Population-based Study of Factors Influencing Invasive Breast Cancer Risk after Screen-detected Ductal Carcinoma in Situ: First results from the Non-Invasive Breast Cancer in England (NINBE) Study
Session type: Poster / e-Poster / Silent Theatre session
Theme: Epidemiology and prevention
Ductal carcinoma in situ (DCIS) is the commonest non-invasive breast cancer and accounts for one fifth of all screen-detected breast cancers. DCIS may develop into invasive breast cancer (IBC) if untreated but, even when treatment has been given, its prognosis remains uncertain, as does the optimal level of treatment. We aimed to quantify the risk of IBC amongst women with screen-detected DCIS in England and to examine the factors associated with this risk.
We undertook a cohort study using data from the National Health Service Breast Screening Programme Audit and Public Health England’s Cancer Analysis System. We included all women diagnosed with DCIS during 1/1/2000–31/12/2015 in England. Women with a prior diagnosis of any invasive cancer, except non-melanoma skin cancer, were excluded. Women were followed from the date of their DCIS diagnosis to the earliest of IBC diagnosis, death, loss to follow-up, or 31/12/2015.
30,269 women were diagnosed with screen-detected DCIS and 1,491 (4.9%) were subsequently diagnosed with IBC. The cumulative risks of IBC at 5, 10 and 15 years after DCIS diagnosis were 3.5%, 7.5%, and 10.1% respectively. Women with clear surgical margins of 1–2 mm had a higher IBC rate than women with clear margins of 10+ mm (RR 1.60, 95% CI 1.20–2.13). Women given breast-conserving surgery without radiotherapy had a higher IBC rate than women given mastectomy (RR 1.48, 95% CI 1.29–1.71). Women given tamoxifen had a lower rate of subsequent IBC compared with oestrogen receptor (ER) positive women not given tamoxifen (RR 0.74, 95% CI 0.65–0.86). IBC rate did not vary significantly by age at diagnosis, pathological grade or ER status.
Our study is the largest of its kind in the UK. It is starting to shed new light on the prognosis of screen-detected DCIS under various management options.