How effective is surgical treatment for ductal carcinoma in situ (DCIS) at preventing an invasive recurrence of breast cancer? Treatment is intended to significantly lessen the lifetime risk of breast cancer and breast cancer-related mortality, but are patients diagnosed with DCIS still at risk for experiencing poor outcomes?

A recent study in JAMA Network Open examined a number of patients diagnosed with DCIS who underwent surgical treatment with the intent of comparing their risk of breast cancer and related mortality with those without a similar diagnosis. What the researchers found was that the risk of breast cancer mortality in the 20 years after a DCIS diagnosis could be greater than anticipated compared with the risk in those without one.

The researchers pulled data from the Surveillance, Epidemiology and End Results (SEER) registries database. Using this publicly available information (a database in which participants were deidentified), the researchers examined information from 144,524 women with DCIS from 1995 to 2014. Patients with a diagnosis of carcinoma in situ without evidence of an invasive component were included in the study; exclusion criteria included microinvasion, lobular carcinoma in situ, nonepithelial histological presentations, Paget disease of the nipple, or diffuse DCIS. All of these women underwent surgical treatment for DCIS, and 68,118 also received radiotherapy. The women were followed until December 31, 2016, unless they died (either of breast cancer or an unrelated cause), were lost to follow-up, or 20 years had passed since the initial diagnosis of DCIS.

The researchers used breast cancer incidence rates specific to the ages and years of the study to calculate an estimated  458.6 breast cancer deaths from the 144,524 patients. However, they observed 1540 breast cancer deaths in this cohort, which was more than 3 times the expected likelihood.


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This ratio was similar when broken down across different eras. From 1995 to 1999, the data showed 426 observed deaths vs 129.5 expected deaths, while from 2005 to 2009 it showed 343 observed deaths vs 104 expected deaths. These are observed-to-expected ratios of approximately 3.29 and 3.3, respectively.

Age and race were also factors where observed deaths were significantly higher than expected ones. Among women who received a DCIS diagnosis at an age younger than 49, the researchers observed 92 deaths, which was nearly 12 times more than the 8.2 expected breast cancer deaths. Of the women observed, 15,415 were Black. This demographic had 319 observed deaths compared with 42.2 expected, which was more than 7.5 times greater. When focused on Black women younger than 40 (692), the number of observed breast cancer deaths was more than 22 times greater than expected.

The researchers observed 238 breast cancer deaths from the 17,313 women who underwent unilateral mastectomy for DCIS compared with 57.8 breast cancer deaths expected deaths. Of the 63,827 women who underwent lumpectomy plus additional radiotherapy, 496 deaths were observed compared with an expected 176.7.

The researchers acknowledge limitations of the study and note that the 3% lifetime risk of breast cancer death following DCIS is not enough to recommend chemotherapy. However, there is value to knowing that women may be at greater risk for breast cancer mortality after surgical treatment for DCIS than was initially anticipated, as well as knowing that race may place women at an even greater risk.

Reference

Giannakeas V, Sopik V, Narod SA. Association of a diagnosis of ductal carcinoma In situ with death from breast cancer. JAMA Netw Open. 2020;3(9):e2017124. doi:10.1001/jamanetworkopen.2020.17124