Role of commonly used imaging modalities in the diagnosis and staging of patients suitable for radical treatment
| Imaging modality | Diagnosis | T stage | N stage | M stage | Comment |
| Chest x-ray | Often included as part of initial investigation in primary care and useful to differentiate benign from malignant disease | Limited information compared with MDCT | Provides little information | Obvious metastases may be visible (eg, lung or rib) | Now sometimes omitted from investigation pathway if other presenting factors suggest cancer* |
| MDCT | Often helpful to differentiate benign from malignant disease | Able to measure tumour size accurately. Less reliable for distinguishing T3 from T4; 55% sensitivity, 89% specificity (axial CT) |
| May show clear evidence of mediastinal invasion or metastatic disease but histological confirmation or further staging required if any doubt | Provides excellent triage of patients by identifying clear evidence of cancer, no evidence of cancer ± other diagnoses or uncertainty. Guides the next test. May detect other significant coexistent disease |
| PET-CT | Not currently performed for initial diagnostic purposes | Complements MDCT and can help estimate tumour extent where tumour abuts abnormal tissue (eg, lobar collapse) | More accurate than CT. Sensitivity 84%, specificity 89%. Further mediastinal sampling deemed unnecessary if PET negative and nodes <1 cm.† 10% will have occult disease12 | Sensitivity and specificity to detect distant metastases 93% and 96%, respectively. May detect metastases in up to 15%. Sensitivity for brain metastases only 60%17–21 | Also useful in radiotherapy planning and may have a role in predicting outcome14–16 |