Radiofrequency Ablation (RFA)/Transarterial Chemoembolization (TACE)

Interarterial approaches: Transarterial chemoembolization (TACE), yttrium-90 radioembolization

Commentator: MICHAEL CHOTI, MD

Comment:

Few data show that TACE or standard chemoembolization therapy has any benefit for patients with colorectal metastases, so I would not recommend this therapy. The use of TACE therapy could potentially stress the liver. Colorectal metastases are typically not hypervascular, so we use TACE therapy for other forms of liver cancer that are vascular. But in this disease, it probably doesn’t contribute much. Indeed, it’s possible that TACE could stress or damage the liver, burning a bridge to other potential options, including further surgical therapy. The other problem is that it could delay therapy.

Another interarterial approach used selectively for some patients with unresectable colorectal metastases is interarterial yttrium-90 radioembolization, instead of chemoembolization. That is approved for metastatic colorectal cancer.

Perspective on role of radiofrequency ablation (RFA)

Commentator: MICHAEL CHOTI, MD

Comment:

RFA refers to the interstitial or intertumoral ablation of tumor most commonly using an electrical current to create a thermal ablation zone. Other methods of ablation include cryoablation, microwave ablation and other approaches. The most common ablation approach at this time is radiofrequency ablation.

RFA does not remove the tumor. The probe is typically placed in the desired zone using ultrasound guidance, and then a volume or sphere of thermal ablation destroys the area, which hopefully completely incorporates the tumor. It does not work well for larger tumors, and it is associated with a high local recurrence rate. RFA does not work as well in tumors that are close to large vascular structures, as in those that are further away. Risks associated with its use exist in tumors that are located near a main bile duct or other structure adjacent to the liver, because burning those areas can cause damage to the vital structures either within the liver or adjacent to the liver. So it has to be used carefully and selectively not to cause damage, and it is not always effective.

The goal of RFA should be complete destruction of the tumor. The goal of RFA is not palliation, it is the same as the goal of resection — complete negative margins. Using current technology, RFA is probably not quite as effective as resection. However, it still has a benefit. We generally reserve RFA for tumors that are unresectable but are in location and size that are candidates for ablation.

Perspective on the role of RFA

Commentator: NICHOLAS PETRELLI, MD

Comment:

The gold standard for treating hepatic metastasis in colorectal cancer is hepatic resection. The silver or the bronze standard is RFA. I would never use RFA with a patient who has a resectable lesion and is a candidate for surgery. Hepatic surgeons who don’t have the experience to perform hepatic surgery fall back on RFA, and that’s a disservice to the patient.

I think RFA is an option at times. For example, if you have numerous lesions, you may have to resect some and use RFA for others because you must leave functional liver behind. So you have to be careful. RFA is an option, but not with potentially resectable disease as long as you can leave functional liver behind, and maybe that’s the qualification. Because in general, you’ll end up taking out more functional liver with a resection than you will with an RFA. With RFA, there is a higher potential to leave more viable disease behind.

Clinical indications for RFA

Commentator: JOHN PRIMROSE, MD

Comment:

The use of RFA is controversial in colorectal liver metastasis — in hepatoma, the evidence base for its use is much clearer. For patients with colorectal liver metastasis, I do not feel RFA should be used if excisional surgery is feasible and safe. For instance, we use RFA for some elderly patients who are not eligible for open resection, and we sometimes use it for patients with recurrent disease after a resection, because we know that re-resections tend to be difficult to perform technically.

Perspective on the role of RFA

Commentator: ALAN VENOOK, MD

Comment:

Our philosophy is that RFA is the second choice to resection. In combination with resection, it’s something we’ll often use as an alternative for a patient that has bilobar disease with inadequate resection margins on each side of the liver.

It’s believed that in combination, for a lesion smaller than two centimeters, reliable margins are obtained with open RFA. On the other hand, as the tumor size increases to three, four or five centimeters, RFA is going to fail too often.

For example, with a small lesion in the left medial segment, under direct visualization with ultrasound, you may be confident with such an alternative. One of the things we do not perform is percutaneous ablation. Also, if in the eyes of the surgeon the patient has resectable disease, it’s important to reiterate that we don’t perform ablation.

Percutaneous ablation

Commentator: ALAN VENOOK, MD

Comment:

A lot of interventional radiologists have the technical ability and knowledge to perform percutaneous ablation. Percutaneous ablation is performed by ultrasound guidance through the skin. Our belief is that is unacceptable — the exception is a rare instance in which percutaneous ablation may be appropriate due to the failure rate that would be encountered without performing the procedure, such that much poorer visualization of the liver in the margin would be obtained. It’s a less evidence-based procedure that is generally performed by the interventional radiologist, and is not normally done at a larger tertiary center. Some oncologists believe that these willy-nilly ablations are helpful, but we simply view such ablations as totally unacceptable, except in rare instances where we’d consider it.

Surgical resection versus RFA

Commentator: AXEL GROTHEY, MD

Comment:

I’ve discussed the impact of a positive margin on prognosis with Steve Curley and he says that in a R1 hepatic resection for metastases, cauterization alone provides so much additional margin that the positive margin does not impact the local recurrence risk. Personally, I’ve yet to see a local recurrence after a resection for colon cancer, whereas I have seen local recurrences after RFA.

I believe we can reliably ablate hepatic lesions that are smaller than 1.5 or 2 centimeters. If the lesion is larger than two centimeters, then we know the overall outcome is much worse.

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