Impact of Iron Deficiency Anemia on Inpatient Mortality, Hospital Cost, and Length of Stay in Patients with Luminal Gastrointestinal Cancers: Data from the Healthcare Cost and Utilization Project from 1999-2014

Background: Anemia frequently complicates the course of cancer, varying widely depending on the cancer type and stage. Iron deficiency anemia (IDA), specifically, can develop in nearly half of this population1. The impact of iron deficiency anemia on prognosis in cancer patients is largely unknown. We endeavored to evaluate trends in the prevalence of IDA in relation to inpatient mortality, costs of hospitalization, and length of stay in patients admitted with luminal gastrointestinal cancers (esophageal, gastric, small intestine, and colorectal cancers for the purpose of this study).

Methods: We analyzed data from the Healthcare Cost and Utilization Project's (HCUP) National Inpatient Sample, between 1999 and 2014 using the ICD-9 codes for esophageal cancer (150), gastric cancer (151), small intestinal cancer (152.9, 209.0), and colorectal cancer (153.0, 153.1, 153.2, 153.3, 153.4, 153.6, 153.7, 153.8, 153.9, 154.0, 154.1) in the primary diagnosis field. The subset of these numbers with IDA (280.9) listed as a secondary diagnosis were recorded to derive a prevalence of iron deficiency anemia within this luminal gastrointestinal cancer population. The prevalence of iron deficiency anemia, inpatient mortality, total hospital cost, and length of stay (LOS) were compared among the luminal gastrointestinal cancers.

Results: A total of 588,142 (weighted N=2,896,663) admissions with a primary luminal gastrointestinal cancer diagnosis were identified from 1999-2014. A total of 30,566 (weighted N=150,961) admissions were associated iron deficiency anemia. A total of 557,576 (weighted N=2,746,257) admissions were not associated with anemia.

In patients with esophageal cancer and IDA, inpatient mortality was higher at 11.5%, compared to 4.7% in those without IDA (p< 0.0001). Overall hospital cost was higher at $64,140 (± 564) versus $52,692 (± 2430) (p< 0.0001). IDA was also associated with an increase in length of stay at 9.7 days compared to 8.9 days, though not significantly (p= 0.06). In gastric cancer patients with concurrent IDA, inpatient mortality was higher at 9.1% as compared to 3.8% in those without IDA (p< 0.0001). The total charges were higher with IDA: $66,179 (± 361) vs. $59,745 (± 1325) (p< 0.0001). Gastric cancer patients with IDA also had a longer length of stay of 10.3 days in comparison to 9.4 days in those without IDA (p=0.05).

Similar trends were noted in small intestinal cancer with concomitant IDA; higher inpatient mortality, 4.5% vs. 3% (p<0.0001), higher hospital costs, $68,699 (± 4874) vs. $65,890 (± 1883) (p<0.0001) and longer length of stay, 9.6 days vs. 8.8 days (p=0.05). IDA also had significant impact on all the three variables in patients with colorectal cancer; inpatient mortality, hospital costs and length of stay were higher 4.5% vs. 2.3% (p< 0.0001), $55,753 (± 367) vs. $49,466 (± 932) (p< 0.0001), and 9.1 days vs. 8.6 days (p=0.05) respectively.

Conclusions: With cancer imminently emerging as the number one cause of death in the United States, cancer-related comorbidities have an unequivocal effect on disease prognosis. IDA is a commonly found and well recognized complication of luminal gastrointestinal cancers. Notwithstanding the limitations of a billing code based retrospective study, we observed that in patients with luminal gastrointestinal cancers associated with iron deficiency anemia, inpatient mortality was significantly higher compared to those without IDA. Hospital costs and length of stay likewise, were higher in patients with a luminal gastrointestinal cancer and IDA. We hypothesize that iron deficiency anemia is an independent prognostic factor that has direct impact on mortality and as an extension, morbidity in patients with luminal gastrointestinal cancers. Open for future exploration with prospective studies are the impacts of iron deficiency anemia on cancer-related overall survival and not just inpatient mortality, and the effect of early identification and treatment of IDA on survival and health care costs.