Epidemiologic evidence of slow growing, nonprogressive or regressive breast cancer: A systematic review

The general aim of this systematic review is to mitigate breast cancer (BC) overdiagnosis and overtreatment. The specific aim is to summarize available data on the occurrence and features of indolent invasive or in situ (DCIS) BC, and precisely survival of untreated cases, prevalence of occult cancers found in autopsies, frequency of regressive BC. PubMed, Embase and Cochrane Library were systematically searched up to 3/31/2014. Eligibility criteria were: cohort studies, case-control studies, uncontrolled case series assessing survival in women with a diagnosis of BC who did not receive treatment compared to treated women; case series of autopsies estimating the prevalence of undiagnosed BC; cohort studies, case-control studies, uncontrolled case series, case reports assessing the occurrence of spontaneous regression of BC in women with a confirmed histology diagnosis. Untreated BC: 8 cohort studies and 12 case series (3593 BC) were included. In three controlled cohort studies (diagnoses 1978-2006), the 5-years overall survival was 19-43%. Occult BC: 8 case series (2279 autopsies) were included. The prevalence of invasive BC undiagnosed during lifetime range was 0-1.5%, while for DCIS the range was 0.2-14.7%. Spontaneous regression: 2 cohort studies, 3 case reports, 1 case series included. In the cohort studies the relative risk of regression for screen detected compared with nonscreened BC was estimated as 1.2 and 1.1. It seems plausible that around 10% of invasive BC are not symptomatic during life, and that one fith of BC patients if untreated would be alive after 5 years. Around 1 of 10 screen-detected BC may regress according two studies.