Ultrasonic characteristics of frozen liver

Hepatic cryosurgery for liver metastases. Long-term follow-up

OBJECTIVE

The aim of this prospective study was to evaluate the applicability of cryogenic and conventional surgery in treating liver metastases (LM) with respect to intraoperative tumor reduction and survival rate.

SUMMARY BACKGROUND DATA

As have been shown in animal experiments as well as in clinical investigations, cryosurgery has been used for the treatment of many benign and malignant conditions. For the first time, this report summarizes a 10-year follow-up clinical experience with cryosurgery for treatment of LM from 1983 to 1992.

METHODS

One hundred twenty-three patients with LM (87 males and 36 females, a ratio 2.4:1.0; age, 41.3 +/- 12.1 years) were stratified and entered into a long-term prospective, randomized clinical trial for cryogenic surgery in group 1 (n = 63) and conventional surgical techniques in group 2 (control subjects, n = 60). Principally, a self-constructed cryogenic clamp was used for hepatic cryoresection with preliminary freezing of the margin resection by a cryosurgical system "Cryoelectronic-2" or "Cryoelectronic-4". Hepatic cryoextirpation (cryoablation) and hepatic cryodestruction were performed by means of probes of different roughly disk design from phi 5 mm to 55 mm by volume of frozen zone of 40 cm3 to 180 cm3 for approximately 7 to 32 minutes.

RESULTS

In most cases in group 1 and group 2, LM were based on colorectal cancers (65% vs. 68%). The hepatic cryosurgical procedures in group 1 included cryoextirpation (29 patients, 46%), cryoresection (20 patients, 32%), and cryodestruction (14 patients, 22%) solely. Clinical and laboratory parameters showed that the curative effects were significantly higher in group 1 than in group 2. The 3-year survival rate was in group 1 and group 2 (60% vs. 51%, respectively). The 5-year survival rate was 44% in group 1 and 36% in group 2. Twelve patients (19%) versus 5 patients (8%) in group 1 and group 2, respectively, survived 10 years. The disease-free survival was in group 1 and group 2 (30% vs. 18%, respectively). During a follow-up period, recurrence in the liver was observed in 54 patients (85%) in group 1 and in 57 patients (95%) in control subjects. After a 10-year follow-up period in group 1 and group 2, 9 patients (14%) versus 3 patients (5%) remained disease free, 3 patients (4%) versus 2 patients (3%) were surviving with disease, and 51 patients (81%) versus 55 patients (92%) died.

CONCLUSIONS

The data of this 10-year prospective, randomized clinical trial suggest that hepatic cryosurgery is effective in the treatment of resectable and nonresectable LM. The results show intraoperative tumor reduction (> or = 90% < or = 97%) and extended higher survival in these patients. The study indicated a 5-year and 10-year survival rate of 44% and 19% after cryosurgery, respectively.

Effect of thermal variables on frozen human primary prostatic adenocarcinoma cells

OBJECTIVES

Recent advances in imaging technology and cryotechnology have rekindled interest in prostate cryosurgery. Cryosurgery, however, cannot be applied precisely without knowing how the thermal variables used during the procedure affect tissue destruction. The goal of this article is to provide quantitative values for the relationship between thermal variables during freezing and the destruction of human primary prostatic adenocarcinoma cells.

METHODS

Human primary prostatic adenocarcinoma cells were frozen with controlled thermal parameters, using a directional solidification apparatus. Cell viability was determined after thawing, using trypan blue and a two-dye fluorescent test and correlated to the thermal variables used during freezing.

RESULTS

Human primary prostatic adenocarcinoma cells are damaged by intracellular chemical damage when frozen with cooling rates lower than 5 degrees C/min and by intracellular ice formation when frozen with cooling rates higher than 25 degrees C/min. A double freeze/thaw cycle is required to ensure complete cell destruction at high subzero temperatures, which must be lower than -40 degrees C for the low cooling rates and lower than -19 degrees C for the higher cooling rate.

CONCLUSIONS

Haphazard freezing does not necessarily destroy tissue during cryosurgery; however, quantitative data on the relation between thermal variables and frozen cell destruction can provide the means for performing cryosurgery more precisely and with greater control over the outcome of the procedure.

Cryosurgical ablation of unresectable hepatic tumors

Ultrasound-guided hepatic cryosurgery is a potential treatment option for select patients with unresectable tumors. Intraoperative placement of cryoprobes and monitoring of tumor freezing with ultrasonography produce complete remission in 22% to 29% of patients with unresectable metastatic colorectal tumors to the liver. Perioperative nurses should be knowledgeable about cryosurgical techniques and be prepared to participate in this innovative treatment modality to provide optimal care to surgical patients.

A comparative assessment of cryosurgical devices: application to prostatic disease

OBJECTIVES

To determine the comparative freezing ability of the Cryotech (CT) and AccuProbe (CMS) cryosurgical systems.

METHODS

Four conditions designed to model clinical situations were produced: (1) Single-probe performance in water at 17 degrees C; (2) five-probe performance in water at 17 degrees C; (3) single-probe performance in gel at 22 degrees C; and (4) single-probe performance in bovine liver. Parameters evaluated included temperatures at various time points (rates to and final low temperature), configuration of a freeze zone, and shaft freezing characteristics. In addition, isotherms were measured at predetermined distances from the center of the freeze zone.

RESULTS

Both systems provided freezing of various media under operational conditions. In water, the CMS 3-mm probe delivered more rapid freezing temperature rates than the 3-mm CT probe, with a 110 degrees C difference in probe surface temperature. In gel, the CMS probe increased freeze volume fourfold versus a twofold increase for the CT probe. In bovine liver, there was nearly equivalent performance with respect to geometry of the freeze ball. Extrapolation of the CT cooling curve indicated temperature equivalence at 30 minutes. A larger shaft diameter 4.9-mm CT probe produced results similar to the CMS probe in all the tested media. In addition, the freeze configuration of the CMS probe was spherical; the CT configuration was more cylindrical. CMS probe (equivalent diameter) tip temperatures were on average 100 degrees C lower.

CONCLUSIONS

Our tests demonstrated differences between the CMS and CT probe. The major differences are in the configuration of the freeze zone and shaft freezing. In equivalent conditions, the CMS 3-mm probe delivered more rapid cooling rates, a more spherical freeze ball, and lower absolute temperatures than the CT 3-mm probe. The larger CT probe produces equivalent freezing temperatures to the CMS probe, albeit with a more spherical shape. However, these in vitro systems may not adequately reflect varied prostate morphology. Further research is under way to determine if these differences affect relative efficacy of cryotherapy of the prostate.

Ultrasound characteristics of renal cryosurgery

The ability to visualize renal cryosurgery using ultrasound was tested in an animal model. Five dogs underwent open laparotomy and ultrasound-monitored cryosurgery of both kidneys. On each kidney two cryolesions were made. The borders of the frozen region were identified on ultrasound as a hyperechoic rim created by the interface between frozen and unfrozen tissue. The thawed cryolesion appeared hyperechoic compared with the unfrozen kidney. Excellent correlation between the ultrasound and autopsy measurements of the cryolesions was obtained. Knowing this, renal cryosurgery under ultrasound monitoring may be possible.

Cryosurgery of liver cancer

Cryosurgery, the in situ destruction of tissue using subzero temperatures, has been used to treat hepatic metastases. Because it is a focal treatment, cryosurgery can be used in patients with unresectable lesions due to location (next to major blood vessels) or multiplicity. In this study, 57 patients with unresectable hepatic metastases were treated with cryosurgery (with at least a 6-month follow-up). The number of lesions treated ranged from 1-16 with a mean of 4.6. Forty-three patients (73%) had bilobar disease, while 25 patients (42%) were treated with a combination of resection and cryosurgery. The disease-free survival rate (patients with normal computed tomography [CT] scans and carcinoembryonic antigen [CEA] levels) was 27% with a mean follow-up of 21 months. This is comparable to other hepatic cryosurgery studies that have found survival rates of 25-37.5%. Although the results are still short-term, this study indicates that hepatic cryosurgery offers the hope of long-term survival in patients with unresectable hepatic metastases.

Percutaneous transperineal prostate cryosurgery using transrectal ultrasound guidance: animal model

Cryosurgery has previously been used successfully to treat prostatic carcinoma. Inability to monitor the freezing led to local complications that limited the use of this modality. Recent studies have shown that monitoring of the freezing process can be accomplished using real-time ultrasound. In this study, transrectal ultrasound guidance was used to guide a cryoprobe percutaneously, using a transperineal approach, into the prostate. The extent of freezing was then monitored using ultrasound, taking care not to freeze the urethra or the rectum. Six dogs had the procedure without any complications. This study demonstrates the feasibility of a noninvasive treatment for prostatic carcinoma.

Ultrasound-guided hepatic cryosurgery in the treatment of metastatic colon carcinoma. Preliminary results

Cryosurgery, the in situ freezing of cancer, has been proposed in the past as a possible treatment for unresectable hepatic tumors. Its advantage lies in the fact that it is a very focal treatment sacrificing less normal tissue than surgical resection, allowing treatment of multiple lobes. Because cryosurgery does not affect large vessels, tumors in difficult locations, such as adjacent to the inferior vena cava (IVC), can be treated. With the use of intraoperative ultrasound to place the cryoprobes and monitor the freezing process, 18 patients with unresectable metastatic colon carcinoma confined to the liver were treated. Of the 18 patients treated, 4 (22%) are in complete remission as determined by computed tomography (CT) scans and carcinoembryonic antigen (CEA) levels, with a mean follow-up of 28.8 months. Four patients (22%) were not adequately treated at the time of cryosurgery. The number of lesions frozen in each patient ranged from 1 to 12, with a mean of 6 lesions. Fourteen patients had bilobar disease; three patients had previous right lobectomies with recurrences in their remaining left lobes prior to cryosurgery, and one patient had unilobar disease. Mean survival of the 14 cases with recurrence was 21.4 months, with 2 of the 14 still alive. Ultrasound-guided hepatic cryosurgery appears to be an effective treatment for metastatic colon carcinoma to the liver that is unresectable (including patients with bilobar and multiple lesions). These preliminary results indicate that the procedure warrants further study.

Cryolumpectomy for breast cancer: an experimental study

The effects of cryosurgical procedures and surgical excision in preventing the local recurrence of mammary adenocarcinoma were studied in BALB/cfC3H mice carrying syngeneic, virus-induced mammary adenocarcinomas transplanted into the fourth mammary fat pad. In this report we present evidence demonstrating that cryosurgical procedures involving multiple freeze-thaw cycles followed by tumor excision markedly reduce the local recurrence rate of mouse mammary cancer. Surgical resection without cryotreatment resulted in an 80% local recurrence rate; in contrast, cryotreatment consisting of three freeze-thaw cycles before excision prevented local tumor recurrence in 70% of the animals. The use of cryotherapy and local excision (cryolumpectomy) in the treatment of human breast cancer is discussed.

Real time ultrasonic monitoring of hepatic cryosurgery

Cryosurgery has a number of advantages that make it particularly appealing in the treatment of liver cancer. However, a major problem in the clinical application of hepatic cryosurgery is the lack of a precise means of monitoring the freezing process in situ. Preliminary investigations on simulated tissue have shown that standard ultrasonography is capable of accurately determining the amount of frozen material during a cryosurgical procedure. To extend these results to living tissue, cryosurgery was performed, in vivo, on the livers of four mongrel dogs. An ultrasound imaging device using a new intraoperative ultrasound transducer monitored the entire process in real time. The results indicate that the entire freezing and thawing cycle can be monitored easily using real time ultrasound. During freezing, the solidification interface can be seen to move through the tissue allowing clear imaging of the cryolesion. After complete thawing, the cryolesion became less echogenic than before freezing and was therefore distinguishable under ultrasound. Postsurgical pathologic examination showed excellent correlation between the lesion size and its ultrasonic image.