Certain Women May Face Higher Risk for Second Breast Cancer

TOPLINE:

A recent study suggests that younger breast cancer survivors with a germline pathogenic variant or those with an initial diagnosis of in situ vs invasive primary breast cancer have a significantly higher risk for a second primary breast cancer.

METHODOLOGY:

• Women who are diagnosed with breast cancer at age 40 or younger are about two to three times more likely to develop second primary breast cancer compared with women who are older when first diagnosed.
• However, data are lacking on whether certain factors increase a woman’s risk for a second primary breast cancer.
• To classify the risk of developing a second primary breast cancer, the researchers evaluated a main cohort of 685 patients with stages 0-III breast cancer who were diagnosed at age 40 years or younger and had undergone unilateral mastectomy or lumpectomy as primary surgery between August 2006 and June 2015. The team also analyzed data on 547 younger women who had a bilateral mastectomy.
• The researchers assessed various breast cancer risk factors, including self-reported ethnicity, race, age, family history of breast or ovarian cancer, germline genetics, tumor stage, grade, and receptor status.
• The primary outcome was the diagnosis of a second primary breast cancer that occurred at least 6 months after the initial diagnosis of primary breast cancer.

TAKEAWAY:

• Among the 685 main study participants, 17 (2.5%) developed a second primary breast cancer (15 contralateral and 2 ipsilateral) over a median of 4.2 years since their primary diagnosis. The 5- and 10-year cumulative incidence of a second primary breast cancer was 1.5% and 2.6%, respectively.
• Overall, only 33 women were positive for a germline pathogenic variant, and having a pathogenic variant was associated with a fourfold higher risk for second primary breast cancer compared with noncarriers at 5 years (5.5% vs 1.3%) and at 10 years (8.9% vs 2.2%). These findings were held in multivariate models.
• Patients initially diagnosed with in situ disease had more than a fivefold higher risk for second primary breast cancer compared with those initially diagnosed with invasive disease — 6.2% vs 1.2% at 5 years and 10.4% vs 2.1% at 10 years (hazard ratio, 5.25; P = .004). These findings were held in multivariate models (adjusted sub-hazard ratio [sHR], 5.61; 95% CI, 1.52-20.70) and among women without a pathogenic variant (adjusted sHR, 5.67; 95% CI, 1.54-20.90).
• The researchers also found a low risk for contralateral breast cancer among women without pathogenic variants, which could inform surgical decision-making.

IN PRACTICE:

Although the number of women positive for a germline pathogenic variant was small (n = 33) and “results should be interpreted cautiously,” the analysis signals “the importance of genetic testing” in younger breast cancer survivors to gauge their risk for a second primary breast cancer, the authors concluded. The authors added that their “finding of a higher risk of [second primary breast cancer] among those diagnosed with in situ primary [breast cancer] merits further investigation.”