The main factors thought to contribute to the development of iron deficiency in patients with cancer are1,2:
- reduced intake of dietary iron
- chronic bleeding
- chronic inflammation
- anticancer therapy including chemotherapy
- increased iron requirements during ESA therapy
Figure 3. Why patients with cancer become iron deficient2
Chronic blood loss
Iron lost through bleeding can be clinically significant in oncology patients. The higher prevalence of iron deficiency in pancreatic and colorectal cancers may be a reflection of chronic gastrointestinal bleeding associated with these malignancies1.
Reduced intake of dietary iron
Patients with cancer may not be gaining enough iron from their diet due to disease- or treatment-related anorexia.
Anticancer therapy, including chemotherapy and radiotherapy, is likely to be a factor in the pathogenesis of iron deficiency. The incidence of iron deficiency has been shown to be higher in patients who have recently received treatment (i.e. within 12 weeks) compared with those whose last treatment was more than 12 weeks ago (48 vs 36%; p<0.001)1.
Chronic inflammation is a major cause of iron deficiency in patients with cancer2. Inflammatory cytokines stimulate an increase in the level of hepcidin, an iron homeostasis hormone responsible for controlling the absorption of iron from the intestine, as well as the release of iron from stores within the body3.
Poor absorption of iron may mean that orally administered iron is not as effective as intravenous iron for patients with inflammation (please see ‘Treating iron deficiency in cancer patients’).
Increased levels of hepcidin
Pathological increases in hepcidin impair the release of iron from iron stores, resulting in functional iron deficiency in the short term2. Absorption of iron from the intestine is also blocked by hepcidin, preventing iron stores from being replenished and leading to absolute iron deficiency over the longer term2.
The effect of ESA therapy on iron deficiency in cancer patients
ESA therapy can be used for the treatment of anaemia in cancer patients4–7. However, the sudden demand for iron stimulated by ESA-induced erythropoiesis can cause a rapid depletion of iron stores and result in functional or absolute iron deficiency8.