Procedure Guides
Oncology

Tumor Ablation

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Procedure Guide

Non-thermal

  • Histotripsy: focused ultrasound pulses to cause cavitation and non-thermal tissue destruction. Now FDA approved HistoSonics system. Very precise and evidence of at least some abscopal effect.

  • Chemical, e.g., ethanol: better for lesions with capsule like HCC, long track record, no heat sink BUT nonuniform distribution, worse results particularly with larger lesions than thermal ablation in multiple studies, ethanol toxicity

  • Irreversible electroporation (IPE): no heat sink, fast and uniform ablation BUT less data, limited availability, requires GA, increased bleeding risk (no cautery), issues w/ arrhythmias

  • Pulsed electric field (PEF) or “galvanized ablation”: similar to IPE, promising synergistic effect with immunotherapy and abscopal effect but can only treat 1 cm sphere per minute via 19G needle with filament inside.

Hyperthermic

  • RFA: long track record, numerous devices BUT requires grounding pads, can’t have pacemaker or ICD, heat sink issues, longer ablation times (can’t activate multiple probes at once)

  • Microwave: less heat sink, faster and hotter ablation, not restricted by high impedance structure (e.g. lung, bone, char) unlike RF BUT shorter track record, some devices have oblong ablation zones and shaft heating

Hypothermic

  • Cryoablation: less painful, more immunomodulation, better ablation zone visualization BUT cold sink issues, longer ablation times, higher bleeding risk (more have no cautery, more bleeding in the lungs, some evidence though that tract ablate doesn’t reduce bleeding risk), cryoshock (tends to occur in liver with large ablation zones, e.g, >35% liver volume)

Generally smaller isolated mass or few masses. More often recommended for poor surgical candidates or those with need to reserve organ tissue (i.e. poor reserve otherwise).

  • Lung: Stage IA who are poor surgical candidates, lung primary or metastases <3 cm, salvage therapy after chemoradiotherapy

  • Bone: Osteoid osteomas and painful bone metastases

  • Breast: Benign fibroadenomas up to 4.5 cm and breast cancer up to 1.5 cm in poor surgical candidates.

  • Other: painful soft tissue lesions for palliation or potential abscopal effect with galvanized ablation (ongoing research)

For primary treatment (e.g. HCC, RCC)

  • Life expectancy <1 year

  • Distant metastases

  • Larger tumors, some say >5 cm

Adjacent vital structure

  • Subdiaphragmatic or adjacent the hilum for the liver

  • Spine metastasis with extension through the posterior cortex AND neural deficits. Evidence suggests extension into the epidural space without neural involvement can be safely treated.

Adjacent large blood vessel for thermal ablation due to heat sink - 3-4 mm vessel for RFA, less important for microwave

Uncorrected coagulopathy (INR >1.7, Plts <50K)

Active infection (ablated tissue can serve as nidus for infection)

Pacemaker or ICD for RFA

Ablation generally +90% efficacy and similar to resection and SBRT for local control of small lesions <3 cm

Kidney

  • Active survaillence: favored if elderly, life expectancy <5yrs, <3cm, predominantly cystic

  • Partial nephrectomy usually better if >4 cm but lower complications and smaller GFR decrease with ablation

  • Cryoablation is most common but some are using microwave

  • Survival for ablation of T1a RCC: 97% (1yr), 91% (3yrs), 91% (5yrs)

  • Risk of recurrence: RFA 5.2% (0-12.2%), MWA 3.1% (0-17.1%), Cryo 6.7% (2.1-16.4%), Partial nephrectomy 1.6% (0-8.1%)

  • Embolization + ablation > ablation alone if >5 cm

Liver

Lung

  • Surgical resection is generally preferred if a candidate

  • Radiotherapy superior to ablation for larger primary tumors (>3 cm), but equivocal survival for smaller lesions and complications. ~60% of lesions after radiotherapy have viable tumor cells.

  • Stage 1A lung cancer ablation survival: 78% (1yr), 36% (3yrs), 27% (5yrs)

  • ~80-90% local control for cryoablation and RFA, 90+% for microwave

  • Pulmonary mets 1 +/- 1.2 measuring 1.0 +/- 0.6 cm: 98% 1-yr OS, 5.3% complications (SOLSTICE trial)

  • Can be performed with co-existing ILD though acute exacerbations may occur in 8% with 60% mortality among those patients. Predictive factors for exacerbation include post-procedure fever or effusion.

Bone

  • Osteoid osteoma: 92% primary success, 99.6% secondary success

  • Bone mets: ~50% subjective pain decrease, pain score reduction of 4.10-5.25, 90% local tumor control

    • Ablation vs radiation: ablation is ideal for shorter life expectancy (works faster than radiation, ~1 wk vs 4-6 mo), in combination with radiotherapy (allows patient to tolerate lying on the table still better for radiotherapy), or radioresistant lesions (sarcoma, RCC, NSCLC, melanoma)

    • Ablation vs embolization: embolization is better if hypervascular, >5cm, or adjacent structures preventing safe ablation (nerves, hollow organs).

    • Ablation + cementoplasty is superior to ablation or cementoplasty alone in terms of pain relief and less cement leakage and adjacent fractures during follow up.

    • Average palliative bone met ablation outcomes: ~50% subjective pain decrease (more recent studies reporting >80-90%), pain score reduction of 4.10-5.25, 90% local tumor control. OPus One Trial - ablation for lytic bone mets was durable (sustained results at 12 mo) and effective (pain, disability, QoL)

    • Efficacy and complication rates vary and data is heterogeneous but RF and cryoablation may be safer than microwave ablation.

Breast

  • Highly successful (92-100%) in reported small studies in terms of local control. Complications are rare, usually just localized swelling, local pain, erythema.

  • Complete regression at 3 months superior with cryoablation compared to microwave ablation (96 vs 75%)

High-intensity focused ultrasound ablation: generally safe but no comparative trials

Laser ablation: limited data

Labs for bleeding risk and organ function, e.g., Cr for kidney

Consider spirometry for lung ablation if history of diffuse lung disease or surgery, ideally FEV1 should be >1L

Ensure proper staging often in collaboration with tumor board or oncologist

Review pre-procedure cross sectional imaging for planning/safe approach

  • RENAL Nephrometry score: Used for stratifying partial nephrectomy risk. Some suggest this can be used to estimate ablation risk. Others note that some metrics don’t apply and really only size, older age, more probes, and central tumor location matter in terms of complication risk

Pre-ablation biopsy recommended for renal lesions per 2020 SIR Position Statement and 2021 AUA guidelines as 40% masses <1 cm and 25% <3 cm end up being benign, help guide future management with genetic testing and targeted therapy

Some stop Avastin 2-4 weeks prior

Some give IV hydration if GFR 30-60 for renal ablation

Shave and place grounding pads and protective pads for areas with neurovascular bundles if using RFA

General anesthesia is generally preferred. Some use moderate sedation for cryoablation.

  • Pre-scan (CT, US, MRI), mark skin, local anesthesia

  • (Optional) Place needle or catheter is hydrodissection or pneumodissection is being used

  • (Optional) Placement of retrograde ureteral catheter for saline infusion with assistance of urology if using for collecting system protection

  • Select and place ablation probe(s)

    • Some suggest 2 probes of 1.5 cm diameter bracketing lesion up to 2 cm. Should target ablation zone 1 cm larger than lesion in all directions. CT may overestimate for lung, so targeting 1.2 cm may be better.

    • Tricks for lung lesions: (central) approach parallel to bronchovascular tree; (peripheral) tangential approach so ablation zone stays within visceral pleura

      • If lesion adjacent critical structure, can create PTX or use stick mode and move lesion away

      • If lesion adjacent vessel, approach parallel to vessel and heat safe side longer (e.g. 5 min) and vessel side shorter (e.g. 2 min) to finish off area adjacent the vessel

      • Wait 5 min to judge GGO ablation zone (CT over estimates slightly)

      • Use cryoablation for lesions near pleura (<3 cm)

    • Tricks for abdominal lesions: Hydrodissection w/ 1:30-50 dilute contrast in D5W. Don’t be stingy. Some have infusion running throughout the procedure. Can use pneumodissection, catheters, balloons. Target base of exophytic lesion tangential to kidney.

  • Ablate the lesion(s) with CT and/or US monitoring

    • Cryoablation: typically two 10-min cycles of argon freeze with passive thaw in between

    • RFA/Microwave: cell death within few minutes >50*C or few seconds >60*C, increase power to overcome heat sink with adjacent major vessel with MWA

    • Ethanol: volume required = 4/3 * 3.14 * (r + 0.5)^3; often 15 mL for 2 cm, 35 mL for 3 cm, and 65 mL for 4 cm; some people just default to 30 mL 

  • Confirm target ablative margin via CE-CT and/or 3D modeling software if available/necessary

    • Margin of at least 5 mm, better if 10 mm. Nearly no local recurrence if 3D tracking software is used to confirm 3D 10 mm margins

    • NOTE for lung, ablative zone is dense core + lucent ring, NOT surrounding rim of hemorrhage

    • For palliative metastasis ablation, treatment of the entire lesion is not possible. For bone metastases, patients tend to get superior pain relief with treatment of the bone-tumor interface.

  • (Optional - bone mets) Some perform vertebral augmentation, cementoplaty, and percutaneous screw fixation after ablation to provide support and prevent pathologic fractures

    • RF ablation + augmentation is superior to ablation or augmentation alone for spine mets in few small studies in terms of pain relief and less cement leakage and adjacent fractures during follow up

  • Pull out probe gently, rotating to avoid shearing blood vessels. Can ablate track to reduce bleeding risk if using hyperthermic ablation.

  • If PTX, can aspirate and wait 10-15 min to see if it re-expands before placing chest tube

Death (0.1-0.5%): often secondary to complications such as sepsis, hepatic failure, colon perforation, PV thrombosis

Major adverse event (2-3%): internal bleeding, large pneumo/hemothorax, abscess, vital structure damage (e.g. bowel perforation), tumor seeding (very rare), skin burns, bile duct stenosis, urinoma/ureteral injury, cryoshock (thrombocytopenia + hepatic/renal failure)

  • Ureteral injury risk with renal ablation: 25% within 1 cm, 10% within 1-2 cm; reflux of excreted contrast into the treatment bed shouldn’t happen unless there’s ureteral obstruction.

  • Nerve injury with renal ablation: mainly the genitofemoral along the anterior psoas, lateral femoral cutaneous (numbness), iliohypogastric (oblique muscle atrophy,  bulging flank syndrome), ilioinguinal; can hydrodissect to reduce risk

  • Nerve injury or pathologic fracture with palliative met ablation are very rare. Can use neuromodulation if high concern. None reported in OPus One study.

Minor adverse event (5-20%): small pneumothorax, transient hematuria, pain, fever, pleural effusion, minor bleeding, contrast reaction, transient hypotension

  • Bedrest for 1-2 hrs with ablation site down

  • Pain/nausea control, mIVF, can often discharge same day

  • Discharge instructions: avoid immersion in water 2-3d, resume normal activity in 7-10d

  • Good to discharge with NSAID to decreased inflammation

  • Follow up imaging with clinic visit

    • Often people do CT/MRI in 3-6 mo (thin peripheral enhancement is normal)

    • Normal for lesion to increase in size at 1-4 wks, be similar in size at 3 mo, and decrease in size by 6 mo if treated effectively

    • 2021 AUA guidelines for RCC considered ablation intermediate risk suggesting follow up imaging every 6 mo for first 3 yrs then annual and continuing beyond 5 yrs