Clinical Implications and Prevalence of Duffy-Null Associated Neutrophil Count in Patients With Breast Cancer of Middle Eastern Ethnicity

Duffy-null associated neutrophil count (DANC), formerly known as benign ethnic neutropenia, is seen in people of African and Middle Eastern descent and does not represent a true neutropenic state. Individuals with DANC can be identified by the Duffy-null phenotype on red cells. There is evidence that cancer patients with DANC are not at an increased risk of infection with chemotherapy. The aims of this study were to assess the prevalence of DANC among patients with breast cancer of Middle Eastern ethnicity and to study treatment delays, infectious complications, and survival in these patients.

We retrospectively reviewed 493 patients with breast cancer treated in a referral oncology center in Bahrain. Patients with neutropenia or leukopenia at presentation with Duffy-null phenotype and no identifiable secondary causes of neutropenia were presumed to have DANC. Clinical details studied included treatment delays, filgrastim responsiveness, and episodes of febrile neutropenia. A contemporaneous group of patients with breast cancer without DANC were used for comparison.

Seventy-two patients (14.6%) had a presumed diagnosis of DANC, and the median neutrophil count at presentation was 1.2 × 10³/µL (range, 0.4-2.1 × 10³/µL). Treatment delays and discontinuations were significantly more common in patients with DANC (P < .001) and were not decreased by prophylactic filgrastim use. Patients with DANC were uniformly filgrastim responsive, and only one patient had neutropenic fever. There was no effect of treatment delay or DANC on OS or PFS.

DANC is prevalent among patients with breast cancer in Bahrain, and Duffy phenotyping on red cells can be a surrogate marker for diagnosis. Treatment delays because of the apparent neutropenia are common in DANC; however, febrile neutropenia is uncommon. This study is of particular relevance in populations with a high prevalence of DANC.