Differential Second Primary Malignancy Occurrence After Breast Cancer According to HER2 Status: A Population-Based...

Area of Science:

• Oncology
• Cancer Epidemiology
• Biomarker Research

Background:

• Human Epidermal growth factor Receptor 2 (HER2) is a key biomarker in breast cancer (BC).
• Understanding the association between HER2 status and the risk of second primary malignancies (SPMs) is crucial for patient management and prognosis.

Purpose of the Study:

• To investigate the association between HER2 status in breast cancer patients and the subsequent occurrence of second primary malignancies (SPMs).

Main Methods:

• Utilized the NCI SEER database (2010-2018) for 409,796 first primary breast cancer patients.
• Employed standardized incidence ratio (SIR), Poisson regression, cumulative incidence functions, Gray's test, and proportional subdistribution hazards regression.
• Adjusted for competing risks of death in the analysis.

Main Results:

• HER2-positive (HER2+) BC patients exhibited a significantly lower incidence of SPMs compared to HER2-negative (HER2-) BC patients (SIR 1.03 vs 1.13).
• The risk reduction for SPMs was particularly notable for second primary breast cancer (RR 0.89) and lung cancer (RR 0.84).
• Five-year cumulative incidence of SPM was lower in HER2+ BC patients (4.09%) versus HER2- BC patients (5.16%); HER2 positivity also correlated with better overall survival among SPM patients.

Conclusions:

• HER2-positive breast cancer is associated with a significantly lower incidence of second primary malignancies.
• This protective effect is most pronounced for the development of subsequent breast cancer and lung cancer.
• HER2 status may serve as a prognostic factor for SPM risk and survival outcomes in breast cancer patients.