Kecheng Xu,M.D.,Lizhi Niu,M.D.,Ph.D.,Weibing He,M.D., Yisong He,M.D.,Jiansheng Zuo,M.D.

ABSTRACT
Background
The purpose of this study was to determine the safety and efficacy for the treatment of patients with hepatic colorectal metastases.

Methods
From 852 patients with different types of liver tumors treated by cryosurgery in a 5-year period, the authors evaluated the results of 326 patients with nonresectable hepatic colorectal metastases. Cryosurgery was performed under the guidance of ultrasound or CT percutaneously. Most of the patients received transarterial chemoembolization(TACE) after cryosurgery. Follow-up was obtained at 1 month and every 4 months thereafter postoperatively by assessment of liver function test results, tumor markers, liver ultrasonography, and abdominal CT. Some of the patients received follow-up with positron emission tomography-CT (PET-CT). For lesions suspicious of recurrence, an ultrasound-guided liver biopsy was performed for histologic study. Subsequent re-cryosurgery was performed if histology was positive cancer.

Results
All patients underwent a total of 526 sessions of cryosurgery. There were 201 patients who received single cryosurgery,151 patients underwent multiple cryosurgery for recurrent tumors in the liver and extrahepatic places. At 3 month after cryosurgery, CEA level in 197 (77.5%) of patients with elevated markers decreased to normal range. According to the imaging study, cryotreated lesions showed CR in 41 patients (14.6%), PR in 115 patients (41.1%)，SD in 68 patients (24.3%) and PD in 56 patients (20%). The recurrence rate was 47.2% during a median follow-up of 32 months (range, 7-61). The liver was main area of recurrence, 61% of which occurred in liver only and 13.9% in liver and some extrahepatic places. Extrahepatic recurrence was mainly seen in lungs and lymph nodes. The recurrence rate at cryosite, including at cryosite only as well as cryosite and the remaining area of liver, was only 6.4% for all cases.During a median follow-up of 36 months (7-62months), the median survival of all patient was 29 months (range 3-62months).196 patients (60.1%) have died and 130 patients are alive, with a median survival of 26 and 36 months, respectively. Overall survival was 78%, 62%,41%, 34% and 23% at 1, 2, 3, 4 and 5 year, respectively,after the treatment. Patients with tumor size less than 3 cm, tumor locatied in right lobe of liver, the lower CEA levels (<100 ng/dl) and post-cryosurgery TACE had higher survival rate. There was no significant difference in survival bases on tumor number, pre-cryosurgery chemotherapy and the timing of the development of metastases (synchronous vs. metachronous). Patients who underwent 2-3 procedures of cryosurgery had an increased survival as compared to patients who received one time of cryosurgery only.There was no intra-cryosurgery mortality. Common adverse effects were temporal pain, fever, increased liver enzyme and thrombocytopenia, which were generally self-limited without poor outcome. Severe adverse effects, such as hepatic bleeding, cryoshock, biliary fistula, iver failure, renal insufficiency and liver abscess were observed in 0.3%-1.5% of patients.

Conclusions
The percutaneous cryosurgery was a safe modality. Rather than an alternative to resection, this technique is to be regarded as a complement to hepatectomy and as an additional means to achieve tumor eradication when the total excision can not be accomplished.

Key words: hepatic colorectal metastases, hepatic cryosurgery, percutaneous cryosurgery,colorectal cancer

Hepatic metastases are the main causes of death in patients with colorectal carcinoma. Hepatic resection is the choice for the treatment of the liver cancer if metastases are confined to the liver and may achieve 5-year survival of 25% to 39% [1-4].Resectability is usually determined by the absence of extrahepatic metastases, a maximum of four lesions in the liver and the ability to obtain cancer-free resection margins[5].Therefore,only 10%-20% of patients with hepatic colorectal metastases are suitable for resection[6].For unresectable liver metastases, chemotherapy or chemoembolization are often used, but the outcome is poor. Median survival is around 12 months for unresectable hepatic colorectal metastases[7].

Cryosurgery recently has been applied for unresectable liver tumors, showing encouraging results[8-11]. Between March 2001 and February 2007, 1090 patients with malignant liver tumors were treated by cryosurgery in our hospital. There were 680 patients with hepatocellular carcinoma (HCC), 326 patients with metastases originating from colorectal carcinoma, and 84 patients with liver metastases from cancer of noncolorectal origin. This study describes the results of percutaneous cryosurgery for the treatment of unresectable hepatic colorectal metastases with the purpose of determining the efficacy and safety of this modality.

PATIENTS AND METHODS

Patients
Three hundreds and twenty-six patients with hepatic colorectal metastases were enrolled in this study. There were 243 men and 83 women with a mean age of 54.8 years (range,32-84).The characteristics of patients and tumor features were listed in Table 1.

Diagnosis of hepatic colorectal metastases was made by intraoperative finding during the colectomy ,and in the postoperative follow-up by the combination of both increased levels of tumor markers (CEA) and imaging pictures of a lesion on ultrasonography, computed tomography (CT) scan or magnetic resonance imaging (MRI) of the liver. There were 234 patient whose diagnosis was proved by liver biopsy. Liver metastases were synchronous in 65 cases (19.9%) and metachronous in 261 cases (80.1%). The tumors of all cases received a thorough investigation with regard to the presence of multiple nodules or to the presence of a large and/or ill-located tumor, comorbidity, and were considered as unresectable. The patients with extrahepatic metastases or liver failure were be excluded from this study.

Table 1 Characteristics of patients with hepatic colorectal metastases

Technique of cryosurgery
Cryosurgery was performed with Cryocare Operative System (Endocare, CA, USA ) which used the Joule-Thomson effect to cool the end of a cryoprobe in closed systems . In accordance with the gas coefficient and the dimension of the nozzle, different gaseous elements generate different thermal exchange events at the area close to the nozzle. Argon gas is used for cooling (_187°C), and helium is used for heating (67°C).

The probe was inserted percutaneously under ultrasound or CT guidance, and two freezing-thawing cycles by lesion were performed. We used mainly 2-mm or 5-mm probes and rarely a 10-mm probe according to the size of the tumor. Simultaneous use of two or more probes was used mainly for large lesions. Individual tumors may be frozen sequentially on a tumor-by-tumor basis or simultaneously. The time of freezing was dependent on the achievement of an "ice-ball," visible as a hypoechogenic area on the ultrasonography, exceeding 1 cm the diameter of the lesion. Thawing then was achieved by inputting helium during a period equivalent to the freezing time before a second freezing process was begun. Hemostasis of the insertion hole of the cryoprobe was obtained by Spongel application to the tract of the cryoprobe and by suture of the insertion site.

Transarterial chemoembolization (TACE)
After cryosurgery, 280 patients underwent 1-2 sessions of TACE within the period of 1-2 months. The chemotherapeutic agents for intraarterial infusion were the mixture of Lipiodol and doxorubicin, cisplatinum, 5-fluorouracil, mitomycin C. Sometime gelfoam was used as an embolization material.

Follow-up
Postoperative follow-up was obtained at 1 month and every 4 months thereafter by assessment of liver function test results, tumor markers, liver ultrasonography, and abdominal CT. Some of patients received follow-up with positron emission tomography-CT (PET-C). Efficacy of cryosurgery was evaluated according to the evolution of tumor size and tumor markers. Changes in tumor mass were measured according to The Response Evaluation Criteria in Solid Tumors (RECIST) protocol [12],which based on objective measurements of lesion size before and after treatment.Complete response(CR) means cryotreated lesion disappearance (scar) or less than 25% of original size.Partial response(PR) means a greater than 30 % decrease in the sum of the largest diameter of all targeted lesions. Stable disease (SD) means less than 30% decrease in the sum of the largest diameter of all targeted lesions. Progressive disease (PD) means an increase of greater than 20% in the sum of the largest diameter of all targeted lesions.

All radiologic studies were reviewed by the same radiologist with a expertise in hepatic imaging. For lesions suspecious of recurrence, an ultrasound-guided liver biopsy was performed for histologic study. Subsequent re-cryosurgery was performed if histology was positive cancer. A persistent nodule on radiologic imaging, without tumoral activity shown on PET-CT ,or with the reducing and normal tumor markers (CEA) ,or no changes in the absence of other treatment for an interval of at least 6 months since cryosurgery, was considered as a remnant. Tumor recurrence was estimated either by histologic examination of the liver,or by combination of size increase of the cryotreated lesion on ultrasound, CT or PET-CT imagings and increased tumor markers.

Statistical analysis
Survival was determined according to the Kaplan-Meier method. Comparison of survival rates was obtained with the log-rank test. A p value lower than 0.05 was considered statistically significant.
RESULTS
All patients underwent a total of 526 procedures of cryosurgery. There were 151 patients who underwent multiple cryosurgery for recurrent tumors in the liver and extrahepatic places (Table 2).

Table 2 The sites of repeat cryosurgery

Change of tumor marker
Increased CEA levels was observed in 254 patients (77.9%) at the time of the initial diagnosis. At 3 month after cryosurgery, CEA level returned to normal range in 197 (77.5%) of patients with elevated markers, and increased in 41 patients (16.1%). There were 16 cases (6.3%) who had no significant change of CEA levels.

Evolvement in tumor size
After cryosurgery, early increase in the size of lesions in relation to the freezing margin exceeding 1 cm beyond the limit of the tumor was a constant feature. Cryotreated lesions appeared as hypoechogenic or hypodense areas. CR was observed in 41 patients (14.6%), PR in 115 patients (41.1%)，SD in 68 patients (24.3%) and PD in 56 patients (20%). Two patients with complete response proved by histology and CT scan are presented in Figure 1,2.

Firgue 1 The imagings of liver of patient with hepatic colorectal metastase. Complete ablation of tumor proved by histology achieved after percutaneous cryosurgery.(A)MRI before cryosurgery.(B)During percutaneous cryosurgery under CT guidance.(C)Twelve months after cryosurgery

Figure 2 CT scan of a patient with hepatic colorectal metastases treated by percutaneous cryosurgery. The massive lesion showed a complete response to cryosurgery and TACE.(A)Before cryosurgery.(B) Eight months after cryosurgery and TACE

Tumor recurrence
The recurrence rate was 47.2% during a median follow-up of 32 months (range, 7-61). Recurrence patterns are presented in Table 3. The liver was the main area of recurrence, 61% of which occurred in liver only and 13.9% in liver and some extrahepatic places. Extrahepatic recurrence was mainly seen in lungs and lymph nodes. The recurrence at cryosite, including at cryosite only as well as cryosite and the remaining area of liver, accounted 15.3% of cases who had recurrence and 6.4% of all cases.

Table 3． Recurrence pattern at death or latest follow-up

Overall survival

During a median follow-up of 36 months (7-62months), the median survival of all patient was 29 months(range 3-62months).196 patients (60.1%) died during the follow-up and 130 patients (39.9%) are alive, with a median survival of 26 and 36 months, respectively. Overall survival was 78%, 62%,41%, 34% and 23% at 1, 2, 3, 4 and 5 years, respectively(fig 3). Patients with tumor ￡3 cm, tumor located in right lobe of liver, CEA level <100 ng/dl and post-cryosurgery TACE had higher survival rate. There was no significant difference in term of survival between number of the tumors, pre-cryosurgery chemotherapy and the timing of the development of metastases (synchronous vs. metachronous)(Table 4).

Table 4．Survival based on patient characteristics and tumor features

*p <0.01

To some extent,the survival was related to the number of cryosurgery procedure performed on the patients. Patients who underwent 2-3 procedures of cryosurgery had an increased survival as compared to patients who received one time of cryosurgery only. However, the patients who received cryosurgery of more than three had the lower survival(figure 3).

Figure 3．Patient survival after cryosurgery

Mortality and morbidity
The minor and major adverse effects of cryosurgery were seen in Table 5.A temporary pain in right-upper quadrant of abdomen and fever (about 38 C)were observed in about half of patients . An elevation of serum transaminase levels occurred in 124 patients and normalization of the values was observed within 14 days. There were 78 patients who had a diminution of the platelet count without poor outcome and there were only 4 cases received infusion of thrombocyte concentration. 20 patients, in whom 18 had subdiaphramatic liver tumor, had right pleural effusion, probably due to the irritative process beneath the diaphragm.

There was intra-cryosurgery mortality. Haemorrhage from a cryosurgery-treated lesion was seen in 5 patients ,in whom 3 died of the complication. One patient, who underwent cryosurgery for more than 50% of liver volume, died of hepatic failure . One patient who received cryosurgery for 8 large metastases, died of a cryoshock syndrome. Three patients suffered from biliary fistula which resolved with transhepatic drainage. Five patients had temporary renal insufficiency, which presented an increased blood urea nitrogen and creatinine levels for 3-7 days. Two patients developed bacterial hepatic abscess within cryosites and recovered with antibacterial agents and drainage. Two patients , whose age were 72 and 76 years old,respectively, died of acute myocardial infarction and severe arrhythmias apparently unrelated to cryosurgery.

There was a total of 19 patients who developed major adverse effects ,which resulted in death in a total of 7 patients.

Table 5．Adverse effects within 30 days after cryosurgery

DISCUSSION

Cryosurgery is a treatment in which tumors are frozen and then left in situ to be reabsorbed. Several publications reported the results of hepatic cryosurgery for treatment of hepatic colorectal metastases[13-16]. The survival after cryosurgery is probably inferior to that achieved by liver resection but the fact should be noted that most of the patients undergoing cryosurgery have unresectable tumors or more late stage of the disease. Current long-term follow-up study showed that cryosurgery is an important option for a wide range of unresectable hepatic colorectal metastases and provides the potential for long-term survival[17].

Up to now, the cryosurgery for most of the patients with hepatic colorectal metastases was performed during laparotomy, either as a single modality or in association with liver resection. Operative cryosurgery is still more invasive therapy to patient. As advancement of imaging guidance and improvement of cryosurgical apparatus, percutaneous mode of cryosurgery,a less invasive procedure, has been used for treatment of tumors, and apparently,may be suitable for unresectable hepatic colorectal metastases.

As to percutaneous cryosurgery, a great attention has been paid for its long-term efficacy and safety. Following is the discussion about the results of percutaneous cryosurgery in this study, we make a discussion.

Efficacy of percutaneous cryosurgery

This study, in which 326 patients with unresectable hepatic colorectal metastases who underwent percutaneous cryosurgery were followed-up for a median of 36 months, showed:
a) After cryosurgery, serum CEA in 77.5% of patients with elevated markers returned to normal range.
b) After cryosurgery, cryotreated lesions presented CR in 14.6% of patients, PR in 41.1%，and SD in 24.3%.
c) During a median follow-up of 36 months (7-62months), the median survival of all patient was 29 months (range 3-62months). Overall survival was 78%,62%,41%,34% and 23% at 1,2,3,4 and 5 years, respectively.

Comparing the results of operative cryosurgery reported in the world literature (Table 6),in which the median survival of patients after cryosurgery ranged 21-45 months, and the 1-,2-,3-and 5-year survival were 52%-86%,36%-62%,10%-70% and 5%-44%, our results in this study are encouraging, especially in terms of unresectability of tumor.

Table 6．Results of hepatic cryosurgery for colorectal metastases

* 30 month survival
**Including 56 cases of hepatic colorectal metastases
Cryo:Cryosurgery,OC:Operative cryosurgery，PC：Percutaneous cryosurgery

Similar to operative cryosurgery, the main problem in the face of percutaneous cryosurgery is recurrence of disease. In our patients, 47.2% had disease recurrence during a median follow-up of 32 months (range, 7-61 months). The liver was main place of recurrence, 61% of which occurred in liver only and 13.9% in liver and some extrahepatic places. Extrahepatic recurrence was mainly seen in lungs and lymph nodes. The overall recurrence rate is lower than 44% in a mean follow-up of 16 months reported by Adam [13] and is much lower than 78% reported by Weaver[16]. It is important to point out that in our patients the recurrence rate at cryosite, including at cryosite only as well as both of cryosite and the remaining place of liver, was only 15.3% for cases who had recurrence and 6.4% for all cases, which are significantly lower than 58.8% reported by Jungraithmayr[24]. Obviously, the decreased recurrence of tumor is related to better survival of patient.

Factors influencing survival of patient

This study showed that patients with lesions of 3 cm or smaller than 3 cm had an increased survival rate compared with those with lesions of more than 3cm,their median survival was 39 and 21 months, respectively. The reason could be the larger tumor in the vicinity of large vessels and the exposure to the heat sink effect. Blood flowing by with a warming effect can induce the insufficient cryodestruction for tumor. Pearson[25] reported 66.7% of local recurrence occurred directly in the venae cava (VC) or a large vessel. No significant correlation was found between the number of metastases and survival. Patients with tumor in right lobe in liver had higher survival compared with those in left lobe and bilobe, which could be explained by the fact that latter location are more closed to large vessels.

This study also appeared to show a correlation of poor survival with CEA levels over 100 ng/dl with a median survival of 18 months,is much less than 38 months median survival for the patients with lower CEA(p<0.01). The result is consistent to that reported by Weaver[15,16] who showed that patients with precryosurgery CEA >100 ng/dl had only 10 months of median survival, while the median survival of patient with CEA lower than the level was 17-19 months. The poor outcome of patients with higher CEA could be related to biological behavior of CEA-secreting tumor.

According to the experience in this study, the possibility of repeat cryosurgery percutaneously may be a factor which bring about better survival and low recurrence. Patients who received 2-3 procedures of cryosurgery for the tumor in the liver had higher survival. In contrast to operative cryosurgery, percutaneous cryosurgery may be performed in many times because of its convenience and mini-intervention. As a result, the recurrence in liver and extrahepatic metastases may be conveniently treated. In this series, there were 12 and 6 patients, respectively, with lung and pancreas metastases, which were treated by percutaneous cryosurgery as well.

As shown in this study, patients who received post-cryosurgery TACE had the higher survival compared to patients who didn’t received TACE(5-year survival of 47% vs 15%).Post-resection TACE has been proved to decrease the recurrence rate for patients with hepatocellular carcinoma[26]. The effect, therefore, may be an additional factor for the higher survival in our patients. We have used combination of percutaneous cryosurgery and absolute ethanol injection for treatment of HCC with good results[27].The strategy may be suitable for hepatic colorectal metastases.

Safety of percutaneous cryosurgery
In this study, a total of 526 procedures of cryosurgery in all patients were safely performed percutaneously. There were 105 patients who underwent repeat cryosurgery as many as 2-4 procedures for recurrent tumors in the liver and extrahepatic places. There was no treatment-related motality. Although about one third of patients presented adverse effects, such as pain, fever, increased liver enzyme, thrombocytopenia, and pleural effusion, they were generally self-limited without poor outcome. Cryoshock, as a most serious complication of hepatic cryosurgery, was observed in one patients in our series with incidence of 0.3%,which is lower than 1% in patients who underwent operative hepatic cryosurgery based on a world survey[28].Other major adverse effects, such as hepatic bleeding, biliary fistula, liver failure, renal insufficiency and liver abscess, were observed in 0.3%-1.5% of our patients, however, the incidence is no higher than that in patients who underwent operative hepatic cryosurgery[29]. Therefore, percutaneous cryosurgery for liver is a safe technique.

Conclusion
The results of this study clearly show that percutaneous cryosurgery was safe modality. Rather than an alternative to resection, the technique is to be regarded as a complement to hepatectomy and as an additional means to achieve tumor eradication when total excision can not be accomplished.

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