The purpose of this study is to evaluate the usefulness of procalcitonin test for differentiation of the cause of pneumonia in patients with cancer.

Serum procalcitonin test is currently used as the biomarker for bacterial infection. Especially, procalcitonin test has been reported to be helpful in differentiating bacterial pneumonia from viral pneumonia, acute exacerbations of interstitial pneumonitis or chronic obstructive lung disease. However, it is not known whether procalcitonin test can help distinguish bacterial pneumonia from non-bacterial pneumonia such as radiation pneumonitis or chemotherapy-induced pneumonitis in patients with cancer.

The aim of this prospective cohort study is to observe the clinical benefits of procalcitonin test for differentiation of the cause of pneumonia in patients with cancer.

Inclusion Criteria:

• Age greater than 18 years
• Patients who have symptoms and suspected imaging findings compatible with pneumonia

Exclusion Criteria:

• Patients who have been treated with antibiotics or steroid therapy.

1. Patients who are suspected of acute pneumonia due to symptoms and imaging findings compatible with pneumonia can be enrolled in this cohort.

   • suspected symptom: cough, sputum, dyspnea or fever/chill
   • suspected image findings: consolidation or ground-glass opacity on chest radiograph or CT

2. All patients enrolled in this cohort undergo procalcitonin test in addition to basic microbiological test.

   • basic microbiological test: blood culture, sputum gram stain/culture, pneumococcal urinary antigen, legionella urinary antigen, mycoplasma antibody etc.