BACKGROUND: Breast cancer remains to be the leading cause of malignancy among women and survival rates vary worldwide. Molecular and immunohistochemical (NC) profiling of breast cancer has emerged to improve treatment, which led to 6 different breast cancer subtypes luminal-A, luminal-B, Her-2 enriched, basal-like, daudin low, and normal breast. Essentially, this guides clinicians as to the choice of treatment and prognostication of disease. This study evaluates the characteristics of the different IHC subtypes of breast cancer among Filipinos as to pattern of recurrence and time to progression (TIP) within their 1st 2 years of follow-up.
METHODS: This is a retrospective cohort study, approved by the University of the Philippines Manila Research Ethics Board (UPMREB). Study population included breast cancer patients enrolled in the DOH-BCMAP and managed at the medical oncology clinics of the Philippine General Hospital (PGH) and Jose R. Reyes Memorial Medical Center (JRRMMC) from 1 May 2011 to 31 December 2013. Patients' demographics, disease and treatment profile were gathered from the medical charts. Patients were grouped into 12 different IHC subtypes utilizing only IHC staining results of Her2neu, ER and PR. Disease progression/ relapse and time to progression (UP) were primary outcomes analyzed and compared between subtypes using SPSS.
RESULTS: There were 368 eligible patients; 50% were >50 years old, 48% postmenopausal, 34% stage IIA, and 94% had invasive ductal carcinoma. About 88% completed their chemotherapy regimen, mostly AC-T. At 1 to 2 years follow-up, 18% had disease progression, mostly distant metastasis, with HER2neu(-)/ER(-)/PR(-), HER2(+), and HER2neu(-)/ER(+)/PR(+) subtypes having the most number of disease progression. The HER2neu(-)/ER(-)/PR(-) subtype had the shortest median TTP (11 months 9sd). HER2(+) subtype had median TTP of 14±8 sd, while HER2neu(-)/ER(+)/PR(+) had median TTP at 11.6±7.41 sd. The median TTPs among the different IHC subtypes were statistically comparable.
CONCLUSION: Filipinas with non-metastatic breast cancer after surgery and mainly on adjuvant chemotherapy started to develop disease progression/ relapse within the first 2 years of follow-up; 82% had no relapse. At these early years of follow-up, the median TTPs among the different breast cancer IHC subtypes who went into relapse were comparable, although HER2neu(+) regardless of ER/PR subtype tended to have more disease progression, followed by HER2neu(-)/ ER(-)/ regardless of PR subtype, and then HER2neu(-)/ ER(+)/ regardless of PR subtype. IHC resultant HER2neu(+) regardless of ER/PR and HER2neu(-)/ER(-)/PR(-/+) subtypes can serve as early prognosticators of breast cancer relapse.