Impact of microinvasion on breast cancer mortality in women with ductal carcinoma in situ

Ductal carcinoma in situ (DCIS) is a neoplastic proliferation of epithelial cells which is confined within the basement membrane of the mammary ductal–lobular system. It is of interest to determine to what extent the potential to metastasize increases for DCIS patients when the basement membrane is breached (i.e. microinvasion is present).

We retrieved the records of 525,395 women who had either first primary DCIS or small (≤ 2.0 cm) node-negative invasive breast cancer in the Surveillance, Epidemiology and End Results (SEER) registries database (1990–2013). For each patient, we extracted information on year of diagnosis, age at diagnosis, tumour size, tumour grade, oestrogen receptor status, use of radiotherapy, type of surgery, cause of death and follow-up time. We classified patients into four groups, according to the size of the invasive component of the primary tumour. We estimated the actuarial rate of breast cancer-specific mortality at ten and 20 years for women in each size category.

In terms of prognosis, microinvasive cancer more closely resembles small invasive cancer 0.2–1.0 cm) than pure DCIS. For invasive cancers under 1.0 cm, size has little impact on mortality.