for normal people.

It probably went undiagnosed for a long time because I used to give blood regularly, but had to stop when my work hours changed to be 7am-7pm and could not make it to a facility to donate. Thats when blood tests started ahowing a problem. Not yet to scheduled phlebotemy, but probably the best option if it becomes an issue.

[robbiep]

Quite rare to jump straight to an MRI - a chest MRI is a half hour deal. More common to do a CT Chest which has a 1:500 risk of causing cancer

[maneesh]

Does this mean that out of the 5000 false positives, 10 people will actually GET cancer by doing a follow-up CT exam?

[pmiller2]

We don't really know. Data that show X dose of radiation increases the probability of developing cancer by Y% is based on studies on survivors of atomic blasts. The number of people exposed to an amount of radiation equivalent to a handful of CT scans is pretty small relative to the effect size that's claimed, so there is reason to be skeptical.

See https://www.scientificamerican.com/article/how-much-ct-scans... for a jumping off point into this type of research.

[chrisweekly]

"1:500 risk" - citation?

[robbiep]

https://www.health.harvard.edu/staying-healthy/do-ct-scans-c...

Looks like I may have been misrepresenting the risk to some patients; also looks like i've probably caused around 4 cases of cancer

[sambe]

It doesn't have to instantly and directly kill somebody to be bad in aggregate.

This kind of analysis has been done, most memorably for breast cancer screening. The conclusion I recall was that it did more harm than good a few years ago (opportunity cost of unnecessary spending, pain and complications of biopsy, unnecessary mastectomy, psychological damage, etc. etc.). The follow-up tests and analysis also have an error rate and no treatment is zero cost.

[refurb]

Not only the risk of contrast agents, but possible sedation or just plain medical errors.

It might only be 1 or 2 people out of 5,000, but those 5,000 were perfectly healthy and never had cancer to start with.

[mirimir]

That's also why there was no screening for thyroid cancer after above-ground nuclear weapons testing. Thyroid cancer itself isn't that hard to treat. So the risk of follow-on testing outweighed cancer risk.