That was the conventional wisdom for years and it seems obviously true - catch cancer early before it spreads. Yet when we actually study these things we find

That was the conventional wisdom for years and it seems obviously true - catch cancer early before it spreads. Yet when we actually study these things we find out early detection might not be desirable (but also sometimes is). It's complicated and there's a whole lot we don't know. Also "most cancers" is almost certainly false, more like "some cancers." And at what cost? https://fivethirtyeight.com/features/the-case-against-early-cancer-detection/ https://fivethirtyeight.com/features/the-case-against-early-... >It’s hard to believe in overdiagnosis and overtreatment if you imagine that cancer behaves in a progressive manner: that is, that it arises from one haywire cell that replicates abnormally before inevitably spreading to other parts of the body, eventually killing the person. Let’s call this way of thinking the relentless progression model. In this model, every cancer cell is destined to spread and become lethal, and that’s how doctors have traditionally been taught to think of cancer’s progression. >Today, thanks to sophisticated cancer genetics and advances in tumor biology, we know that’s not always how it works. Cancer is not a single disease; it’s many. On one end of the spectrum lie cancers that become aggressive and invasive from the start, and on the other end are cancers that remain non-invasive and therefore harmless. Whether a single rogue cell replicates slowly and stays put or goes wild and spreads is determined by a variety of factors that scientists are still working to understand. >What’s clear is that cancers fall into a few general behavior patterns, which Welch and others have compared to animals that must be kept in the barnyard to prevent a deadly rampage. Papillary tumors are like turtles — they move very slowly and never pose an escape risk. They don’t need screening, because they will never cause trouble. Then there are rabbits, which are eager to hop away to other parts of the body, but can be confined if they’re found and fenced. These are the cancers that can be helped by early detection and treatment. Birds, on the other hand, are so flighty and quick that they can’t be confined. Screening makes no difference for bird cancers, because they’re so aggressive that they can’t be detected before they’ve begun their deadly course. >No cancer screening has ever eliminated the majority of cancer deaths. Instead, the best screening can do is reign in the rabbits. Birds remain unstoppable, and they’re the ones responsible for most cancer deaths. This is why, Welch says, three decades of mammography have failed to put a dent in the rate of women presenting with metastatic breast cancer upon their initial diagnosis. See also: https://sciencebasedmedicine.org/a-skeptical-look-at-screening-tests/ https://sciencebasedmedicine.org/a-skeptical-look-at-screeni... https://www.wbur.org/commonhealth/2017/06/08/cancer-diagnosis-wealthy https://www.wbur.org/commonhealth/2017/06/08/cancer-diagnosi...