Infections in Patients with Cancer¶
Chapter 79 | Part 4: Oncology and Hematology
KEY CLINICAL POINTS¶
- Chemotherapy-induced neutropenia is the most significant risk factor for infections in cancer patients, increasing susceptibility to bacterial, fungal, and viral pathogens.
- Infections in neutropenic patients require prompt empirical antibiotic therapy, with broad-spectrum coverage for gram-positive and gram-negative organisms.
- Prophylactic antifungal agents like posaconazole or echinocandins are recommended for patients with prolonged neutropenia (ANC <500/µL) and high-risk factors.
- Neutropenic fever (NF) is defined as a temperature ≥ 38.3°C with ANC <500/µL or expected to drop below this threshold within 48 hours.
- Invasive fungal infections (IFD) such as aspergillosis and Pneumocystis jirovecii pneumonia (PJP) are critical to diagnose early in immunocompromised patients.
1. DEFINITION & OVERVIEW¶
Infections in cancer patients are a major complication of malignancy and its treatment, contributing to increased hospitalization and mortality. Prevention, diagnosis, and treatment of infections are critical to improving survival and quality of life. The infectious diseases consultant collaborates with multidisciplinary teams to manage these risks.
Table 79-1: Immune Defects and Associated Infections in Cancer Patients¶
| HOST DEFENSE DEFECT | PREDOMINANT PATHOGENS | PATIENTS WITH CANCER AT GREATEST RISK |
|---|---|---|
| Neutropenia (ANC <500/µL) | Gram-negative and gram-positive bacteria | Cytotoxic chemotherapy, underlying hematologic malignancy (e.g., myelodysplasia, acute leukemia) |
| Prolonged (‡10 days), profound neutropenia (ANC <100/µL) | Candidemia, invasive aspergillosis, HSV reactivation, respiratory viral infections | Induction/reinduction therapy for acute leukemia; pancytopenia |
| T cell immunodeficiency | Common bacterial infections, intracellular bacteria (e.g., Listeria monocytogenes), Nocardia species, tuberculosis, NTM | Underlying hematologic malignancy including primary T cell malignancies |
| B cell immunodeficiency | Encapsulated bacteria (Streptococcus pneumoniae, Haemophilus influenzae), respiratory viral infections | Lymphoid malignancies (e.g., chronic lymphocytic leukemia, multiple myeloma) |
| Splenectomy and functional asplenia | Encapsulated bacteria (can result in life-threatening sepsis), malaria, babesiosis | Functional asplenia in chronic GVHD |
| HOST DEFENSE DEFECT | PREDOMINANT PATHOGENS | PATIENTS WITH CANCER AT GREATEST RISK |
|---|---|---|
| Systemic corticosteroids | Broad suppressive effect on innate and adaptive immunity | Corticosteroids are common components of antineoplastic regimens for hematologic cancers |
1.1 Neutropenic Fever¶
Neutropenic fever (NF) is defined as a single oral temperature ≥ 38.3°C or a temperature ≥ 38.0°C sustained for ≥ 1 hour, with ANC <500/µL or expected to decrease to <500/µL within 48 hours. NF is a clinical emergency requiring immediate antimicrobial therapy.
1.2 Invasive Fungal Infections¶
Invasive fungal infections (IFD) are a leading cause of mortality in neutropenic patients. Common pathogens include Aspergillus species, Candida, Pneumocystis jirovecii, and mucormycosis. Early diagnosis and antifungal prophylaxis are critical.
2. EPIDEMIOLOGY¶
Infections are a leading cause of morbidity and mortality in cancer patients. Risk factors include neutropenia, immunosuppressive therapies, mucosal injury, and central venous catheters. Patients with hematologic malignancies, solid tumors, and those undergoing stem cell transplantation are at highest risk.
2.1 Incidence and Prevalence¶
Infections are common in patients with neutropenia, with bacterial infections accounting for the majority of cases. Fungal infections are more prevalent in patients with prolonged neutropenia or immunosuppression.
2.2 Risk Factors¶
Key risk factors include chemotherapy-induced neutropenia, corticosteroid use, immunosuppressive therapies, mucosal injury, and central venous catheters. Patients with hematologic malignancies and those undergoing stem cell transplantation are at highest risk.
3. ETIOLOGY & PATHOPHYSIOLOGY¶
Infections in cancer patients arise from multiple mechanisms, including neutropenia, immunosuppression, mucosal injury, and disruption of physical barriers. Chemotherapy, radiation, and immunosuppressive therapies compromise host defenses, increasing susceptibility to infections.
3.1 Neutropenia¶
Chemotherapy-induced neutropenia is the most significant risk factor for infections. Prolonged neutropenia (ANC <500/µL) increases the risk of bacterial, fungal, and viral infections.
3.2 Immunosuppression¶
Immunosuppressive therapies, including corticosteroids, B cell-depleting agents, and T cell-targeted therapies, impair both innate and adaptive immunity, increasing susceptibility to opportunistic infections.
4. CLINICAL FEATURES¶
Clinical manifestations of infections in cancer patients vary by pathogen and immune status. Common symptoms include fever, chills, and localized signs of infection. Systemic infections may present with sepsis, organ dysfunction, or disseminated disease.
4.1 Neutropenic Fever¶
Neutropenic fever is characterized by fever in the absence of localizing signs. It is a clinical emergency requiring immediate antimicrobial therapy.
4.2 Invasive Fungal Infections¶
Invasive fungal infections (IFD) present with fever, respiratory symptoms, and systemic signs of sepsis. Common pathogens include Aspergillus, Candida, and Pneumocystis jirovecii.
5. DIFFERENTIAL DIAGNOSIS¶
Differential diagnosis of fever in neutropenic patients includes non-infectious causes such as tumor lysis syndrome, drug reactions, and immune reconstitution inflammatory syndrome (IRIS). Non-infectious causes must be considered in the absence of localizing signs.
5.1 Non-Infectious Causes¶
Non-infectious causes of fever include tumor lysis syndrome, drug reactions, and immune reconstitution inflammatory syndrome (IRIS). These must be considered in the absence of localizing signs of infection.
6. INVESTIGATIONS & DIAGNOSIS¶
Diagnostic evaluation of infections in neutropenic patients includes blood cultures, imaging, and molecular diagnostics. Empirical antimicrobial therapy is initiated based on clinical suspicion and risk factors.
6.1 Laboratory Tests¶
Blood cultures, CBC with differential, and inflammatory markers (CRP, lactate) are essential. PCR for respiratory viruses and fungal antigens (e.g., galactomannan, β -d-glucan) are useful for diagnosing IFD.
6.2 Imaging¶
Chest X-ray, CT, and ultrasound are used to evaluate for pneumonia, abscesses, and other infections. CT-PET may be used to assess for fungal infections.
7. MANAGEMENT & TREATMENT¶
Management of infections in neutropenic patients includes empirical antimicrobial therapy, antifungal prophylaxis, and supportive care. Treatment is tailored to the suspected pathogen and immune status.
7.1 Antimicrobial Therapy¶
Empirical therapy for neutropenic fever includes broad-spectrum antibiotics (e.g., meropenem, vancomycin, azithromycin). Coverage for gram-positive and gram-negative organisms is essential.
7.2 Antifungal Prophylaxis¶
Antifungal prophylaxis (e.g., posaconazole, echinocandins) is recommended for patients with prolonged neutropenia (ANC <500/µL) and high-risk factors.
8. PROGNOSIS & COMPLICATIONS¶
Infections in neutropenic patients are associated with high mortality, particularly for invasive fungal infections. Complications include sepsis, organ failure, and mortality from septic shock.
8.1 Mortality¶
Invasive fungal infections (IFD) have a mortality rate of 30–50% in neutropenic patients. Bacterial infections have lower mortality but can be life-threatening in immunocompromised hosts.
9. SPECIAL CONSIDERATIONS¶
Special considerations include managing infections in pregnancy, pediatrics, and the elderly. Prophylaxis and treatment strategies must be adjusted for these populations.
9.1 Pregnancy¶
Antimicrobial and antifungal agents must be selected with caution during pregnancy. Prophylaxis for PJP and IFD is recommended for pregnant patients with hematologic malignancies.
9.2 Pediatrics¶
Pediatric patients with cancer require careful monitoring for infections due to their immature immune systems. Prophylactic antifungals and antibiotics are often used.
10. KEY POINTS & CLINICAL PEARLS¶
Key points include the importance of early antimicrobial therapy for neutropenic fever, the role of antifungal prophylaxis in high-risk patients, and the need for multidisciplinary management of infections in cancer patients. Clinical pearls emphasize the importance of early diagnosis, de-escalation of antibiotics, and monitoring for complications.