[robotrout]

    Welch says, "but [can also] find cancers that were never 
    going to matter."  That's because some cancers grow 
    slowly and never become dangerous, he says. 

This exact same phenomenon is already occurring with breast cancer. Everybody is a "breast cancer survivor" these days, because they keep finding these turtle tumors that were never going to be a problem. If you look at mortality rates between those who screen early and those who don't, they are the same.

https://link.springer.com/article/10.1007/s10549-018-4691-4

[1e-9]

While it is true that there is plenty of uncertainty regarding the value of finding DCIS, it is well established that there is significant benefit to finding small invasive breast cancers such as invasive lobular carcinoma and invasive ductal carcinoma. The value is particularly significant if the lesions are found before exceeding 1 cm in size, which they often are nowadays. The paper sited refers to one study focused on DCIS and another Canadian study on breast cancer screening during the 1980's and 1990's before there were good mammography screening standards. The Canadian study essentially just showed that poor screening is of limited value.