Risk of Invasive Breast Cancer Similar With Family History of In Situ or Invasive Disease

By Marilynn Larkin

November 19, 2020

NEW YORK (Reuters Health) - Women had similar risks for invasive breast cancer whether they had a family history of the same condition or of breast carcinoma in situ, a Swedish cohort study found.

The findings should be considered practice-changing, and guidelines should change, according to Dr. Mahdi Fallah and Dr. Elham Kharazmi, both of the German Cancer Research Center and the National Center for Tumor Disease in Heidelberg. "This study identified a new high-risk group - i.e., women with family history of breast carcinoma in situ, who need similar attention to those with family history of invasive breast cancer," they said.

In 2019, their team published risk-adapted starting ages of screening for women with a family history of invasive breast cancer (https://bit.ly/38OQ7Ao). "We advise clinicians to follow that guidance also in case of family history of breast carcinoma in situ," adding a year or two to the starting age for screening, based on recent risk calculations, they said.

For a new study reported in BMC Medicine, the team analyzed cancer occurrence in more than five million Swedish women born after 1931. Registry data were collected from 1958-2015.

Most of the women (87.6%) did not have a family history of breast cancer in first- and second-degree relatives. Among 40,352 women with a family history of only breast carcinoma in situ, 584 developed invasive breast cancer during follow-up.

Having one first-degree relative with breast carcinoma in situ was associated with a 50% increased risk of invasive breast cancer (standardized infection ratio, 1.5) compared to those with no family history in either first- or second-degree relatives.

Similarly, having one first-degree relative with invasive breast cancer was associated with a 70% (1.7) increased risk.

Further, women who had only a second-degree relative with breast carcinoma in situ were at a 20% increased risk, whereas the risk increased 30% when a second-degree relative had invasive breast cancer.

Similar risks were seen for women with in situ disease who had either two second-degree relatives with invasive disease (1.6) or one first-degree relative with in situ disease (1.5).

The 10-year cumulative risk at age 50 for women with a relative with breast carcinoma in situ was 3.5%; this was not significantly different from the 3.7% risk for 50-year-old women with a relative with invasive breast cancer.

However, significant differences were seen in the 10-year cumulative risk for younger women with a family history of in situ or invasive breast cancer. For example, at age 30, the 10-year cumulative risk of breast cancer for a woman with family history of breast carcinoma in situ in a first-degree relative was 0.2%; however, the risk was 0.6% for women with a family history of invasive breast cancer in a first-degree relative.

Surgical oncologist Dr. Stephen Edge, Vice President of Healthcare Outcomes and Policy at Roswell Park Comprehensive Cancer Center in Buffalo, New York, told Reuters Health, "The results are compelling. Further, the finding agrees with most experts' understanding that a family history of ductal carcinoma in situ should be included in defining an individual's breast cancer risk and determining the chance of harboring a breast cancer-related gene mutation."

"The National Comprehensive Cancer Network Guidelines for Genetic/Familial High-Risk Assessment already include the recommendation that family history of both invasive cancer and ductal carcinoma in situ be included in assessing risk and defining testing criteria for genetic testing," he said by email. "Other guidelines are largely silent on this issue, largely because it is not clear that these data were collected in the studies, often done many years ago, on which (the guidelines) are based."

"The finding in this and other reports should be made available to women with a family history and used in calculating breast cancer risk," he said.

"However," he added, "many women will report a family history of breast cancer and not be aware of any distinction between ductal carcinoma in situ and invasive cancer. They may not (know) which (condition) their relative had."

SOURCE: https://bit.ly/2K9uqR3 BMC Medicine, online November 5, 2020.

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