Infections in the Cancer Patient

Cancer patients are more susceptible to infection than the general population because the malignancy itself and its treatment damage multiple layers of host defense simultaneously — neutrophil number and function, mucosal barriers (severe chemotherapy- or radiation-induced mucositis lets colonizing oral and gut flora translocate into the bloodstream), humoral (B-cell/antibody) immunity, and cell-mediated (T-cell) immunity.^[1] Febrile neutropenia is a medical emergency: because these patients cannot mount a normal inflammatory response, fever is frequently the only sign of a serious infection, and the inability to reliably distinguish an infected from a non-infected neutropenic patient at presentation is exactly why empiric broad-spectrum IV antibiotics are started immediately rather than after a source is found.^[1] This chapter covers febrile neutropenia risk stratification and empiric antibacterial therapy, empiric and prophylactic antifungal and antiviral therapy, colony-stimulating factor use, central-line-associated bloodstream infection, and vaccination considerations in immunosuppressed cancer patients — the areas where a pharmacist's dosing, timing, and de-escalation input most directly affects outcomes.

Fever is often the only sign

Neoplasms themselves can occasionally cause fever, but an infectious cause must be sought and presumptively treated in every febrile cancer patient — the diagnosis is never assumed to be "tumor fever" at first presentation.^[1] Fever is defined as a single oral temperature of 38.3°C or higher, or a temperature of 38.0°C or higher sustained for at least 1 hour, in the absence of an obvious environmental cause.^[1] Neutropenia is defined as an absolute neutrophil count (ANC) of 0.5 ×10⁹/L or lower; profound neutropenia — an ANC under 0.1 ×10⁹/L — confers substantially greater infection risk, and risk rises further the longer neutropenia persists, with neutropenia expected to last more than 7 days considered higher risk than neutropenia expected to resolve within 7 days.^[1]

Where infection typically originates

Most infections arise from organisms that already colonize the patient at or near the site of infection — skin, oropharynx, GI tract, lungs, or genitourinary tract — rather than from a new environmental exposure. Bacteria are the most common documented pathogens in febrile neutropenic episodes, though in most episodes no organism is ever identified.^[1] Local antimicrobial resistance patterns matter directly to empiric drug selection — actively consider the possibility of MRSA, vancomycin-resistant enterococci (VRE), extended-spectrum beta-lactamase (ESBL)-producing Enterobacterales, carbapenem-resistant Enterobacterales, and Candida auris colonization or infection when choosing and escalating therapy.^[1]

Site-specific clues to actively seek

Because classic localizing signs (pus, an infiltrate, urinary symptoms) can be blunted or absent in a neutropenic patient, actively examine and ask about: the oral cavity and pharynx (mucositis, thrush), venous catheter exit sites and tunnels, skin and perianal area (visual inspection only — see Common Errors below), sinuses, chest, and any area of localized pain, swelling, or new neurologic change.^[1]

• Depth of neutropenia — profound neutropenia (ANC under 0.1 ×10⁹/L) carries substantially higher infection risk than moderate neutropenia.
• Duration of neutropenia — neutropenia lasting more than 7 days carries substantially higher risk than neutropenia expected to resolve within 7 days.
• Mucosal barrier injury (oral or GI mucositis) from cytotoxic chemotherapy or radiation, allowing colonizing organisms to translocate into the bloodstream.
• Central venous catheters, implanted ports, and other indwelling devices.
• Humoral immune defects (B-cell/antibody dysfunction) — e.g., chronic lymphocytic leukemia, multiple myeloma, hypogammaglobulinemia.
• Cell-mediated immune defects (T-cell dysfunction) — e.g., lymphoma, prolonged corticosteroid therapy, purine-analogue chemotherapy, alemtuzumab, graft-versus-host disease and its immunosuppressive treatment, allogeneic hematopoietic stem-cell transplantation.
• Functional or anatomic asplenia (splenectomy) — markedly increased risk of overwhelming infection with encapsulated organisms.
• Tumor obstruction of a natural body passage (bronchus, bowel, ureter, biliary tree), impairing normal clearance and predisposing to local infection.
• Malnutrition and poor performance status.
• A prior invasive fungal infection, particularly in a patient who will become neutropenic again.
• Known colonization with a multidrug-resistant organism.
• Extended hospitalization and recent broad-spectrum antibiotic exposure.

History

• History of significant infections and drug allergy/sensitivity, including the specific nature of any prior reaction.
• The nature of the malignancy and its associated host-defense defects (e.g., neutropenia, B-cell and/or T-cell dysfunction).
• The impact of cytotoxic, myelosuppressive, or immunosuppressive therapy — note the day of fever onset relative to the first day of the most recent chemotherapy cycle.
• Neutropenia severity and expected duration, since these are the main predisposing factors for infection.
• Prior iatrogenic procedures — splenectomy, venous access device placement, or other surgery.
• Whether the malignancy could be obstructing a natural body passage (bronchus, bowel, ureter, biliary tree).
• CNS dysfunction — changes in cranial nerve function, strength, coordination, stance/gait, sensation, or mental status.
• Occupational and travel history, and animal exposure.

Physical examination

Complete exam with particular attention to venous access sites, wounds, skin, mouth, pharynx, sinuses, chest, and other possible sites of infection; note any localizing signs — shortness of breath, localized pain, facial or extremity swelling, mental status change, seizures, or focal weakness suggesting a CNS infection. Avoid digital rectal examination and rectal thermometers in a neutropenic patient — mucosal trauma can seed bacteremia; visual perianal inspection only.^[1]

Investigations

• CBC with differential to assess the ANC.
• Biochemical profile with attention to renal and hepatic function.
• At least 2 sets of blood cultures — from a peripheral site and from every lumen of any venous access device.
• Culture of any other suspected site of infection (urine, skin, sputum).
• Radiographic studies appropriate to the suspected site — e.g., chest x-ray or CT for pneumonia, abdominal CT for an intra-abdominal focus, CT/MRI of the extremities for suspected soft-tissue infection, or CT/MRI of the head for suspected encephalitis, meningitis, or cerebral abscess.
• Stool testing for Clostridioides difficile and other pathogens (Salmonella, Shigella, Campylobacter, viruses, protozoa) if diarrhea is present — note that immunotherapy-related colitis can also cause diarrhea and should be considered in the differential.
• Serologic or quantitative PCR testing (adenovirus, cytomegalovirus, Cryptococcus, Epstein-Barr virus, hepatitis, human herpesviruses, respiratory viruses including SARS-CoV-2, Toxoplasma) when clinically indicated.
• Biopsy for pathology and culture of skin lesions or other suspected infectious sources (sinuses, nose, lung, GI tract) when appropriate.

Diagnosing central-line-associated bloodstream infection

Whenever catheter infection is suspected, draw paired blood cultures — one set from a peripheral vein and one set from every catheter lumen — before changing antimicrobial therapy. Growth of the same organism from the catheter-drawn sample at least 2 hours before the peripheral sample turns positive (differential time to positivity) supports a catheter source.^[2]

Risk stratification — which patients can be treated as outpatients

The MASCC (Multinational Association for Supportive Care in Cancer) risk index is a validated, published point-sum used to identify febrile neutropenic patients at low risk for serious complications.^[3] Every criterion below is scored independently and the points are summed.

Maximum possible score is 26. A score of 21 points or higher identifies a patient as low risk for serious complications; a score under 21 identifies high risk, favoring inpatient IV therapy.^[3][4]

On a live calculator: the MASCC index is a genuine, fixed, published point-sum, not a continuously-weighted regression model like GRACE, so it is a reasonable future calculator candidate in principle. However, its "burden of illness" item assigns three different point values (5, 3, or 0) to three graded symptom levels rather than a simple present/absent toggle — a design the site's current checkbox-only calculator pattern (built for the TIMI score) cannot represent without adding a new multi-option control type. This chapter therefore ships the teaching table above for manual scoring rather than a live calculator; the underlying MASCC score itself is not disqualified the way GRACE is.

Meeting the MASCC threshold alone is not sufficient to send a patient home — outpatient management also requires the specific clinical and logistic criteria described in Choose Initial Treatment below.^[4]

• Recognize and treat infection immediately in a febrile neutropenic patient, since infected and non-infected neutropenic patients cannot be reliably distinguished at presentation.
• Cover both gram-positive and gram-negative pathogens, with reliable antipseudomonal activity, from the very first dose.
• Achieve time-to-first-antibiotic-dose within 1 hour of a suspected febrile neutropenic episode.
• Identify low-risk patients who can safely step down to oral or outpatient therapy, and high-risk patients who need continued inpatient IV therapy.
• Add antifungal coverage promptly when fever persists despite appropriate broad-spectrum antibacterial therapy.
• Prevent febrile neutropenia in future chemotherapy cycles for patients at meaningfully elevated risk, using colony-stimulating factors and/or antimicrobial prophylaxis.
• Recognize and manage central-line-associated bloodstream infection promptly, including the decision to remove or salvage the catheter.
• Protect immunosuppressed patients from vaccine-preventable disease without exposing them to live-vaccine risk during immunosuppression.

• Standard precautions, especially hand hygiene, for every immunocompromised patient.
• High-efficiency particulate air (HEPA) filtration rooms for profoundly neutropenic patients at high risk for filamentous fungal infection (e.g., allogeneic stem-cell transplant recipients, prolonged neutropenia).
• Contact precautions for patients colonized or infected with a multidrug-resistant organism — MRSA, vancomycin-resistant enterococci, ESBL-producing Enterobacterales, carbapenem-resistant Enterobacterales, Candida auris, or C. difficile.
• Droplet precautions for respiratory viral illness.
• Airborne precautions for varicella-zoster infection and suspected tuberculosis.
• Avoid fresh flowers and plants in the rooms of neutropenic patients.
• Avoid unnecessary rectal manipulation — digital rectal exam, rectal thermometers, enemas, or suppositories — in neutropenic patients, given the mucosal-trauma bacteremia risk.
• Maintain oral hygiene and mucositis care to reduce the mucosal-barrier-injury route of infection.
• Restricting specific food types (raw fruits/vegetables, raw eggs, aged cheese) in a "low-bacterial diet" is common institutional practice, though supporting evidence is mixed — follow local policy.

Pregnancy

Cancer diagnosis and treatment during pregnancy needs multidisciplinary (oncology, maternal-fetal medicine, infectious diseases) management. Beta-lactams (penicillins, cephalosporins, carbapenems) and vancomycin are preferred first-line given their long safety record. Aminoglycosides are used only when no alternative exists, given a theoretical fetal ototoxicity risk, with close monitoring. Voriconazole and posaconazole are generally avoided in pregnancy given teratogenicity in animal studies; a lipid amphotericin B formulation is generally preferred for invasive fungal infection in pregnancy. Fluoroquinolones are avoided when a suitable alternative exists, but used if a serious infection specifically requires one and no alternative is adequate.

Breastfeeding

Most beta-lactams, cephalosporins, carbapenems, and vancomycin are considered compatible with breastfeeding. Aminoglycosides are largely compatible given poor oral bioavailability to the infant. Fluoroquinolones are now considered compatible by many references despite historic caution. Fluconazole is compatible; voriconazole and posaconazole have limited breastfeeding data — discuss with the treating team before use.

Pediatrics

Dosing throughout the Drug Tables below reflects standard mg/kg regimens usable across the pediatric age range unless otherwise noted. The MASCC risk index is validated in adults only — use an institutional or pediatric-specific febrile neutropenia protocol for risk-based triage decisions in children rather than applying the adult MASCC threshold.

Renal impairment

Vancomycin, aminoglycosides, and most beta-lactams are renally cleared and require dose or interval adjustment, guided by levels where applicable. Prefer oral over IV voriconazole when creatinine clearance is under 50 mL/min, given accumulation of the IV solubilizing vehicle in renal impairment; isavuconazole and posaconazole do not share this issue and are reasonable alternatives. Avoid aminoglycosides when a suitable alternative exists, particularly alongside other nephrotoxic drugs (cisplatin, cyclosporine, amphotericin B, vancomycin).

Hepatic impairment

All azole antifungals are hepatically metabolized and need monitoring; caspofungin requires dose reduction in moderate hepatic impairment, and voriconazole requires dose reduction in mild-to-moderate hepatic impairment.

Hematopoietic stem-cell transplant / graft-versus-host disease

Extended and deeper immunosuppression changes prophylaxis choices — posaconazole is preferred antifungal prophylaxis during active graft-versus-host disease treatment, and letermovir prophylaxis is specific to CMV-seropositive allogeneic transplant recipients. A structured revaccination protocol is typically needed 6-12 months post-transplant once immune reconstitution allows it.

Vaccination

Cancer patients are considered immunocompromised and should not receive live vaccines during a period of significant immunosuppression.^[6] Where the treatment schedule allows planning ahead, give any needed live vaccine at least 4 weeks before starting immunosuppressive therapy, and any needed inactivated vaccine at least 2 weeks before starting it.^[6] The magnitude and duration of the immune response to any vaccine may be reduced while a patient is immunosuppressed, so re-checking vaccine status and considering revaccination once immune function recovers is appropriate, particularly after hematopoietic stem-cell transplantation. Where a live-vaccine alternative exists, household and close contacts of an immunosuppressed patient should preferentially receive the inactivated option (e.g., inactivated rather than live attenuated influenza vaccine).^[6]

Asplenia

Splenectomized or functionally asplenic patients face markedly increased risk of overwhelming infection with encapsulated organisms (S. pneumoniae, H. influenzae, N. meningitidis) — confirm pneumococcal, meningococcal, and H. influenzae type b vaccination status is current (using inactivated vaccines on the standard non-live-vaccine timing above), and discuss a standby-antibiotic plan for fever with the treating specialist.

Reassess clinically and repeat vital signs per institutional protocol until afebrile and stable. Trend the ANC daily with a CBC and differential. Monitor renal function at baseline and regularly during aminoglycoside or vancomycin therapy, with trough or AUC-guided vancomycin levels per institutional protocol. Repeat blood cultures to confirm clearance of documented bacteremia, particularly for S. aureus or Candida. Reassess at 4-7 days if fever persists — add antifungal coverage and consider chest/sinus imaging if not already done. Discontinue G-CSF once the ANC recovers to 0.5 ×10⁹/L or higher when it was used to treat an established neutropenic episode; continue per-cycle prophylactic dosing when used for primary or secondary prevention. De-escalate and narrow antibiotics once culture and susceptibility results return; discontinue vancomycin if no vancomycin-susceptible organism is identified and its original indication has resolved. For a confirmed central-line-associated bloodstream infection, follow blood cultures to clearance, and arrange echocardiography for S. aureus bacteremia (to exclude endocarditis) or an ophthalmologic exam for candidemia (to exclude endophthalmitis). Reassess antimicrobial and antifungal prophylaxis needs at the start of every subsequent chemotherapy cycle, not only the first.

1. Fever persisting 2-4 days on appropriate empiric antibacterial therapy without clinical deterioration: reassess history/exam, repeat cultures, and consider imaging for an occult source; no regimen change is required if the patient remains clinically stable and no new information changes management.
2. Fever persisting 4-7 days despite appropriate broad-spectrum antibacterial therapy, especially with anticipated prolonged neutropenia: add empiric antifungal therapy (caspofungin, liposomal amphotericin B, or voriconazole if invasive aspergillosis is a specific concern) and pursue further imaging.
3. Clinical deterioration or hemodynamic instability at any point: escalate coverage immediately (broaden gram-negative and gram-positive coverage, consider double antipseudomonal coverage pending susceptibilities), involve infectious diseases and critical care, and reculture/reimage.
4. A specific organism is identified: narrow (de-escalate) therapy to the most specific effective agent based on susceptibilities rather than continuing broad empiric coverage indefinitely.
5. Suspected or confirmed central-line-associated bloodstream infection: obtain paired blood cultures (every catheter lumen plus a peripheral vein); start empiric therapy covering coagulase-negative staphylococci, S. aureus, gram-negatives, and Candida in a patient with relevant risk factors; remove the catheter for severe sepsis, tunnel/port-site infection, bacteremia persisting beyond 72 hours of appropriate therapy, or infection due to S. aureus, P. aeruginosa, fungi, or mycobacteria — catheter salvage with systemic therapy plus antibiotic lock therapy may be reasonable for uncomplicated coagulase-negative staphylococcal infection when line access is difficult to replace.
6. Neutropenia fails to resolve on schedule with infection still present: consider adding a colony-stimulating factor, particularly with pneumonia, severe cellulitis, or sinusitis, and involve hematology/oncology regarding marrow recovery.

• Delaying the first dose of empiric antibiotics to wait for a completed workup, imaging, or culture results — time-to-antibiotics within 1 hour is the priority.
• Withholding empiric antibiotics because no source is obvious — most febrile neutropenic episodes never have an identified source, and the fever itself is the indication to treat.
• Adding an aminoglycoside to a beta-lactam as routine "double coverage" — this increases toxicity without an outcome benefit over monotherapy for most patients.
• Continuing vancomycin indefinitely "just in case" once started — discontinue it if no vancomycin-susceptible organism is identified and the indication that prompted it has resolved.
• Performing a digital rectal exam, giving rectal medications, or taking a rectal temperature in a neutropenic patient — mucosal trauma can seed bacteremia.
• Reusing fluconazole empirically for persistent fever in a patient already on fluconazole prophylaxis — breakthrough fever on fluconazole suggests a resistant or mould infection and needs a different antifungal class.
• Avoiding cefepime monotherapy out of an outdated mortality concern — more recent, larger analyses have not confirmed the signal seen in some earlier data.
• Applying the MASCC score to a pediatric patient, or using the score alone to decide outpatient management without confirming the clinical/logistic criteria (reliable follow-up access, no significant comorbidity).
• Missing a central-line-associated bloodstream infection because blood cultures were drawn only peripherally, without a paired sample from every catheter lumen.
• Giving a live vaccine during a period of significant immunosuppression, or missing the window to complete a needed vaccine series before planned immunosuppressive therapy when the schedule allows it.
• Forgetting to reassess antimicrobial and antifungal prophylaxis needs at the start of every new chemotherapy cycle, not only the first.
• Combining an aminoglycoside with another nephrotoxic drug (vancomycin, amphotericin B, cisplatin, cyclosporine) without adjusting monitoring intensity.

How to use this table: Doses are adult doses and require patient-specific confirmation (renal/hepatic function, weight, allergy history). Pediatric dosing is weight-based per the current product monograph unless stated. Drug pricing is intentionally omitted. Select any drug name to open its complete Pharmasist Drug Database page.

Antipseudomonal Beta-Lactams - Empiric Monotherapy Backbone

Any one of these four agents alone provides adequate 1st-line empiric coverage for febrile neutropenia; combining two of them does not add benefit.

Aminoglycosides - Adjunct Only, Never Routine Monotherapy

Reserve for a specific concern about resistant gram-negative coverage or septic shock pending susceptibilities; adding an aminoglycoside to a beta-lactam as routine double coverage increases toxicity without improving outcomes.

Glycopeptides and Gram-Positive Reserve Agents

Add only for a specific gram-positive indication; discontinue if no vancomycin-susceptible organism is identified.

Fluoroquinolones

Anaerobic and Adjunct Antibacterials

Antifungal Triazoles

Echinocandins

Polyenes

Antiviral Nucleoside Analogues - HSV/VZV

Cytomegalovirus-Directed Antivirals

Neuraminidase Inhibitor and COVID-19 Antivirals

There is no role for empiric antiviral use without evidence of specific viral disease.

Antimicrobial Prophylaxis - Pneumocystis jirovecii and Special Populations

Colony-Stimulating Factors