Retrospective assessment of Duffy-Null associated neutrophil counts (DANC) status and impact on treatment among patients with and without cancer in an urban academic medical center.

1642 Background: Duffy-Null Associated Neutrophil Count (DANC) is a non-pathologic state characterized by a low absolute neutrophil count (ANC) without increased risk of infections. Despite this, cancer patients (pts) with DANC have often been excluded from clinical trials due to low ANC and may receive inappropriate dose delays or reductions of standard anticancer therapy. Testing for Duffy-null phenotype is readily available, but no standard of care exists for management of chemotherapy dosing in cancer pts with DANC. In preparation for a prospective study evaluating chemotherapy dose modifications in cancer pts with DANC, we examined characteristics of pts, both with and without cancer, who underwent Duffy antigen testing at our institution, as well as whether results of testing in cancer pts impacted cancer management. Methods: Pts who received Duffy antigen testing from 05/02/2024-05/01/2025 were identified from the Montefiore Health System pt registry. Baseline characteristics including white blood cell count (WBC), ANC, demographics, and cancer status were obtained and correlated with Duffy status. Reviewed documentation for Duffy-status impact on chemotherapeutic management. Results: 523 pts [283 (54.1%) Non-Hispanic Black (NHB), 168 (32.1%) Hispanic (H), 18 (3.4%) Non-Hispanic White (NHW), and 54 (10.3%) Other] were identified. Median age was 56 yrs. Indication for testing was neutropenia in 518 pts (99.0%). 407 (77.8%) pts were found to have DANC and 116 (22.2%) were Duffy-antigen positive. Duffy-null phenotype was seen in 265 (93.6%) pts; 103 (61.3%) H pts, and 4 (22.2%) NHW pts. Race/ethnicity was strongly correlated with Duffy-status (p < 0.001). Median baseline WBC and ANC were lower in pts with DANC than in pts without [WBC 3.4 vs 4,4 (p < 0.001); ANC 1.1 vs 1.8 (p < 0.001)]. 32 (6.4%) pts of the total cohort had cancer [23 (71.9%) NHB, 7 (21.9) H, 2 (6.3%) other], of which 26 pts (22 NHB, 4 H) had DANC. 13 (40.6%) ordering providers were adult solid tumor oncologists [8 Breast, 4 GYN, 1 GU], 5 (15.4%) pediatric hematologist-oncologists, 6 (18.8%) classical hematologists, 6 (18.8%) hematology/oncology providers, and 2 (6.3%) family medicine providers. Knowledge of Duffy antigen status impacted management in 26 (81.3%) pts with cancer, leading to fewer dose delays and reductions in cancer pts with DANC, while in 6 (18.8%) pts testing did not (p = 0.31). Conclusions: In our diverse cohort of pts undergoing Duffy antigen testing, predominantly as part of evaluation for neutropenia, almost all NHB pts were found to have Duffy-null phenotype. DANC was also seen in over half of H pts, and in 22% of NHW pts. Among cancer pts, testing for DANC is underutilized, but frequently impacts chemotherapy management, emphasizing the need for prospective evaluation of the utility of Duffy antigen testing in cancer pts receiving chemotherapy.