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1 All authors: Department of Ultrasound, Chinese PLA General Hospital, 28 Fuxing Rd., Beijing, 100853 China.
Received March 25, 2002;
accepted after revision October 29, 2002.
Address correspondence to B. Dong.
Abstract
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SUBJECTS AND METHODS. Survival rates were determined in 234 patients with 339 nodules of hepatocellular carcinoma who had undergone percutaneous microwave coagulation therapy (208 men, 26 women; mean age, 54.8 years; mean tumor size, 4.1 ± 1.9 cm; range, 1.2-8.0 cm; mean follow-up period, 27.9 months). Patients were those who had been rejected as candidates for surgery by the surgery department, who fit our study's criteria, and who agreed to participate. After baseline imaging studies were performed, the patients were followed up using the same combination of imaging (sonography, CT, or MR imaging) and posttreatment biopsy.
RESULTS. After percutaneous microwave coagulation therapy, color Doppler flow signals disappeared in 92.0% (263/286) of the lesions. No enhancement was apparent in 89.2% (190/213) and 89.1% (41/46) of the lesions on contrast-enhanced CT and MR imaging, respectively. Posttreatment biopsies of 194 nodules showed no evidence of surviving tumor tissue in 180 nodules (92.8%). Resections of six lesions revealed complete tumor necrosis in five. The 1-, 2-, 3-, 4-, and 5-year cumulative survival rates were 92.70%, 81.60%, 72.85%, 66.37%, and 56.70%, respectively. The relationships between survival curves and the degree of hepatocellular carcinoma tumor differentiation and between survival curves and tumor size were statistically significant (p = 0.021). No severe complications were seen.
CONCLUSION. Sonographically guided microwave coagulation proved to be safe and effective for the treatment of hepatocellular carcinoma. This therapy resulted in a high percentage of cases without evidence of residual tumor and satisfactory long-term results.
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Sonographically guided percutaneous microwave coagulation therapy is one of the relatively new thermal ablation modalities that are being used for the treatment of focal liver tumors. In 1994, Seki et al. [1] first reported percutaneous microwave therapy as an effective method for the treatment of small (< 2 cm) hepatocellular carcinomas. Its satisfactory therapeutic effect and good short-term results for treatment of small hepatocellular carcinomas have been reported by many investigators since then [2, 9, 10, 11, 12]. However, until last year, the efficacy of percutaneous microwave coagulation therapy for tumors larger than 2 cm and its long-term follow-up results had not been well confirmed. Our study, covering the long-term follow-up of 234 patients with 339 nodules, was undertaken to evaluate the clinical results and long-term therapeutic efficiency of percutaneous microwave coagulation therapy in hepatocellular carcinoma for lesions larger than 2 cm. This report is an expansion of our previous study [2].
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Two hundred forty-six patients with hepatocellular carcinoma were treated with percutaneous microwave coagulation therapy from May 1994 to July 2001 and then followed up continuously until December 2001. Twelve patients were lost to follow-up and were excluded. Thus, the total number of patients studied was 234. The study group included 208 men and 26 women, with an average age (± SD) of 54.8 ± 11.4 years (range, 25-81 years). Of these 234 patients, 33 patients (14.1%) preferred percutaneous microwave coagulation therapy as the initial therapy despite having operable hepatocellular carcinomas. The remaining 201 patients (85.9%) were not candidates for surgical resection because of one or more of the following conditions: poor liver function in 99 patients, advanced age with chronic kidney or heart disease in 25, multiple lesions located in different hepatic segments in 53, recurrent hepatocellular carcinomas (lesions that developed after curative resection of an initial lesion) in 31 patients, and unsuccessful transcatheter arterial embolization in 43 patients. The distribution of tumors by size and the number of tumors per patient are shown in Table 1. The diameter of the lesions at the widest point ranged from 1.2 to 8.0 cm (average, 4.1 ± 1.9 cm).
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Histologic diagnosis was confirmed by sonographically guided biopsies with an 18-gauge cutting biopsy gun. Specimens obtained through biopsy were assessed by two pathologists independently without prior knowledge of the cases. The histologic grades of differentiation were defined as follows: well differentiated, corresponding to Edmondson's grade I or I–II; moderately differentiated, corresponding to Edmondson's grade II or II–III; or poorly differentiated, corresponding to Edmondson's grade III or IV [13]. Histologic grading was obtained in 229 patients. There were 68 (29.69%) well-differentiated tumors, 104 (45.41%) moderately differentiated tumors, and 57 (24.89%) poorly differentiated tumors. Of the 234 patients, 95.9% patients had histologically proven liver cirrhosis. The severity of liver dysfunction was classified as Child class A in 24 patients (10.3%), Child class B in 207 (88.5%), and Child class C in three (1.3%).
As a general rule, patients who had uncontrollable ascites or a marked tendency to bleed (prothrombin activity < 40%, prothrombin time > 25 sec, platelet count < 50 cells x 109/L) were excluded from this study. For patients who had ascites, percutaneous microwave coagulation therapy was usually performed after ascites had been controlled by the administration of diuretics and albumin supplements.
Equipment
Microwave coagulator.—We used a microwave system with a
microwave frequency of 2450 MHz and a range of power output of 10–80 W
(UMC-I Ultrasound-Guided Microwave Coagulator, Institute 207 of the Aerospace
Industry Company, Beijing, China, and Department of Ultrasound of Chinese PLA
General Hospital, Beijing, China). The system was equipped with a low-lose
cable and a needle electrode (1.4 mm in diameter) with a surface coating to
prevent tissue adhesion.
Thermal monitoring system.—This system consists of a computer, a data acquisition module (HP34970A, Agilent Technologies, Palo Alto, CA), and iron-constant thermocouple needles. Iron-constant thermocouples were inserted and fixed into a 20-G percutaneous transhepatic cholangiography needle sheath with naked tips of 5 mm to measure the temperature. Data acquisition with a 16-bit analog output function was used; the maximum rate of data acquisition was 600 acquisitions per second on a single channel, and the scanning rate was up to 250 channels per second. The data acquisition unit was connected to a computer through an RS-232 interface to monitor the temperature dynamically.
Sonography system.—A 128 XP10/ART unit (Acuson, Mountain View, CA) and an HDI 5000 unit (ATL, Bothell, WA) were used in the study.
Ablation procedure.—Before treatment began, a detailed plan for the placement of electrodes, the power output setting, and the emission time was established on a tumor-by-tumor basis. In tumors with feeding blood vessels defined on color Doppler sonography, we placed the electrode in the vessels to destroy them before the ablation procedure, and we used a high-energy output setting (75 W for 180–300 sec). Success was defined as the disappearance of a feeding vessel's blood flow signal on color Doppler sonography after the procedure. All 109 feeding blood vessels in 78 patients were successfully destroyed at a thermal dosage of 75 W and an emission time of 180–300 sec.
In our study, if the diameter of a tumor was D mm, the diameter of the designated microwave coagulated area needed to be (D + 10) mm. With our microwave system, the maximum width of coagulated tissue volume using a single electrode at different outputs (60 W, 300 sec; 50 W, 10 min; 40 W, 30 min) varied from 2.6 to 3.4 cm and from 3.4 to 4.7 cm with double electrodes in vivo. For nodules smaller than 1.7 cm in diameter, only one insertion was required; for nodules 1.7 cm or larger, multiple insertions were needed.
In our study, one electrode in the center of the tumor was applied for tumors smaller than 1.7 cm. Two electrodes were used for tumors 1.7–3.0 cm with an interlectrode distance of 1.4–1.6 cm. For tumors larger than 3.0 cm, three or four insertions were made with an interelectrode distance of 1.4–1.6 cm (Fig. 1). The maximum distance setting of 1.4–1.6 cm between electrodes was based on computer simulation.
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Multielectrode ablation was always performed simultaneously within the same tumor. Findings from previous studies show that a larger volume of coagulated tissue can be obtained with the same energy output when multiple electrodes are implanted to the same depth and activated simultaneously than can be obtained when multiple electrodes are activated at different times [14].
An IV route was routinely established in all patients. After local anesthesia was induced with 1% lidocaine, a 14-gauge 15-cm guide needle with a sheath was inserted and positioned at the designated place of the tumor under sonographic guidance, then the stylet of the guide needle was pulled out. After the microwave electrode was introduced through the sheath of the guide needle, the sheath was withdrawn approximately 4–5 cm while keeping the electrode needle at its place to ensure that a portion of at least 4 cm from the tip of the electrode was exposed. The electrode was connected to the microwave coagulator through a flexible low-lose IV cable. Before the energy application was started for the multiple insertion treatment, two IV anesthetics were administered in all patients: propofol (Diprivan, Zeneca Pharmaceuticals, Wilmington, DE) combined with ketamine.
Because the largest coagulated dimension along the electrode is approximately 4.8–5.0 cm for one electrode placement in vivo, to achieve complete destruction of tumors larger than 4 cm, we first positioned the tips of the electrodes in the deepest part of the tumor. After the deep portion of the tumor was coagulated, the electrodes were withdrawn approximately 1.5–2.0 cm to ablate the superficial portion of the tumor.
In general, we used an output setting of 60 W for 300 sec for the treatments. For some tumors, a prolonged application (300–800 sec) of energy (60 W) was used depending on the temperature change displayed on the monitor in real time.
Assessment of Efficacy
Therapeutic efficacy was assessed on the basis of changes detected using a
combination of evaluations including imaging, posttreatment biopsies, and
-fetoprotein levels.
Sonographic scans were obtained in all patients at 3, 7, 14, and 30 days after percutaneous microwave coagulation therapy and thereafter at 1- month intervals by two independent radiologists who were unaware of the treatment sessions. Tumor size was recorded in three dimensions before and after percutaneous microwave coagulation therapy. Hypoechoic areas found in the treatment area, especially round areas with blood flow inside, were considered to represent local recurrence or incomplete necrosis.
Contrast-enhanced CT was performed in 160 patients with 242 nodules. CT scans were obtained before and after percutaneous microwave coagulation therapy on a helical CT unit (Tomoscan SR 7000, Philips Medical Systems, Best, The Netherlands). All helical CT scans were obtained with a section thickness of 5–10 mm, a collimation of 10 mm, a 1:1 pitch (table speed, 10 mm/sec), 120 kV, and 250 mA. Dual-phase enhanced scans were obtained: a power injector administered 100 mL of a 60% contrast agent (iopromide, Ultravist 300, Schering, Berlin, Germany) at a rate of 3 mL/sec. Patients underwent CT at 1 month and at 3 months after percutaneous microwave coagulation therapy and thereafter at 6-month intervals. Each CT image was assessed by two radiologists who did not know the therapy procedure. Well-defined nonenhancing tissue on images obtained during phases of contrast-enhanced CT was considered to represent necrotic tissue, and contrast enhancement in the treatment region indicated local recurrence or incomplete necrosis [15].
Contrast-enhanced MR imaging was performed in 33 patients with 49 nodules. MR images were obtained with a torso surface coil. MR imaging studies were performed on a 1.5-T unit (Advanced Signa, General Electric Medical Systems, Milwaukee, WI). The following sequences were used: spin-echo T1-weighted (TR/TE, 500/15; matrix, 256 x 192; 2 signals acquired); fat-suppressed fast spin-echo T2-weighted (4000/102; matrix, 256 x 256; 3 signals acquired); and fat-suppressed spin-echo T1-weighted (500/15; matrix, 256 x 192; 2 signals acquired) if the lesion presented as a high-signal-intensity area on a conventional T1-weighted sequence. A subsequent bolus injection of gadopentetate dimeglumine (Magnevist, Schering) was administered at a standard dosage (0.1 mmol/kg), and fast multiplanar spoiled gradient-recalled acquisitions in steady-state sequences (125/4.2; flip angle, 90°; matrix, 256 x 192; 1 signal acquired) were performed dynamically. Finally, spin-echo T1-weighted (500/15) and fat-suppressed spin-echo T1-weighted (TR range/TE, 500–600/15) sequences were performed. Hypointense nonenhancing tissue on gadolinium-enhanced T1-weighted MR imaging was indicative of tissue necrosis [3, 7, 16, 17].
Biopsies were performed after treatment with an 18-gauge cutting needle to maximize the sample and to increase accuracy under sonographic guidance in a high proportion of patients who consented to this procedure within 1–3 months after percutaneous microwave coagulation therapy in the early years of the study, because within 3 months after percutaneous microwave coagulation therapy it was difficult to identify complete necrosis using imaging methods (CT or MR imaging). In the 3 most recent years of this study, posttreatment biopsies were mainly used when a definitive judgment could not be made from the imaging data. Three to five specimens from different parts of the tumor were obtained from each patient. The specimens were assessed by two pathologists. In six patients, tumors were removed by surgical procedures 2–12 months after percutaneous microwave coagulation therapy.
Blood samples were assayed to determine the serum -fetoprotein level
and liver function before percutaneous microwave coagulation therapy and
2–4 weeks after percutaneous microwave coagulation therapy. After
percutaneous microwave coagulation therapy, if the results showed an abnormal
serum -fetoprotein level and abnormal values for liver function,
subsequent checks were performed at an interval of 2–3 months.
If feasible, another treatment was performed when a tumor recurrence was confirmed on imaging (sonography, CT, or MR imaging) or at posttreatment biopsy.
Thermal Monitoring
During the ablation procedure, the temperatures of the coagulation area
were monitored dynamically for patients who consented. In our study, a dynamic
temperature monitor was used in 118 patients; temperatures at 307 spots were
monitored altogether. After electrode insertion, one to three thermocouple
needles were introduced into the designated sites through an 18-gauge needle
sheath under sonographic guidance. Generally, thermal needles were positioned
in different places 5 mm outside the tumor, where we expected the margin of
the coagulated area to be. Temperatures in these sites were monitored
dynamically using our multichannel temperature monitor
(Fig. 1). The temperatures at
the tumor margin were used as an objective indicator for evaluating the effect
of the microwave treatment. Microwave radiation was terminated when the
temperature reached 60°C or stayed at 54°C for 3 min. At this
temperature, tissue was completely coagulated
[14]. If the temperature of
these sites had not reached the coagulated temperature of 54°C by the end
of the treatment session, we continued the energy application for a prolonged
period, up to 800 sec. Although the displayed temperature might be
insufficient to confirm whether the whole tumor was destroyed, it helped us to
determine thermal efficiency dynamically and to control the energy application
on individual bases in real time.
Statistical Analysis
Patient age and tumor size are expressed as mean ± SD. Cumulative
survival rates were calculated using the Kaplan-Meier method. The differences
between survival curves of the various groups were calculated using a
generalized Wilcoxon's rank sum test. A chi-square test was used to compare
the tumor recurrence rate among groups. A p value of less than 0.05
was considered a statistically significant difference.
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The survival curves of patients with poorly differentiated hepatocellular carcinoma tumor versus the survival curve of patients with well-differentiated hepatocellular carcinoma and of poorly differentiated hepatocellular carcinoma versus moderately differentiated hepatocellular carcinoma differed significantly (p = 0.021) (Fig. 3). However, the difference in the survival curves of patients with moderately differentiated hepatocellular carcinoma and those with well-differentiated hepatocellular carcinoma was not significant. As shown in Figure 4, our results reveal that differences in survival curves between patients with hepatocellular carcinoma lesions larger than 5 cm in diameter and those with hepatocellular carcinoma lesions 5 cm or smaller were significant (p = 0.021). There were no statistical differences (p > 0.05) between survival curves of patients with tumor lesions 3–5 cm and those of patients with tumor lesions 2–3 cm. The same pattern held for the groups with lesions that were 2–3 cm and those with lesions smaller than 2 cm.
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Changes in Images After Percutaneous Microwave Coagulation
Therapy
Sonographic examination soon after microwave-generated irradiation showed
an increasingly hyperechoic area with a posterior acoustic shadow that
appeared around the electrode. This hyperechoic area diffused along the
electrode with time and was concentrated in the tumor if the tumor had a
capsule. These changes were visible on sonographic images but diminished
rapidly as soon as the microwave generator was switched "off" and
completely disappeared within 8 hr. Sonographic findings were stable after 24
hr. After microwave therapy, the type of changes that occurred on the
sonographic images depended on the initial sonographic pattern. In our study
group, hypoechoic tumors increased in echogenicity, and hyperechoic lesions
became heterogeneously hyperechoic in most cases (Figs.
5A and
5D). Four weeks after
treatment, the lesions began to shrink. By the time 3 months had elapsed since
the procedure, the mean maximum diameters of the lesions had decreased to 3.5
± 1.7 cm, whereas the mean maximum diameters had been 4.1 ± 1.9
cm before therapy. Overall, 67.6% (229/339) of the tumors decreased in size
within 3 months after percutaneous microwave coagulation therapy.
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Color flow signals on sonography were detected in 286 (84.4%) of the 339 nodules before treatment (Figs. 5B and 5C). After treatment, color flow signals disappeared in 263 (92.0%) of those 286 nodules (Fig. 5D).
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Two hundred thirteen (88.0%) of 242 nodules and 46 (93.9%) of 49 lesions showed enhancement on contrast-enhanced CT (Fig. 6A) and contrast-enhanced MR imaging (Figs. 7A and 7B), respectively, before treatment. After treatment, enhancement within the tumor was not evident in 190 (89.2%) of 213 lesions on contrast-enhanced CT (Fig. 6B) and in 41 (89.1%) of 46 nodules on contrast-enhanced MR imaging (Figs. 7C and 7D).
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Serum levels of -fetoprotein were available in all 234 patients
before treatment. Of these patients, 95 patients (40.60%) had a normal serum
-fetoprotein level (< 20 mg/L), and 139 patients (59.40%) had an
elevated serum -fetoprotein level (range, 25–4300 mg/L). Within
2–4 weeks after treatment, the -fetoprotein level had decreased
in 92.81% (129/139) of the patients who had an elevated -fetoprotein
value before percutaneous microwave coagulation therapy, and the
-fetoprotein level had decreased to within the normal range (< 20
mg/L) in 72.66% (101/139) of these patients. The -fetoprotein level
significantly decreased in 20.14% (28/139) of these patients after microwave
therapy, although it did not drop to a normal level. The -fetoprotein
level remained unchanged after microwave treatment in 10 patients (7.19%).
Biopsies and Surgeries After Microwave Coagulation Therapy
Posttreatment biopsy was performed in 156 patients with 194 nodules within
1–3 months after percutaneous microwave coagulation therapy. Three to
five samples (mean, 3.7 specimens) from different parts of each tumor were
obtained. The results suggested that 180 (92.78%) of 194 nodules showed no
evidence of surviving tumor tissue, and these nodules had been replaced with
fibrotic tissue. Viable tumor cells were confirmed at biopsy in 14 patients.
Repeated treatment with microwave ablation was performed.
After finishing microwave therapy, six patients were willing to undergo removal of the coagulated lesions of the hepatocellular carcinoma. The lesions were resected completely at surgery. The pathology results revealed complete tumor necrosis in five patients, and 90% necrosis of tumor tissue in one patient.
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Causes of Death and Complications
Fifty-six patients had died by the end of this study. Twenty-six patients
died of advanced hepatocellular carcinoma; other causes of death were bleeding
in the upper gastrointestinal tract in 11 patients, liver failure in 13
patients, heart and kidney failure in five patients, and respiratory failure
in one patient. The perioperative mortality rate was 0% (calculated within 30
days of percutaneous microwave coagulation therapy).
No severe complications occurred in our study group. Local pain, varying from mild to severe, was experienced by most patients. Fever of 37.2–39.7°C developed on the day of percutaneous microwave coagulation therapy and continued for up to 3 days in 167 patients (71.37%). An increase in blood transaminase levels occurred in 65 patients after treatment and spontaneously dropped to a normal level within 1–2 weeks. Two patients whose nodules protruded beyond the liver capsule suffered skin burns. Eight patients had slight subcapsular bleeding observed on sonography. Minor pleural effusion developed in 11 patients whose nodules were located near the diaphragm. All of these side effects subsided with supportive treatment.
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For multiple electrode–insertion techniques, the distance between the electrodes is worth discussing. If the electrodes are placed too close together, wasteful overlapping coagulation may occur and the coagulated volume will not be enlarged adequately; if the electrodes are placed too far apart, incomplete coverage of the tumor may occur between the electrodes. The use of multiple electrodes maximized the volume of coagulated tissue; allowing the appropriate distance between the electrodes resulted in the simultaneous merging of several areas of coagulated tissue into one bigger volume of coagulated tissue, thus producing an integrated area in which no tumor tissue was untreated. The dynamic temperature monitors showed that at this optimized distance the temperatures at the center between two electrodes reached a high of more than 100°C within 100 sec of energy application. Therefore, from observing the temperature change, we speculated that the tissue between the electrodes might have been completely coagulated. As for the energy application, in our treatment sessions we activated the electrodes simultaneously, whenever possible, rather than separately as reported by some investigators [18]. This method increased the efficiency of thermal compensation between coagulation points and shortened the temperature curve, thus improving the coagulation effect. Our study showed that the survival rates for patients with tumors larger than 5 cm decreased with the increase of tumor size, but significant differences in survival rates were not shown between patients with tumors smaller than 3 cm and those with tumors that were 3–5 cm; this finding is counter to intuition and current clinical experience. This unexpected result may be because, through the appropriate use of simultaneous and multiple insertions in the center of the tumors, the coagulated areas were adequately enlarged and could envelope whole tumors smaller than 5 cm more effectively.
Another important factor affecting the therapeutic efficacy is the management of tissue blood perfusion. In a study by Rossi et al. [19] the volume of coagulated necrosis was limited because of the proximity of large vessels that acted as a heat sink during the radiofrequency thermal therapy. After occlusion of arterial blood flow to tumor, these researchers found that the area of coagulated necrosis was significantly enlarged. In our animal experiments and clinical trials, temperature measurements revealed that the maximum local temperature achieved was lower than that reached in simulation when the electrode was near large feeder blood vessels or areas with rich blood flow. In some cases, the temperature rose to an early plateau, but further increase in the temperature could be obtained only by increasing power output, not by extending the time. Another study showed that this phenomenon can be altered by applying high power output (75 W, 180–300 sec) to block the large blood vessels before performing liver tissue coagulation [14]. Therefore, this study revealed the importance of occluding large tumor feeder vessels before percutaneous microwave thermal ablation of hepatocellular carcinomas.
Many modalities, such as CT, MR imaging, sonography, and fine-needle aspiration biopsy, have been used to assess the efficacy of microwave coagulation therapy. Each has its advantages and disadvantages. CT was accepted as the standard and most reliable method of evaluating the extent of tumor necrosis induced by treatment because after the administration of a contrast agent the presence of vascular enhancement usually signified the persistence of viable tumors, and nonenhancement normally represented absence of viable tumor tissue. However, hepatic artery–related enhancement is sometimes observed in normal liver tissue adjacent to the necrotic region on follow-up CT, and such an abnormality might be misinterpreted as incomplete necrosis [20, 21]. Furthermore, in our experience, within 3 months after percutaneous microwave coagulation therapy, we found it difficult to differentiate viable tumor cells from reactive hyperthermia if enhancement of the area was seen at the periphery of the tumor on CT or MR imaging. Sonography may reveal a reduction in tumor size and show the changes in echogenicity in the treatment area, but these types of findings do not exclude the presence of viable tumor nests. Gadolinium-enhanced MR imaging is a more sensitive method than contrast-enhanced CT for evaluating the degree of tumor necrosis in most cases. In our experience, posttreatment biopsy with an 18-gauge needle has been a somewhat useful method when the imaging data fail to allow definitive judgment of whether necrosis is complete. To take advantage of each method, we used a combination of diagnostic tests to evaluate the treatment efficacy in our study.
The use of multiple-site dynamic temperature monitoring throughout the procedure allowed us to control the thermal field and attain necrosis while at the same time limiting the destructive effects on surrounding organs and liver tissue.
Recurrence of hepatocellular carcinoma after the initial treatment is frequent and is a major cause of poor outcome [22]. This phenomenon was also confirmed by the fact that 26 of the 56 deaths that occurred during our follow-up were associated with hepatocellular carcinoma recurrence in the liver. Many investigators have documented that tumor size, tumor cell differentiation, and the number of tumors were closely associated with rates of recurrence after percutaneous ethanol injection therapy [16, 23]. Our results also showed that patients with larger tumors shared a higher risk of local recurrence. Of the 16 local recurrences, eight occurred in nodules larger than 5 cm. However, for the overall recurrence rate, no statistical differences were found between tumors that were 3–5 cm and those that were smaller than 3 cm. This result is not in agreement with a previous report [16]. In fact, local recurrences are actually the residual tumors that were not adequately ablated during the initial treatment. With our improved percutaneous microwave coagulation therapy techniques, the appearance of complete necrosis could be observed in tumors smaller than 5 cm. Therefore, we had reason to expect a low local recurrence rate in tumors smaller than 5 cm.
Cumulative survival rates at 1, 2, 3, 4, and 5 years were 92.70%, 81.60%, 72.85%, 66.37%, and 56.70%, respectively. These results were encouraging compared with those associated with other current modalities. However, some limitations in this application exist. First, placement of the electrodes was technically challenging and sometimes time-consuming. Second, multiple percutaneous punctures are sometimes not feasible because of inadequate puncture routes. In our study, microwave coagulation was performed at laparotomy in five patients because of inadequate intercostal and subcostal space in the liver region. Third, in our experience, achieving satisfactory thermal control over tumors larger than 5 cm is difficult, although more insertions theoretically lead to larger coagulation volumes.
Given the fact that the survival rates of patients with hepatocellular carcinoma depend on many factors, such as underlying liver disease, treatment method, and tumor size and number [24], we cannot safely draw the conclusion that percutaneous microwave coagulation therapy is superior to other modalities. However, our study showed that percutaneous microwave coagulation therapy is a safe procedure; there were no perioperative deaths or severe complications. This method—multiple electrode insertion and simultaneous activation of the electrodes—offers the potential of largevolume coagulation necrosis for clinical ablation therapy.
In conclusion, local microwave coagulation therapy for hepatocellular carcinoma should be one of the nonsurgical modalities available to clinicians. Microwave interstitial thermal ablation is a safe and effective technique for the treatment of hepatocellular carcinoma. Iniial satisfactory clinical results showed that local microwave ablation for hepatocellular carcinoma with our microwave coagulation system can eliminate tumor in situ for nodules 5 cm or smaller in most cases and obtain good long-term results.
Acknowledgments
We are grateful to the National Scientific Foundation Committee of China
for its financial support for this project (30271252).
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2 cm; group 2, > 2–3 cm; group 3, > 3–5 cm; and
group 4, > 5 cm.
