Chest X-ray and staging CT in cancer

At a glance

• Chest X-ray is a first test, not an exclusion test. A normal film in a symptomatic smoker doesn't rule out lung cancer.
• CT chest, abdomen and pelvis with IV contrast (portal venous phase) is the standard staging scan for most solid tumours. Brain imaging is added for lung cancer, melanoma and neurological symptoms, with MRI preferred to CT.
• Size criteria are crude. Nodal stage is decided by PET-CT and sampling, not CT alone.
• RECIST 1.1 measures response in trials and in practice; iRECIST adapts it for immunotherapy.

PET, MRI and bone scan are in MRI, PET and nuclear bone scan in cancer. Lung nodule and metastasis patterns are in pulmonary and pleural metastases.

Chest X-ray

What to look for in a patient with known or suspected cancer:

Finding	Think of
Mass or nodule, spiculated	Primary lung cancer
Multiple round nodules ("cannonball")	Metastases: renal, sarcoma, colorectal, testicular, melanoma
Lobar collapse, raised hemidiaphragm	Central obstructing tumour; phrenic nerve invasion
Unilateral effusion, no shift or shift toward it	Malignant effusion with collapse, or mesothelioma
Widened mediastinum, right paratracheal mass	Nodal disease, lymphoma, SVC obstruction
Fine reticular lines, Kerley B lines	Lymphangitis carcinomatosa
Lytic rib lesion, pathological fracture	Bone metastasis, myeloma
Pneumothorax after chemotherapy	Cavitating or sarcoma metastases

• Sensitivity for lung cancer in symptomatic people is about 77 to 80% (Bradley 2019). Tumours hide behind the heart, at the hila, in the apices and below the diaphragm dome.
• The lung cancer optimal care pathway treats unexplained haemoptysis as needing urgent investigation and referral, along with persistent symptoms (over 3 weeks) or a suspicious film. A normal film doesn't end the work-up: with persistent symptoms or haemoptysis, especially in an older smoker, arrange a CT chest.
• Screening uses low-dose CT, not X-ray. The National Lung Cancer Screening Program (from July 2025) offers CT every 2 years to people aged 50 to 70 with at least 30 pack-years who smoke or quit within 10 years.

Staging CT, step by step

Technique: IV iodinated contrast, portal venous phase. Arterial phase is added for hepatocellular carcinoma and neuroendocrine liver metastases; CT colonography or rectal MRI for local rectal staging.

1. Primary: size, invasion of adjacent structures (T stage).
2. Nodes: short axis over 10 mm is "enlarged" in most stations (over 6 mm for retrocrural, over 15 mm for jugulodigastric). CT has sensitivity about 55% and specificity about 81% for mediastinal nodal metastases in NSCLC.
3. Lungs: nodules. Fleischner rules don't apply to patients with cancer.
4. Liver: hypodense metastases; lesions under 1 cm are often "too small to characterise" and need MRI or follow-up.
5. Adrenals: unenhanced 10 HU or less is a lipid-rich adenoma. Otherwise the options are FDG PET-CT, MRI chemical shift, washout CT (absolute washout 60% or more suggests adenoma) or sampling. The ESE/ENSAT 2023 incidentaloma guideline gives washout CT a limited role; in a patient with cancer, FDG PET-CT or sampling is usually more useful. See adrenal incidentaloma.
6. Bones: lytic or sclerotic lesions on bone windows.
7. Serosa: peritoneal nodules, omental cake, ascites, pleural thickening.
8. Incidental findings that need action: pulmonary embolism (treat as symptomatic, see cancer-associated thromboembolism), hydronephrosis, impending cord compression.

Contrast safety (RANZCR): check eGFR. Risk of contrast-associated AKI is low above an eGFR of 30; below 30, weigh the benefit and give IV hydration if appropriate. Metformin needs to be withheld only if eGFR is under 30 or AKI is present. A previous moderate or severe reaction calls for an alternative test or premedication under radiology guidance.

Measuring response: RECIST 1.1

Baseline: pick up to 5 target lesions (2 per organ), each 10 mm or more in longest diameter (nodes 15 mm or more short axis). Record the sum of diameters. Everything else is non-target.

Category	Definition
Complete response	All lesions gone; nodes under 10 mm short axis
Partial response	Sum down 30% or more from baseline
Progressive disease	Sum up 20% or more from the smallest sum (nadir) and at least 5 mm, or unequivocal non-target progression, or any new lesion
Stable disease	Neither

Worked example

Baseline: liver lesion 40 mm, liver lesion 30 mm, lung nodule 20 mm. Sum 90 mm. Week 9: 25, 20 and 12 mm. Sum 57 mm. Week 18: 30, 24 and 15 mm. Sum 69 mm. No new lesions.

• Week 9: 57/90 is a 37% fall, a partial response. The nadir is now 57 mm.
• Week 18: 69 mm is 12 mm (21%) above the nadir, though still below baseline. That meets progressive disease. Progression is measured from the nadir, not baseline.

iRECIST for immunotherapy

• Pseudoprogression (growth or new lesions from immune infiltrate, then response) occurs in under 10% of patients, more in melanoma.
• First progression is iUPD (unconfirmed). If the patient is clinically stable, continue treatment and rescan in 4 to 8 weeks. Further growth confirms iCPD.
• Don't continue through suspected progression if performance status is falling.

When it changes management

• Resectability: a single liver metastasis from colorectal cancer may still be curable; peritoneal disease usually changes the plan.
• Stage migration: contralateral nodes, adrenal metastasis or pleural nodularity convert curative to palliative intent, but sample before denying surgery if the finding is solitary.
• Response: PD on RECIST triggers a change of line; SD on immunotherapy may mean continue.

Pitfalls

• Treating a normal chest X-ray as reassurance in persistent haemoptysis.
• Calling nodes malignant or benign on size alone.
• Measuring progression from baseline instead of the nadir.
• Stopping immunotherapy at the first new lesion in a well patient.
• Missing an incidental PE on a staging scan.