Table 1 Baseline characteristics of the two subgroups

Median age years (range)

72 (4686)

72 (50 − 81)

73 (46 − 86)

0.297^a)

65 years old and over, n (%)

25 (80.6%)

14 (77.8%)

11 (84.6%)

1.000^b)

Male, n (%)

27 (87.1%)

17 (94.4%)

10 (76.9%)

0.284^b)

Smoking history, yes, n (%)

26 (83.9%)

17 (94.4%)

9 (69.2%)

0.134^b)

Comorbidities, n (%)

 Interstitial pneumonia

10 (32.3%)

7 (38.9%)

3 (23.1%)

0.452^b)

 Chronic obstructive pulmonary disease

18 (58,1%)

12 (66.7%)

6 (46.2%)

0.294^b)

 With pre-onset O₂ administration

4 (12.9%)

4 (22.2%)

0 (0%)

0.120^b)

 Diabetes

11 (35.5%)

5 (27.8%)

6 (46.2%)

0.449^b)

 Chronic kidney disease

10 (32.3%)

8 (44.4%)

2 (15.4%)

0.129^b)

 Hypertension

11 (35.5%)

9 (50.0%)

2 (15.4%)

0.070^b)

 Obesity (BMI over 30)

2 (6.5%)

1 (5.6%)

1 (7.7%)

1.000^b)

 History of administration of cytotoxic anticancer drugs within 14 days, n (%)

17 (54.8%)

10 (55.6%)

7 (53.8%)

1.000^b)

History of ICI administration within 90 days, n (%)

 Total

7 (22.6%)

7 (38.9%)

0 (0%)

0.025^b),*

 Atezolizumab

4 (12.9%)

4 (22.2%)

0 (0%)

-

 Pembrolizumab

3 (9.7%)

3 (16.7%)

0 (0%)

-

 small cell carcinoma

3 (9.7%)

1 (5.6%)

2 (15.4%)

0.198^b)

 squamous cell carcinoma

13 (41.9%)

10 (55.6%)

3 (23.1%)

 adenocarcinoma

14 (45.2%)

7 (38.9%)

7 (53.8%)

 mesothelioma

1 (3.2%)

0 (0%)

1 (7.7%)

 1st line

11 (35.5%)

7 (38.9%)

4 (30.8%)

0.981^b)

 2nd line

6 (19.4%)

4 (22.2%)

2 (15.4%)

 3rd line and above

13 (41.9%)

7 (5.6%)

6 (7.7%)

 adjuvant chemotherapy

1 (3.2%)

0 (0%)

1 (7.7%)

Laboratory data Median [min–max]

 White blood cell (× 10³/µL)

5.0 [1.3 − 11.9]

4.3 [1.6 − 6.9]

0.400^a)

 Neutrophil (× 10³/µL)

3.4 [0.4 − 7.9]

2.8 [0.6 − 5.9]

0.489^a)

 Lymphocyte (× 10³/µL)

0.8 [0.2 − 3.1]

0.7 [0.5 − 1.3]

0.357^a)

 Hemoglobin (g/dL)

10.7 [7.9 − 13.6]

11.3 [9.4 − 13.9]

0.575^a)

 Platelets (× 10³/µL)

193.5 [75 − 424]

165 [27 − 280]

0.562^a)

 Albumin (g/dL)

3.2 [2.2 − 4.0]

3.6 [2.8 − 4.4]

0.296^a)

 LDH (U/L)

234.5 [140 − 418]

206 [139 − 426]

0.483^a)

 AST (U/L)

22 [9 − 44]

28 [17 − 45]

0.054^a)

 ALT (U/L)

19 [6 − 50]

20 [8 − 77]

0.561^a)

 Creatinine (mg/dL)

0.9 [0.49 − 1.54]

0.9 [0.53 − 1.5]

0.305^a)

 CRP (mg/dL)

3.79 [0.04 − 12.6]

1.47 [0.2 − 3.1]

0.017^a),*

 D-dimer (µg/mL)

1.3 [0.7 − 10.2]

1.7 [0.7 − 7.9]

0.641^a)

 Ferritin (ng/mL)

419.1 [185.5 − 1251.8]

356.4 [53.2 − 1006.1]

0.481^a)

 KL-6 (U/mL)

543 [176 − 2440]

452 [162 − 1470]

0.474^a)