Anemia Associated with Cancer

Article written and reviewed by Dr Luca Moretti

Anemia associated with cancer is one of the most frequent and clinically significant complications of solid tumors and hematologic malignancies (see general definition). It is a multifactorial condition characterized by complex pathophysiology and important prognostic implications: it is associated with lower treatment tolerance, worse quality of life and an unfavorable prognosis; the relationship with survival does not necessarily demonstrate direct causality. Correct identification of the etiology and mechanisms involved is essential for effective management and prevention of the most serious complications.

Epidemiology and clinical relevance

The prevalence of anemia in patients with cancer varies widely according to tumor type, stage, ongoing therapies and the patient's general condition. It is more frequent in advanced carcinomas, including gastrointestinal, pulmonary and gynecologic cancers, in lymphomas and multiple myeloma, and in tumors treated with intensive chemotherapy or radiotherapy. In patients with metastatic disease, anemia tends to be more severe and refractory.
Cancer related anemia is associated with more advanced disease, poorer quality of life and worse prognosis and may limit delivery of treatment; these associations do not demonstrate that anemia alone causes infections, reduces antitumor efficacy or determines survival.

Etiology and specific pathogenetic mechanisms

Anemia in cancer is usually the result of interacting and overlapping mechanisms that may vary over time and among different patient subgroups:

• Chronic tumor related inflammation: many malignancies induce a systemic inflammatory response with cytokine production. IL-6 is one of the main cytokine stimuli for hepatic synthesis of hepcidin; TNF-α and IFN-γ contribute mainly to other mechanisms of iron restriction and suppression of erythropoiesis. Increased hepcidin reduces iron release from storage sites, producing functional iron deficiency, and reduces intestinal absorption. The bone marrow shows a hypoproliferative response.
• Bone marrow infiltration: hematologic malignancies such as leukemias, lymphomas and myelomas, and some bone metastases, may replace or compress normal hematopoiesis, resulting in pancytopenia or severe anemia.
• Acute or chronic bleeding: gastrointestinal, gynecologic, urothelial and pulmonary tumors are often associated with occult or overt bleeding, with iron loss and development of associated iron deficiency anemia.
• Chemotherapy, radiotherapy and drugs: many anticancer regimens cause myelosuppression through direct inhibition of erythroid proliferation, increased red blood cell turnover, hemolysis or toxic effects on hematopoietic stem cells. Some biologic agents, for example anti-CD20 antibodies and tyrosine kinase inhibitors, may induce immune anemia or alter iron metabolism.
• Nutritional deficiencies: anorexia, malnutrition, malabsorption and cancer cachexia aggravate deficiencies of iron, folate, vitamin B12 and other micronutrients essential for erythropoiesis.
• Secondary renal or hepatic insufficiency: in advanced tumors, organ involvement may reduce erythropoietin (EPO) synthesis, alter vitamin B12 and folate metabolism or promote a systemic inflammatory state.

Several factors often coexist, making individualized analysis of the predominant mechanisms necessary in each patient.

Clinical picture and systemic impact

Clinical presentation is extremely variable and depends on the speed of onset, the degree of anemia and the general condition of the patient with cancer. The main symptoms include:

• Marked asthenia and reduced exercise tolerance
• Pallor of the skin and mucous membranes, dyspnea, tachycardia, palpitations
• Cognitive changes, reduced ability to concentrate, insomnia
• Delayed recovery after treatment and worsening quality of life

Anemia may limit the ability to continue cancer treatments at the optimal dose and schedule and increase transfusion requirements, with the corresponding potential complications.
In hematologic malignancies, anemia is often associated with other cytopenias, including neutropenia and thrombocytopenia, increasing the risk of bleeding and infection.

Differential diagnosis and targeted investigations

Diagnosis of anemia in patients with cancer requires systematic assessment of possible causes, which often coexist:

• Medical history: assessment of cancer history, current or previous treatments, bleeding episodes, signs of malnutrition and systemic symptoms.
• Physical examination: evaluation for pallor, hepatosplenomegaly, lymphadenopathy, palpable masses, signs of bleeding and infections.
• Complete blood count and peripheral smear: definition of red blood cell morphology, presence of other cytopenias, schistocytes when microangiopathy is suspected, and circulating blasts.
• Iron indices: ferritin, serum iron, transferrin saturation; attention to possible alteration of values in the presence of inflammation.
• Vitamin B12 and folate measurement: assessment for nutritional deficiencies, especially in patients with impaired absorption or anorexia.
• Hemolysis profile: LDH, indirect bilirubin, haptoglobin, elevated reticulocytes in acute hemolysis.
• Evaluation for occult bleeding: fecal occult blood testing, endoscopy and imaging when indicated.
• Bone marrow examinations: reserved for cases with suspected bone marrow infiltration, including bone marrow biopsy and aspiration.
• Renal and hepatic function and inflammatory markers: to identify possible secondary contributions.

It is essential to distinguish pure anemia of chronic disease from overlapping forms such as iron deficiency, megaloblastic, hemolytic and myelophthisic anemia in order to establish appropriate treatment.

Therapeutic management and integrated strategies

Management of anemia associated with cancer is complex and must be individualized:

• Treatment of the primary cause: control of the malignancy may lead to resolution of anemia, for example following response to chemotherapy in lymphomas, myelomas and leukemias.
• Transfusion support: indicated in severe symptomatic anemia, acute bleeding, inability to use other strategies or in patients receiving advanced palliative treatment. The risk of iron overload and transfusion reactions must be carefully assessed.
• Iron therapy: useful in forms with documented iron deficiency; the intravenous route is preferable in patients with inflammation, malabsorption or myelotoxic treatments.
• Erythropoiesis-stimulating agents (ESAs): may be offered for chemotherapy associated anemia when cancer treatment is not intended to be curative and Hb is <10 g/dL, after correction of reversible causes and discussion of benefits, thromboembolic risk and possible oncologic effects. Transfusion remains an alternative. During ESA therapy, hemoglobin should be maintained at the lowest concentration sufficient to avoid or reduce transfusions. In the absence of a response within 6–8 weeks, the ESA should be discontinued and cancer progression, iron deficiency and other correctable causes of anemia must be reassessed.
• Vitamin supplementation: vitamin B12 and folate supplementation in cases of confirmed deficiency.
• Management of complications: targeted treatment of infections, bleeding and related symptoms; multidisciplinary nutritional support.
• Experimental therapies: modulators of hepcidin and iron metabolism are under investigation but are not standard treatment for cancer related anemia; complement inhibitors have specific indications and are not a general treatment for anemia associated with cancer.

Monitoring must be regular, with reassessment of the strategy according to clinical response, evolution of the malignancy and the emergence of complications.

Complications and future perspectives

The main complications of anemia in patients with cancer include:

• Association with unfavorable prognosis and reduced overall survival
• Repeated-transfusion syndrome (iron overload, immunologic sensitization)
• Delays in treatment protocols and worsening tolerance of treatment
• Negative impact on quality of life, physical performance and functional status
• Thromboembolic complications associated with ESAs and with the malignancy itself

Future perspectives include identification of new predictive biomarkers, development of therapies targeting regulation of iron metabolism, use of selective anti-inflammatory drugs and strategies to personalize supportive treatments.

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