DCIS: many breast ‘cancers’ behave benignly – e.g. some 94% survival at 20 years after diagnosis with no symptoms https://jamanetwork.com/journals/jamaoncology/fullarticle/2634502

before breast cancer screening only a few percent of all breast cancers diagnosed were DICS

after screening introduced – 20-25% of all breast cancers classed as DCIS https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/441318/nhsbsp66.pdf

very little known about natural history of these types of abnormality before breast screening – mainly women who had been diagnosed and then lost to follow up 

but hardly any seemed to spread quickly and behave like we think cancers should 

https://www.bmj.com/content/361/bmj.k1410 https://scienceblog.cancerresearchuk.org/2017/05/24/preventing-unnecessary-breast-cancer-treatment/

https://www.sciencedirect.com/science/article/pii/S096097761630162X

less than 1% of DCIS patients will go on to develop invasive breast cancer annually. 

trials due to report https://www.pcori.org/research-results/2015/comparing-benefits-and-harms-watchful-waiting-versus-standard-treatment-women

some have suggested renaming e.g. DCIS as indolent lesions of epithelial origin” (IDLE)

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4322920/

study in lancet oncology published 2014

– no lower threshold 

https://www.thelancet.com/journals/lanonc/article/PIIS1470-2045(13)70588-6/fulltext