Surgical Management of Colorectal Liver Metastases

The appearance of liver metastases during the evolution of a primary colorectal tumor is a bad prognosis. To prolong the patient's life, many therapies have been proposed, more importantly, chemotherapy.

Today, surgical resection is the only therapeutic option for cure, and attains survival curves at medium and long term, superior to those obtained by other treatments. Resection achieves survival rates of 26 to 45% at 5 years, while it is almost zero in those cases not resected.

Liver resection leads to low morbidity and mortality, close to 1% in specialized centers. It must be emphasized that out of all the patients with colorectal liver metastases, only 10 to 20% can be resected. Today, the challenge is to develop new startegies thatt combine surgical resection with techniques of tumor destruction such as RFA, cryotherapy, portal embolization, and new chemotherapy protocols, with the goal of making those lesions that are initially considered unresectable, resectable.


Principles of Curative Liver Resection

The techniques are divided into 'anatomical' or 'non-anatomical' resections.

Anatomical Resections

They follow the liver segmentation principles described by Couinaud. They are considered as minor, when less than 3 segments are resected, or major, when resection inludes more than 3 segments.

Non-Anatomical Resections

They include the resection of a portion of the liver independently of the liver scisures and glissonian pedicles. They refer mainly to metastasectomies. The liver resection depends on the size of the tumor.

Rules to Respect During Hepatectomy

Independently of the type of liver resection, one must follow these rules in order to avoid postoperative complications:

* Functional liver parenchyma preservation of at least 30% of the total liver mass, to avoid hepatic insufficiency.
* Limit blood loss, in order to avoid transfusions, because it is a known risk factor that favors recurrence.
* Respect the 1 mm margin, to reduce the risk of recurrence.
* Respecto glissonian pedicles destined to the remaining segments, to avoid segmental exclusion, ischemia and necrosis, and biliary fistulas.

Preoperative Patient Evaluation

Before even thinking on performing a liver resection, it is necessary a thorough oncologic examination, seeking other localizations, and also to verify the absence of contra-indications.

Regarding morphological tests, an abdominal US, CT and afterwards a MRI, allow to acquire a better knowledge regarding number of metastases, precise location, relationship with the portal pedicle and the hepatic veins.

Pulmonary localizations must be ruled out systematically, using CT examination. If these lesions are resectable, they dont constitute a contraindication to liver resection. The same goes for all of the extrahepatic metastases.

A colonoscopy is always performed to rule out recurrence, even if the primary tumor has already been resected. If necessary, a bone scan or a brain CT can be performed.

Regarding the blood chemistry, it consists of liver function tests, tumor markers, coagulation profile and clearance of green indocyanine test, which allows to better evaluate liver function, specially in those patients who received neoafjuvant chemotherapy or those with a preexistent liver pathology (hepatitis, cirrhosis).

Valid Indications and New Operative Strategies

A patient with liver metastases limited to one segment without extrahepatic dissemination is always a candidate for liver resection. The challenge for hepatobiliary surgeons is to achieve the necessary resources and strategies that allow the patients' benefit.

The liver surgical progress and the development of new surgical techniques, like RFA, cryotherapy, new radiological interventions such as portal embolization, and new chemotherapy drugs have permitted the elaboration of this new strategies, which make possible curative resections to patients initially considered unresectable. Patients can be divided into four groups:

1. Patients with a voluminous hepatic metastases in which resection leaves an insufficient amount of functional liver parenchyma.
2. Patients with bilobar metastases.
3. Patients with recurrence after resection.
4. Patients with a primary colorectal tumor and synchronous liver metastases.

Patients with a Voluminous Liver Metastases

Two alternative may be offered: Tumor downsizing with systemic or local chemotherapy, and hypertrophy of the future remaining liver (non-tumoral) by portal embolization.

* Downsizing: Bismuth et al, from the Paul Brousse Hospital in France, showed in a study with 53 patients presenting with liver metastases initially non-resectable, that the use of neoadjuvant chemotherapy with 5-fluorouracyl, folinic acid and oxalyplatin, achieved an adequate tumoral downsizing, with similar results as those patients initially resectable. (Ann Surg 1996; 224: 509-522).
* Portal Embolization: When resection is not viable due to insufficient functional liver parenchyma (usually left lobe), surgeons look for hypertrophy of the non-tumoral liver. Once embolization is performed, hypertrophy is evaluated 5-6 weeks after the procedure. If the future remaining liver is >30%, then hepatectomy can be performed.

Patients with Bilobar Metastases

Many therapeutic options have been described:

* Two-stage Hepatectomy including Portal Embolization: The success seen for one stage hepatectomies after portal embolization, lead surgeons to the two stage procedure. This strategy consists on a first stage of metastases resection in the future remnant, and embolization of the tumoral liver. On a second stage, a right hepatectomy is performed, which can be extended to segment 4, after an adequate hypertrophy is achieved.
* Two-stage Hepatectomy: Described by René Adam, consists on the resction of the majority of the metastases in a first stage. Then resection of the remaining lesions after acquiring liver regeneration. In between, patients receive chemotherapy.
* Hepatectomy associated to resection and tumoral destruction by local treatment: Here, the greater lesions are resected and the lesser ones are destroyed locally by either RFA or cryotherapy.
* Two-stage Hepatectomy after neoadjuvant chemotherapy: The goal is to achieve an adequate downsizing of the tumor that allows for a resection in a one-stage or two-stage procedure.

Patients with Recurrence after Resection

Surgery is the only curative option for these patients. It has been shown that patients with a liver recurrence isolated or associated with a resectable extrahepatic metastases, resection of all the tumoral tissue achieves an overall survival similar to patients without recurrence.

Resection of the recurrence turns the clock back to zero. In these cases, tumor destruction by RFA or cryotherapy extends the indications.

Patients with a Primary Colorectal Tumor and Synchronous Metastases

Surgical startegies remain controversial. Those who favor simultaneous resection, and those who oppose it, differ in terms of oncological basis, immunological techniques and patient comfort. Jaeck showed that there was no difference between the two approaches (Chirurgie 1999; 124: 258-263).



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