Young breast cancer and the influence of ethnicity in Sandakan: A 3-year retrospective cross-sectional study.

Introduction: Breast cancer (BC) is the most common cancer in Malaysia, with incidence increasing with age. There have been demonstrated differences in age of presentation and tumour biology when comparing ethnicities. Twenty percent of Caucasian women present before 50 years old, but almost 50% of Southeast Asian (SEA) women present before 50. However, BC in Indigenous sub-groups has not yet been studied. Sandakan is a city in Sabah with a large Indigenous population. Current nationwide screening guidelines are based on the U.S. Preventive Task Force 2009 Guidelines, which may not represent our population. We aim to examine the age of incidence for our local population, for local screening recommendations.

Method: Retrospective cross-sectional study, including all consecutive cases of epithelial invasive tumours, from January 2016 to December 2018. Other histological types were excluded. Univariate and multivariate analyses were performed.

Result: A total of 115 breast tumours were identified. Ten tumours were excluded (five ductal carcinoma in situ, four phyllodes, and one sarcoma), leaving a study population of 105 patients. Median age of presentation was 53 years (min 30; max 97). A total of 41.9% presented before the age of 50. Patients of Indigenous ethnic origins were 11 years younger at presentation than non-Indigenous women. Tumour grade was more likely to be higher among Indigenous women.

Conclusion: Median age of presentation of BC in Sandakan matches regional data; however, patients of Indigenous ethnic groups present even earlier. Screening guidelines should consider the growing evidence of young BC in SEA.