DCIS linked to three fold increase in death risk in breast cancer: JAMA study

Researchers have found in a new study that the risk of dying of breast cancer was increased 3-fold after a diagnosis of Ductal carcinoma in situ (DCIS) in women compared to those in the general population. The study was published in the journal "JAMA Network Open" 2020.

Ductal carcinoma in situ (DCIS), generally seen in asymptomatic women, refers to the histological appearance of cancer cells within the breast ductule/lobule without evidence of cancer cells present beyond the basement membrane. Even though it is not life-threatening it can progress to breast cancer in the future. There are little evidence and no clarity on what extent a diagnosis of ductal carcinoma in situ (DCIS) impacts a woman's lifetime risk of dying of breast cancer. Hence researchers from Toronto, Canada conducted a study to determine the risk of death from breast cancer in a large cohort of patients treated for DCIS and to compare the risk with that of women in the general population.

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The authors conducted a cohort study by including data for women who had the first primary DCIS diagnosed between 1995 and 2014 from the Surveillance, Epidemiology, and End Results (SEER) registries database. They were followed up till 2016. Women with diagnosed DCIS were treated surgically, and nearly half of the patients also received radiotherapy, and women without breast cancer were taken as a control population. Follow up of these patients was done from the date of DCIS diagnosis until death from breast cancer or the date of the last follow-up.

The main outcome of measurement was death due to breast cancer. Standardized mortality ratios were estimated by comparing deaths and the expected probability of death from breast cancer in the general population was calculated by an incidence-based mortality approach. The probability of breast cancer death was estimated by studying women diagnosed with DCIS and following her till the end of follow up.

The key findings of the study were:

• A total of 144 524 women diagnosed with first primary DCIS were included with a mean [SD] age at diagnosis being 57.4 [11.0] years.

• There were 1540 deaths from breast cancer in the cohort.

• Based on SEER-based incidence and case-fatality rates, 458 breast cancer deaths were expected in an equivalent number of cancer-free women from the general population with equal follow-up.

• The standardized mortality ratio for death from breast cancer among women with DCIS was 3.36.

• The elevated risk of death persisted more than 15 years after diagnosis.

Thus, the researchers concluded that the risk of dying of breast cancer was increased 3-fold after a diagnosis of DCIS. They also suggested that the current treatment focus on preventing invasive recurrence is insufficient to eliminate all deaths from breast cancer after DCIS. 

To read more, click the following link: 10.1001/jamanetworkopen.2020.17124