International and national groups for cancer care professionals have issued guidance on iron deficiency diagnosis including thresholds for iron level markers that should trigger consideration of iron therapy (see table below)1-4. The European Society for Medical Oncology recommends iron levels and inflammation are evaluated by transferrin saturation (TSAT), ferritin and C-reactive protein (CRP) measurement at presentation and then periodically throughout the course of treatment for iron deficiency1.
A patient’s TSAT value indicates the amount of mobilised iron available for erythropoiesis and other functions, while serum ferritin levels are indicative of the level of iron stores in the body and help distinguish between functional and absolute iron deficiency (See the 'Identification and diagnosis of iron deficiency' section of 'Iron Essentials').
Table 1. Definitions of functional and absolute iron deficiency in patients with cancer
The effect of inflammation on serum ferritin measurements
The presence of cancer- or treatment-related inflammation can increase ferritin levels and give an erroneous impression of normal or high iron stores when iron available for use is low. It is therefore recommended that inflammation and liver function be assessed through measurement of CRP and aminotransferases1.
Given the limitation of ferritin as a marker of iron deficiency in cancer, a TSAT level of <20% is considered the threshold at which iron therapy should be considered5. However, the National Comprehensive Cancer Network (NCCN) guidelines on cancer-related anaemia recommend considering iron therapy for ESA-treated patients with a TSAT score <50% and ferritin ≤800 ng/mL2. Additionally, the NCCN serum ferritin level >800 ng/mL indicates that iron therapy is not required regardless of the TSAT score.