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Interventional Oncology Viva Questions

Oral-exam style questions and answers on interventional oncology for MD, DNB and super-specialty practical examinations. Each answer links back to the playbook or Library entry it was written from.

What defines an A0 liver-tumor ablation?: A0 means that the entire tumor is covered by the ablation zone with a quantitatively sufficient circumferential tumor-free margin. A1 means complete tumor coverage but an insufficient margin, whereas A2 means that part of the tumor remains unablated.
What margin should be achieved around a liver tumor?: A minimum margin of at least **5 mm** should be achieved in every direction. For colorectal liver metastases, a **10 mm** margin provides optimal local control when it can be obtained safely.
Why is microwave ablation less affected by heat sink than RFA?: MWA produces an electromagnetic field that directly agitates water molecules and can generate higher temperatures over a larger volume more rapidly. Continued tissue heating is therefore less dependent on electrical current conduction and is less vulnerable to cooling by adjacent blood flow.
Does the visible cryoablation ice ball represent the lethal ablation zone?: No. The visible ice-ball edge is approximately the 0°C boundary, while reliable cell death requires substantially colder temperatures lying several millimetres inside it. The ice ball must therefore extend beyond the tumor and intended lethal margin.
Why is a central hilar tumor dangerous to ablate?: The central bile ducts are highly susceptible to thermal injury and may develop necrosis, biloma, cholangitis or delayed stricture. Tumors within approximately 1 cm of a major duct require active protection, an alternative modality or reconsideration of ablation.
Which patients have the highest risk of liver abscess after ablation?: Patients with an incompetent sphincter of Oddi from bilioenteric anastomosis, sphincterotomy, biliary stenting or drainage have colonized bile ducts and the greatest risk. They require protocolized broad-spectrum prophylaxis, commonly extending for 5–10 days.
Why is 5% dextrose preferred for hydrodissection during RFA?: Five-percent dextrose is non-ionic and does not conduct radiofrequency current. Ionic saline can conduct current away from the electrode and unintentionally increase heating of adjacent tissues.
What is the best imaging endpoint immediately after ablation?: Contrast-enhanced CT or MRI should show no residual tumor enhancement and should permit three-dimensional registration of the pre-ablation tumor with the post-ablation zone. Quantitative margin assessment with confirmation software is preferred over visual side-by-side inspection alone.
What is the fundamental difference between TAE and TACE?: TAE produces tumor ischemia using embolic material without chemotherapy. TACE combines embolization with intra-arterial chemotherapy, either as a chemotherapy–iodized-oil emulsion in conventional TACE or chemotherapy loaded into drug-eluting microspheres.
Why can a hepatic artery be embolized without infarcting the entire liver?: HCC and many hypervascular metastases obtain most of their supply from the hepatic artery, whereas normal liver parenchyma receives most of its perfusion from the portal vein. This differential supply permits selective arterial tumor treatment, provided portal perfusion and hepatic reserve are adequate.
How do you prepare a conventional TACE emulsion?: A water-in-oil emulsion is favored by using more iodized oil than aqueous chemotherapy, usually a 2:1 or 3:1 ratio, and repeatedly pumping the components through a compatible stopcock. It is prepared immediately before administration and followed by particulate embolization.
What is the angiographic endpoint of conventional TACE?: The desired endpoint is pruning of small tumor-feeding radicals with a tree-in-winter appearance while preserving flow in the major lobar and segmental hepatic arteries. Complete proximal occlusion is avoided because it injures normal liver and compromises future access.
Are drug-eluting beads superior to conventional TACE?: Drug-eluting beads provide standardized embolization and lower systemic chemotherapy exposure, but randomized evidence has not shown a consistent overall-survival advantage over well-performed conventional TACE. Technique selection therefore depends on patient factors, tumor type, device availability and institutional expertise.
Is portal-vein thrombosis an absolute contraindication to TACE?: Not invariably. Main portal-vein occlusion, hepatofugal flow and poor collateral perfusion create a high risk of liver failure, whereas selected patients with limited branch thrombosis and preserved liver function may undergo highly superselective treatment. The extent of thrombosis, portal flow, liver reserve and alternatives must be reviewed together.
Which patients have the highest risk of hepatic abscess after embolization?: Risk is highest when the biliary tract is colonized after bilioenteric anastomosis, sphincterotomy, biliary stenting or other loss of sphincter-of-Oddi integrity. These patients require individualized broad-spectrum prophylaxis and close delayed follow-up.
How is response assessed after TACE for HCC?: Multiphasic CT or MRI is performed at approximately 4–6 weeks and viable arterially enhancing tumor is assessed using mRECIST. Tumor enlargement alone is unreliable because treated necrotic tissue may remain visible.

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