The Duffy Null Phenotype — Addressing a Source of Discrimination in Cancer Care

Structural racism describes the barriers to equity built into myriad societal domains.It operates in health care by means of policies, practices, and systems, "affecting health in ways often more difficult to recognize than explicit interpersonal racism." 1 Efforts are under way to dismantle these mutually reinforcing structures in oncology.Cancer research and care practices that adversely affect people with the Duffy null phenotype, however, are an underrecognized and widespread source of discrimination against people of African or Arab ancestry.This erythrocytic phenotype, which is seen in approximately 67% of people who identify as African American, confers partial resistance to the malariacausing parasite Plasmodium vivax by limiting its ability to enter red cells. 2The Duffy null phenotype is also associated with a circulating absolute neutrophil count (ANC) that is approximately 40% lower than that in people without this phenotype, without conferring increased risks of infection or disease. 3Although this variant is common and its effect on the ANC is predictable, cancer research and care practices continue to discriminate against people with Duffy null-associated neutrophil count (DANC).Areas of discrimination include clinical trial eligibility criteria, adverse-event grading, dose modification for systemic anticancer therapy, and remission criteria (see table ).Recently, we found that about 77% of phase 3 clinical trials for the five most prevalent cancers in the United States and the United Kingdom had eligibility criteria that explicitly or implicitly excluded some patients with DANC. 4 The ANC reference range for people with the Duffy null phenotype is approximately 1200 to 5400 cells per microliter, 3 and about 10% of healthy people with this phenotype have an ANC of less than 1500 cells per microliter.