Comparative Survival Analysis of HER2-Positive Pregnancy-Associated Breast Cancer and Non-Pregnant Cohorts: A matched control study

Purpose : This retrospective matched cohort single-center study focused on comparing prognosis between HER2-positive PABC and non-pregnant individuals with HER2-positive breast cancer. Methods: Clinical and histopathological data were collected from a prospectively maintained patient database at King Hussein Cancer Center, a tertiary cancer-care center in Jordan. The study analyzed overall survival (OS), recurrence-free survival (RFS), and event-free survival (EFS) in HER2-positive PABC matched 1:1 to non-pregnant patients with HER2-positive breast cancer (non-PABC). Results : The analysis encompassed 128 patients, divided into two main groups: 64 patients diagnosed with PABC and 64 patients classified as non-PABC cases. Although there was not a statistically significant difference in OS between non-pregnant and pregnant individuals (p=0.12), it was notable that pregnant individuals experienced a significant delay in the initiation of anti-HER2 treatment (23.8± 19.3 weeks, p= 0.02). Additionally, there was a higher risk of recurrence or events in pregnant individuals, emphasizing the potential impact of pregnancy on these survival outcomes (HR=1.93, p=0.029 and HR=2.00, p=0.02, respectively). Furthermore, PABC individuals who completed the 12-months of anti-HER2 treatment were comparable to non-PABC individuals who completed the same treatment (p=0.3), while incomplete treatment significantly affected survival outcomes (HR=4.94, 95% CI: 1.41 to 17.3, p=0.012). Conclusion: Despite a notable delay in the initiation of anti-HER2 treatment in PABC patients compared to non-PABC cases, both cohorts exhibited similar prognostic outcomes in terms of overall survival when anti-HER2 treatment has been completed. This discovery emphasizes the importance of promptly initiating and completing anti-HER2 treatment in pregnant individuals to optimize prognosis.