Young Women With No Genetic Mutations Have Low Risk of Second Primary Breast Cancer
If a woman is diagnosed with breast cancer at age 40 or younger, she has a low risk of developing a second primary breast cancer, unless she has a genetic mutation linked to breast cancer, such as BRCA1 or BRCA2, according to a study published on April 11, 2024, by the journal JAMA Oncology.
Key takeaways
Among women diagnosed with a first breast cancer at age 40 or younger, the risk of developing a second primary breast cancer in the 10 years after diagnosis was about 2% in the 544 women in the study who didn’t have a genetic mutation linked to breast cancer.
Among the 33 women in the study who were also diagnosed at age 40 or younger and did have a mutation linked to breast cancer, the risk of a second primary breast cancer was about 9%.
What the results mean for you
This study shows that young women have a low risk of developing a second breast cancer, unless they have a genetic mutation linked to breast cancer.
The likelihood of having a BRCA mutation is low for most people. But if you’ve been diagnosed with breast cancer before age 40, it’s critical to have genetic testing to figure out your risk of a second cancer as precisely as possible. Once you have this information, you and your doctor can discuss the best treatment options for your unique situation, taking into account your personal preferences and health history.
The results from this study refute previous assumptions about risk. Studies done in 2019 and 2021 suggested that the risk of a second primary breast cancer was two to three times higher in women who are younger than 40 when they’re first diagnosed with breast cancer than it is for women who were older when diagnosed.
Because of this, many young women opt to have mastectomy instead of lumpectomy, and also have the other, unaffected breast removed — called prophylactic mastectomy — to reduce the risk of a second breast cancer.
But those earlier studies didn’t separate out women who had a genetic mutation. So it’s likely that they overestimated the risk in women without a genetic mutation and underestimated the risk in women who had a genetic mutation.
About the study
This analysis looked at information from 685 women diagnosed with stage 0 to stage III breast cancer.
Among the 685 women:
577 women had genetic testing, and 33 (6%) had a genetic mutation linked to breast cancer; 24 of these women had a BRCA1 or BRCA2 mutation
average age at diagnosis was 36
82% were white
The researchers followed the women for seven to 12 years.
Detailed results
During follow-up, 17 of the 685 women (2.5%) developed a second primary breast cancer. These were diagnosed 3.3 to 5.6 years after the initial cancer.
Two of the second primary cancers were in the same breast as the first cancer, and 15 were in the opposite breast.
The risk of second primary breast cancer in the five and 10 years after initial diagnosis was higher in women who had a genetic mutation linked to breast cancer.
Five-year risk was:
5.5% in women with a mutation
1.3% in women without a mutation
Ten-year risk was:
8.9% in women with a mutation
2.2% in women without a mutation
The researchers said the findings show how important genetic testing is for young women who’ve been diagnosed with breast cancer.
“The results of this cohort study suggest a relatively low five- and 10-year cumulative incidence of second primary breast cancer among patients aged 40 years or younger with breast cancer who are non-carriers of pathogenic variants, emphasizing the importance of genetic testing among patients with breast cancer,” the researchers wrote. There’s room for improvement here, they explain, given the low rates of genetic testing among women recently diagnosed with breast cancer.
Brantley KD, Rosenberg SM, Collins LC, et al. Second Primary Breast Cancer in Young Breast Cancer Survivors. JAMA Oncol. Published online April 11, 2024.
Updated on August 31, 2024