Role of thermal ablation in the management of colorectal liver metastasis

Abstract

With a recent randomized prospective trial revealing that thermal ablative therapy as local tumor control improved overall survival (OS) in patients with unresectable colorectal cancer liver metastases (CRLM), thermal ablation continues to remain as an important treatment option in this patient population. Our aim of this article is to review the current role of the ablative therapy in the management of CRLM patients. Main indications for thermal ablation include (I) unresectable liver lesions; (II) in combination with hepatectomy; (III) in patients with significant medical comorbidities or poor performance status (PS); (IV) a small (<3 cm) solitary lesion, which would otherwise necessitate a major liver resection; and (V) patient preference. There are several approaches and modalities for ablative therapy, including open, percutaneous, and laparoscopic approaches, as well as radiofrequency ablation (RFA) and microwave ablation (MWA). Each approach and ablation modality have its own pros and cons. Percutaneous and laparoscopic approaches are preferred due to minimally invasive nature, yet laparoscopic approach has more benefits from thorough intraoperative ultrasound (US) exam as well as complete peritoneal staging with laparoscopy. Similarly, whereas high local tumor failure rate has been a major concern with RFA, MWA or microwave thermosphere ablation (MTA) have demonstrated significantly improved local tumor control due to homogenous tissue heating, ability to reach higher tissue temperatures, and less susceptible to the "heat-sink" effect. Although liver resection is the standard of care for CRLM, there have been some retrospective studies demonstrating similar oncological outcome between ablative therapy and surgical resection in very selected populations with small (<3 cm) solitary CRLM. Lastly, ablative therapy and liver resection should not be mutually exclusive, especially in the management of bilobar liver metastases. Concomitant ablative therapy with hepatectomy may spare the patients from having two-stage hepatectomy with less morbidity. The role of the thermal ablation will continue to evolve in patients with resectable and ablatable lesions owing to newly emerging technology, in addition to new systemic treatment options, including immunotherapy for metastatic colorectal cancer (CRC).

Keywords: Thermal ablation; colorectal cancer liver metastasis (CRLM); microwave ablation (MWA); radiofrequency ablation (RFA).

Figure 1

Radiofrequency ablation (RFA) needle (A) used in our institution. The picture is 15 Gauge, 5 cm catheter. An intraoperative photo demonstrating the performance of RFA guided by intraoperative ultrasound (B). In our practice, two 12 mm trocars were placed in the right upper quadrant, one for the laparoscope and the other for the ultrasound probe. The RFA needle was placed percutaneously under direct visualization. An intraoperative photo demonstrating a laparoscopy/ultrasound picture in picture during the RFA (C).

Figure 2

An example for radiofrequency ablation (RFA). The patient is an 83-year-old female with metachronous liver metastasis from sigmoid colon cancer. During the surveillance 2 years after sigmoidectomy, the patient was found to have a lesion in the segment III. (A) Preoperative lesion (red circle), 1.39 cm × 1.30 cm on the segment III; (B) 3-month postoperative lesion; and (C) local recurrence medial to the previous ablation site in 15-month follow-up imaging.

Figure 3

Microwave thermosphere ablation (MTA) needle (A) used in our institution. The needle is 14 Gauge and 30 cm with saline circulation to cool off the antenna tip. An intraoperative photo shows the performance of MTA guided by intraoperative ultrasound (B).

Figure 4

An example for microwave thermosphere ablation (MTA). The patient is a 75-year-old male with synchronous liver metastasis from right side colon cancer. The patient underwent simultaneous laparoscopic MTA and right hemicolectomy. Green circle represents the targeted tumor, and red circle represents the anticipated ablation size (A). Preoperative lesion using the simulation software (B) 1-week follow-up image after MTA.

Figure 5

The trocar placement is similar to that in radiofrequency ablation (RFA) except for the use of an additional 3 mm trocar for the microwave thermosphere ablation (MTA) antenna, which is less rigid than the RFA needle. An intraoperative photo demonstrating a laparoscopy/ultrasound picture in picture during the MTA.