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Comment by gullywhumper | Hacker News Reader

2.5 years in of regular PET scans. At this point, I’m almost humored by what gets flagged as suspicious by the radiologist - usually mosquito bites and stomach bugs (kids in daycare means I’m almost always sick). I have a scan Monday and two weeks ago had a re-excision so there’s a two inch gash healing on my back. This week I got three vaccines. And then tonight my toddler bit me hard enough to draw blood. I had asked the oncologist if it made sense to delay the scan because of the re-excision and he said not to worry because he’d know why there’s inflammation in that area. I’m thinking the bite and the shots will probably get flagged too. I just hope I don’t forget any other maladies or mishaps that might get flagged that I can’t explain.

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How often are they finding actual positive hits on the PET? If its so unreliably with regards to false positives why do you continue to have PET scans done?

PET Scans feature areas with blood flow so tumors show up as hot spots for follow up. People who are maybe only feeling off or had one confirmed tumor can have a lot of small tumors spread across their body which will show up clearly on a PET scan.

When my brother was at the end of his run fighting cancer he felt a bit under the weather and managed to catch covid so everyone figured he was feeling bad due to that. The PET scan showed he had thousands of small masses converging into the large mass that eventually killed him by cutting off blood flow to his kidneys. His cancer was an aggressive blood cancer that had stood up to conventional and Trial Chemo drugs. There was no way to treat this but other cancers that are less aggressive can be treated at this point and would be treated differently than a single mass.

In a nutshell it’s that level of visibility that makes PET scans worth it.

PET scans are not really unreliable, they’re just very sensitive and lots of anomalies ranging from benign cysts to malignant tumors show up on them. It’s not always possible to differentiate them without other measures like biopsies, so that’s where the false positives come in.

Getting regular scans to track cancer progression is a different matter altogether, since most of the blips can be eliminated over time and there’s a history to compare against.

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