Table 1.
Cut-off and criteria for variable categorization
| Variable | Cut-off or criterion |
|---|---|
| Age | >65 years |
| Number of metastases | Single versus multiple (>1) |
| Elevated CEA level | >5 ng/dL |
| Specific Growth Rate | >0.0054/day* |
| Elevated C-reactive protein level | >10 mg/L |
| Low albumin level | <35 g/L |
| Active cigarette smoke exposure | Active smoking until six months before metastatic onset |
| Centrally located metastases | Proximity to a segmental or lobar bronchus/vessel |
| Large size | ≥3 cm (longer axis) |
| Disease-free interval from primary tumor resection | <36 months |
| Nodal involvement of primary tumor | N1–3 (vs. N0) |
This value corresponds to a tumor doubling time of 128 days, according to the formula: tumor doubling time = ln(2)/specific growth rate. CEA, carcino-embryonic antigen.