Survivorship patterns of histopathological variants and molecular subtypes of breast cancer in a teaching hospital in Nigeria

Abstract

Objective : To study the relationship of histopathological characteristics, molecular subtypes of breast cancer and survival in a low resource setting. Design : Tumours from prospectively ascertained patients newly diagnosed with breast cancer were analyzed. Formalin-fixed and paraffin-embedded sections were constructed into tissue micro-arrays and immunostained with five anti-bodies. Five molecular subtypes were determined. Settings : The study was conducted jointly in the Department of Pathology of University of Ilorin Teaching Hospital, Ilorin in Nigeria and at the University of Chicago in the United States. Subjects : The study included a total of 203 histologically confirmed breast cancer patients whose pathological specimens were processed in the Department of Pathology of University of Ilorin Teaching Hospital, Ilorin, Nigeria between January 2003 and December 2007. Results : Mean age at diagnosis was 49.2 (SO ±11.9) years. Median time from symptom onset to cancer diagnosis was six months. Median follow-up time was 8.3 months. Median tumour size at diagnosis was 6cm. The proportion of ER+, PR+, HER2+ tumours were 27%, 16% and 30%, respectively. The most common molecular subtype was basal-like (25.1%) followed by unclassified (24.0%), luminal A (20.5%), HER2+/ER( 19.3%) and luminal B (11.1 %). Luminal A and B had best prognosis while basal-like and unclassified had worst prognosis. ER+ patients had longer duration of symptoms to diagnosis (median 8 months) than ER- patients (5 months) but ER+ patients had smaller tumours (median 5cm) than ER-patients (6cm, p=0.02). Recurrence-free survival was best for stage 1 and worst for stage 4 tumours. About 32.6% of patients had locoregional and/or metastatic recurrence. Conclusions : In consecutive breast cancer cases in Nigeria, almost half of patients were triple negative. Luminal A and B subtypes had best prognosis while triple negative had worst prognosis. The delay in breast cancer diagnosis and higher proportion of late stage of breast cancer underscores need for prompt diagnosis and initiation of treatment, especially hormonal therapy for ER positive patients.