Radiofrequency Ablation (RFA)

Radiofrequency ablation (often abbreviated RFA) is a minimally invasive treatment for destroying tumors, including liver metastases of GIST. It involves insertion of a needle electrode into the tumor to heat and kill the tumor cells with radiofrequency energy. Imaging such as CT or ultrasound is used to guide the needle placement. Once the needle is in place, metal tines are deployed from the hollow core of the needle that penetrate and envelope the tumor. Radio waves are then transmitted to the needle tip and though the tines. These radio waves generate heat that “cooks” the tumor.

Radiofrequency ablation is not the same as ionizing radiation therapy used for tumors of the breast or prostate, etc. Radiofrequency ablation uses low-frequency radio waves that generate localized heat, not the destructive ionizing radiation given off by radioactive elements.

Because it does not require a large incision, it enables the patient to recover from the procedure much more quickly than abdominal surgery. RFA is an especially appropriate treatment for GIST patients who cannot tolerate surgery.

In treating GIST, RFA is applicable to relatively small liver tumors that are not close to blood vessels or ducts in the liver, as long as there are not too many tumors. It may also be useful in cases where a resistant clone is growing within a non-liver GIST (the “nodule-within-a-mass” phenomenon), while the remainder of the tumor is still controlled with imatinib or another drug.

Descriptions of RFA

Excellent descriptions and photos of radiofrequency ablation of liver tumors are available at this link:
RadiologyInfo.org
Additional links describing the procedure include these:

• National Institutes of Health
• Mayo Clinic

RFA Results in GIST

It is difficult to assess whether RFA is as effective as surgery in eradicating liver metastases because patients who are able to have surgery generally do not have RFA instead.  Thereore, comparisons are biased by patient selection.  A few medical papers address RFA effectiveness.

Pawlik et al (2006) at MD Anderson Cancer Center reported a series with 36 non-GIST sarcoma patients and 31 GIST patients who received RFA and/or surgical resection of liver metastases.  When surgical resection was possible, that was the first choice (35 patients).  RFA was used in combination with surgical resection of the largest lesions in 18 cases.  RFA was used alone in 13 cases. Those patients treated with RFA alone, or in combination with surgical resection, had a significantly higher rate of recurrence (90.9%) than did patients who underwent resection alone (57.1%).  However, this difference probably reflects a selection bias, since RFA was never used for patients whose tumors were resectable. Patients who were treated with RFA either alone or as a combined modality with resection also had a shorter disease-free interval (7.4 months) than patients who underwent resection alone (18.6 months).

Hasegawa et al (2007) reported three advanced GIST patients whose focal liver progression was successfully treated with RFA.  The patients remained progression-free at 8, 15, and 16 months after ablation.

In an ASCO poster presentation, Dileo et al (2004) reported treating 9 patients with percutaneous CT-guided RFA for single or limited site(s) of progressing disease (8 liver lesions and 1 soft tissue lesion). Thee were no complicaitons from the RFA procedure.  With median follow-up of 4.2 months (range 1-11 months), all patients had their lesions completely ablated. Five patients developed systemic progression, while 4 patients remain stable on continued treatment with imatinib (median follow-up 5.8 m). The authors concluded “In this small cohort, percutaneous RFA appears to be a safe and effective treatment for localized sites of progression. This procedure helps to manage limited IM-resistant GIST. Continuation of imatinib to control systemic sites of imatinib-sensitive GIST despite emergence of limited clonal resistance can be justified on the basis of this exploratory work.”

Evaluating the evidence about RFA for GIST, Avritscher and Gupta (2009) stated: “RFA appears to be a viable palliative option for patients with advanced GIST who develop focal progression of liver or peritoneal disease during imatinib therapy and who are not otherwise candidates for surgical resection. Alternatively, RFA offers a potentially curative option for patients who exhibit a partial response to imatinib and have focal residual disease that is not amenable to surgical resection.”

Avritscher R, Gupta S.
Gastrointestinal stromal tumor: role of interventional radiology in diagnosis and treatment.
Hematol Oncol Clin North Am. 2009 Feb;23(1):129-37, ix.  PubMed PMID: 19248976.

Hasegawa J, Kanda T, Hirota S, et al.
Surgical interventions for focal progression of advanced gastrointestinal stromal tumors during imatinib
therapy.
Int J Clin Oncol 2007;12:212–7.  PMID: 17566845

Higgins H, Berger DL.  RFA for Liver Tumors: Does It Really Work?
Oncologist 2006;11;801-808,  DOI: 10.1634/theoncologist.11-7-801
Free access at this link:  http://theoncologist.alphamedpress.org/cgi/content/full/11/7/801

Pawlik TM, Vauthey JN, Abdalla EK, et al.
Results of a single-center experience with resection and ablation for sarcoma metastatic to the liver.
Arch Surg 2006;141:537–43 [discussion: 543–34].
free access at this link: http://archsurg.ama-assn.org/cgi/content/full/141/6/537