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a Department of Surgery, St. George Hospital, Sydney, Australia
b Department of Radiology, St. George Hospital, Sydney, Australia
Accepted for publication November 10, 2008.
* Address correspondence to Prof Morris, Department of Surgery, St. George Hospital, Sydney, NSW, Australia (Email: david.morris{at}unsw.edu.au).
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Abstract |
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Methods: The clinical and treatment-related data regarding 129 consecutive percutaneous radiofrequency ablation treatment sessions for 100 patients with inoperable lung tumors were collected prospectively. Univariate and multivariate analyses were conducted to identify significant risk factors associated with postprocedural overall morbidity, pleuritic chest pain, hemoptysis, pneumothorax, pleural effusions, and chest drain requirement.
Results: There was no postprocedural mortality. The overall morbidity rate was 43% (n = 55 of 129). The most common adverse effect was pneumothorax, occurring in 32% (n = 41 of 129) of treatment sessions. Other significant complications included pleuritic chest pain (18%, n = 23 of 129), hemoptysis (7%, n = 9 of 129), pleural effusions (12%, n = 15 of 129), and chest drain insertion (20%, n = 26 of 129). Both univariate and multivariate analyses identified more than two lesions ablated per session as a significant risk factor for overall morbidity, pneumothorax, and chest drain insertion, but not for pleuritic pain, hemoptysis, and pleural effusions. Length of the ablation probe trajectory greater than 3 cm was an additional independent risk factor for overall morbidity and pneumothorax. Hilar location of lung tumor/s was the only independent risk factor associated with the increased incidence of hemoptysis.
Conclusions: Radiofrequency ablation for lung tumors can be considered as a safe and technically feasible procedure with acceptable incidence of complications.
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Introduction |
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Patients and Methods |
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TopAbstractIntroductionPatients and MethodsResultsCommentReferences |
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In this study, we were mainly interested in the feasibility of performing percutaneous RFA for primary and secondary lung tumors. Feasibility was defined as the ability to successfully perform a percutaneous RFA without significant morbidity or perioperative mortality. Significant morbidities included pleuritic pain requiring opioid analgesia, hemoptysis, pneumothorax, pleural effusions, and chest drain insertion.
Patient Selection
Selection of patients to undergo lung RFA was often multifactorial, and the consensus on the treatment plans for these patients was obtained from a group of surgical oncologists, medical oncologists, and a radiologist at weekly multidisciplinary seminars. Specific inclusion criteria consisted of (1) age between 18 and 85 years; (2) patients with early stage non–small cell lung carcinoma pulmonary metastases evaluated by thoracic surgeons at our institution and precluded from surgery because of poor pulmonary function with FEV1 (forced expiratory volume in 1 second) less than 1 L, cardiac risk with New York Heart Association Class of 3 or greater, or poor performance status with Eastern Cooperative Oncology Group performance of 2 or greater; and (3) patient refusing to undergo surgery.
Exclusion criteria included the following: (1) diameter of metastases greater than 5 cm; (2) greater than 6 lesions per hemithorax; (3) lesions immediately adjacent to major pulmonary vessels; (4) lesions located immediately adjacent to the pulmonary hilum of the lung; (5) lesions immediately adjacent to major bronchi; (6) bleeding diatheses not responding to medical treatment (prothrombin time greater than 1.5 and platelets less than 100 x 109); and (7) extrapulmonary disease.
Radiofrequency Ablation Technique
Before the procedure, all patients underwent clinical examinations, bone scans, and abdominal, pelvic, and chest computed tomography (CT) to assess the tumor and plan the procedure. Spirometry was a routine part of physiologic staging. Serial measurement of carcinoembryonic antigen was also obtained in patients with colorectal lung metastases. Positron emission tomography was used selectively at our institute.
Two interventional radiologists performed all the RFA procedures. Patient positioning for the 129 treatment sessions was determined by tumor location, with supine and prone positions to achieve the shortest probe trajectory to access anterior and posterior tumors, respectively. All the procedures were performed with the RITA star-burst XL electrode probe (RITA Medical, Mountain View, CA), which has a diameter of 14-gauge with nine deployable tines and is available in three lengths: 10, 15, and 25 cm. Only 10- and 15-cm probes were used owing to space limitations of the CT gantry. The electrode probe was able to create a maximal area of ablation of 5 cm. The generator used was the RITA 1500 generator (RITA Medical) with real-time recording as well as display of variables including temperature, power, and impedance.
Grounding pads were placed on both thighs with the wider edge facing the RFA site to lessen the risk of skin burns. All patients were provided with intravenous access. Both conscious sedation and general anesthesia have been used at our institute. The first 100 procedures were performed under conscious sedation consisting of generous local anesthesia (Lignocaine 1%, Pfizer Pty Ltd, Perth, Australia) and intravenous sedation (Morphine and Midazolam [Hospira Australia Pty Ltd, Melbourne, Australia] on demand). The subsequent 29 procedures were performed under general anesthesia and positive-pressure ventilation through endotracheal intubation.
All procedures were performed using aseptic technique, and the RFA probe was advanced to the tumor under CT (Xpress SX; Toshiba, Tokyo, Japan) fluoroscopic guidance. After confirming that the needle tip was advanced to the desired location in the tumor to be treated, an ablation algorithm with staged electrode deployment was used as per manufacturer instructions. A target temperature of 90°C and a maximum power of 150 W were used. The target temperature was maintained for 15, 20, and 27 minutes to achieve ablation zones of 3, 4, and 5 cm, respectively. Whenever technically feasible, an ablation margin of at least 1 cm in all planes was achieved. For ablations greater than 5 cm, overlapping ablations were performed to ensure complete ablation. Additional ablations were performed by withdrawing the electrode and changing its trajectory within the pulmonary parenchyma without rebreaching the pleura to reduce the incidence of pneumothorax. To prevent tumor seeding, track ablations were routinely performed to cauterize the access track on the way out at the completion of each tumor ablation. Throughout the procedure, the patients were continuously monitored for oxygen saturation, pulse rate, blood pressure, and temperature. This is continued hourly for 6 hours after the procedure. Preprocedural or intraprocedural antimicrobial agents were not routinely administered for prophylactic reasons.
Post-Radiofrequency Ablation Monitoring
All patients were monitored in hospital overnight, and chest radiography was performed after RFA procedure and before discharge to exclude pneumothorax and pleural effusions. Patients with small asymptomatic pneumothorax were observed. Symptomatic patients or those with large pneumothoraces or effusions were managed with chest drain insertion and repeat radiograph until the pneumothorax had resolved. After discharge, all patients were followed up with chest CT performed at 1 week, 1 month, and every 3 months thereafter to monitor the treatment response (see Fig 1
for sequential CT monitoring of an RFA-treated lesion).
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Relevant ablation variables consisted of number of overlapping ablations used per tumor, postablation size, total ablation time, patient positioning, type of anesthesia, and length of aerated lung traversed by the electrode probe. The length of the electrode trajectory through the aerated lung to each lesion was measured on CT images and defined as the distance from the site of pleural puncture to the edge of the tumor along the electrode trajectory. The postablation size was the diameter measured along the longest axis of the postablation zone. For patients who had multiple lesions ablated at a single session, the number of overlapping ablations and the postablation size of the largest lesion was used in the analysis. The longest electrode trajectory was recorded and used in the analysis if multiple electrode trajectories were created.
Statistical Analysis
Repeat ablation sessions were considered to be independent events, and analysis was performed by using the total number of ablation sessions as the sampling unit (total of 129 sessions). Multiple clinical and treatment-related variables were subsequently divided into categorical variables. The univariate analysis used to determine the underlying risk factors contributing to various complications was performed using the 
2 analysis or Fisher's exact test. Multivariate analysis using a binary logistic regression model was performed for various factors related to procedure-related complications to identify independent risk factors. A probability value less than 0.05 was considered to indicate significant difference for all analyses. Statistical analyses were all performed using a commercially available software program (SPSS for Windows, version 15.0, SPSS Inc, Chicago, IL).
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Results |
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Although postprocedural fever within 1 week of RFA procedure (body temperature > 38°C) was noted in 10% of cases (n = 13 of 129), pneumonia requiring antimicrobial treatment occurred only in 4% of cases (n = 5 of 129). There was one case of large hydropneumothorax, which was managed successfully with chest tube insertion for 7 days. Furthermore, we encountered 1 patient who experienced a 4- x 2-cm partial-thickness cutaneous burn at the site of the thigh grounding pad attachment. This required no debridement and healed completely in 2 months. Most patients were asymptomatic after treatment and were observed for 24 hours with serial chest radiographs before discharge from the hospital.
Risk Factors
Both univariate and multivariate analysis of 20 potentially significant factors was performed to determine risk factors for overall morbidity, pleuritic chest pain, hemoptysis, pneumothorax, pleural effusions, and chest drain insertion for the management of pneumothorax and pleural effusions. These factors consisted of (1) demographic factors including age (<65 years; n = 68 versus 
65 years; n = 61) and sex (male; n = 76 versus female; n = 53); (2) clinical factors including previous lung surgery (yes; n = 30 versus no; n = 99), pulmonary emphysema (yes; n = 16 versus no; n = 113), tumor diagnosis (colorectal metastases; n = 91 versus noncolorectal lesions; n = 32), number of pulmonary lesions treated (
2 lesions; n = 97 versus >2 lesions; n = 32), largest pulmonary lesion treated (2 cm; n = 80 versus >2 cm; n = 49), location of lesion (hilar; n = 28 versus peripheral; n = 101), proximity of lesion to bronchus (yes; n = 25 versus no; n = 107), proximity of lesion to pulmonary vessels (yes; n = 27 versus no; n = 107), distribution of lesions (bilateral; n = 33 versus unilateral; n = 96), and number of lobes treated (1 lobe; n = 76 versus >1 lobe; n = 53); and (3) treatment factors including size of ablation zone (3 cm; n = 42 versus >3 cm; n = 87), number of overlapping ablations (1; n = 105 versus >1; n = 24), total ablation time (<2 hour; n = 64 versus 2 hours; n = 65), length of probe trajectory (<3 cm; n = 78 versus 3 cm; n = 51), type of anesthesia (general anesthesia; n = 29 versus sedation; n = 100), patient position (supine; n = 65 versus prone; n = 64), repeat RFA (yes; n = 29 versus no; n = 100), and treatment period (first 3 years; n = 65 versus last 3 years; n = 64).
Overall Morbidity
Four risk factors significantly associated with overall morbidity were identified by univariate analysis, including greater than 2 lesions ablated (p 0.001), bilateral distribution of lesions (p = 0.024), total ablation time of 2 hours or greater (p = 0.033), and length of probe trajectory greater than 3 cm. Multivariate analysis further recognized number of lesions ablated (p < 0.001; odds ratio [OR], 15.812; 95% confidence interval [CI], 0.352 to 71.001) and length of probe trajectory (p = 0.030; OR, 2.895; 95% CI, 1.105 to 7.584) as two independent risk factors for increased frequency of overall morbidity.
Pain
Three factors significantly associated with pleuritic chest pain requiring opioid analgesia were identified by univariate analysis, including greater than 2 lesions ablated (p = 0.002), bilateral distribution of disease (p < 0.001), and total ablation time of 2 hours or greater (p = 0.020). Multivariate analysis suggested no independent risk factors for increased frequency of procedure related pleuritic chest pain.
Hemoptysis
One factor significantly associated with hemoptysis was identified by univariate analysis: hilar tumor location (p = 0.023). Multivariate analysis further recognized hilar location of tumor (p = 0.040; OR, 59.372; 95% CI, 1.214 to 129.82) as an independent risk factor for increased frequency of hemoptysis after RFA.
Pneumothorax
Five risk factors significantly associated with pneumothorax were identified on univariate analysis, including more than 2 lesions ablated (p 0.001), bilateral distribution of lesions (p = 0.009), more than 1 lobe ablated (p = 0.001), total ablation time of 2 hours or greater (p = 0.002), and length of probe trajectory greater than 3 cm (p = 0.033). Multivariate analysis further recognized number of lesions ablated (p < 0.001; OR, 31.614; 95% CI, 6.301 to 158.622) and length of probe trajectory (p = 0.042; OR, 3.108; 95% CI, 1.043 to 9.255) as two independent risk factors for increased frequency of pneumothorax.
Pleural Effusions
Four risk factors significantly associated with pleural effusions were identified on univariate analysis including more than 2 lesions ablated (p 0.001), bilateral distribution of lesions (p = 0.009), more than 1 lobe ablated (p = 0.011), total ablation time of 2 hours or greater (p = 0.025), and repeat RFA procedures (p = 0.022). Multivariate analysis suggested no independent risk factors for increased frequency of pleural effusions.
Chest Drain Placement
Two risk factors significantly associated with chest drain insertion were identified on univariate analysis, including more than 2 lesions ablated (p < 0.001), bilateral distribution of lesions (p = 0.007), and total ablation time of 2 hours or greater (p = 0.047). Multivariate analysis further recognized number of lesions ablated (p < 0.001; OR, 61.484; 95% CI, 7.038 to 197.12) as an independent risk factor for increased frequency of chest drain insertion.
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Comment |
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Pneumothorax was been consistently shown to be a very common complication [1–19]. The incidence of pneumothorax has been inconsistently reported, ranging from 4.5% to 61.1% [2–6, 8–15, 17–19]. These mixed results could be explained by the fact that the diagnostic definition of pneumothorax differs at different treatment centers [2–6, 8–15, 17–19]. Although some studies reported frequency of radiologically detected pneumothoraces irrespective of size, some centers only reported large or clinically significant pneumothoraces [2–6, 8–15, 17–19]. At our center, pneumothorax was the most common complication, occurring in 32% of RFA procedures. Our relatively high incidence could be attributable to our radiologic diagnosis (rather than clinical diagnosis) of pneumothorax on our routine postprocedural chest radiographs. Only 20 cases of pneumothorax (16%) required definitive chest drain insertion, and the duration of chest drain insertion was short, with an average drainage of 2 days.
The risk factors associated with pneumothorax in reported literature have also been conflicting [2, 15, 17–19]. Risk factors identified include (1) patient factors: male sex, no previous lung surgery, and presence of emphysema; (2) tumor factors: number of lesions ablated and lower and middle lobe involvement; and (3) protocol factors: RFA treatment period, length of aerated lung transversed by electrode, and number of ablation positions [2, 15, 17–19]. Our study also demonstrated the number of tumors greater than 2 and length of lung parenchyma traversed by probe trajectory greater than 3 cm as independent risk factors associated with increased incidence of pneumothorax. Number of tumors greater than 2 was a particularly significant risk factor for pneumothorax with an odds ratio of 31.614 when compared with tumor numbers ablated per session being less or equal to 2. This is only intuitive, as increased pleural punctures have been created, as would the risk of pneumothorax be greater. Furthermore, increased probe trajectory length may represent increased technical difficulty of reaching the tumor and increased need for repositioning of the ablation probe when compared with the more easily accessible tumors. We have altered our anesthetic regimen from conscious sedation to general anesthesia for better patient comfort and intraprocedural analgesic control. It is interesting to note at this point at our institution that general anesthesia with positive-pressure ventilation was not a risk factor for increased development of pneumothorax in both univariate and multivariate analysis.
Pleural effusions after ablation were also a common complication and occurred after 12% of treatment sessions. The pathogenesis of pleural effusions after RFA has been hypothesized to be initiated by the conductance of heat over the pleura during the tumor ablation. The majority of pleural effusions were small in amount and asymptomatic, with only six moderate to massive pleural effusions requiring chest tube drainage. Univariate analysis identified number of lesions ablated greater than 2, ablation of bilateral hemithoraces, number of lobes ablated greater than 1, and total ablation time greater than 2 hours as risk factors for the development of pleural effusions. This is understandable when such tumor- and treatment-related factors would all potentially predispose the pleura to longer exposure of heat irritation and hence the development of effusions.
Chest tube placement for pneumothorax and pleural effusions after RFA procedures occurred in 20% of procedures. This incidence of chest tube drainage is again inconsistent, ranging from 3.3% to 38.9% in different reported series [2–7, 10, 12, 14, 15, 17–19]. This inconsistency is largely explained by the differences in the management approach of RFA-related pneumothoraces [2–7, 10, 12, 14, 15, 17–19]. Some centers recommend treating pneumothoraces with aspiration only, whereas others, including our institution, prefer insertion of a chest tube with an underwater seal for drainage [2–7, 10, 12, 14, 15, 17–19]. Number of lesions ablated per session greater than 2 that increased the risk for both pneumothorax and pleural effusions was identified on multivariate analysis as the only significant risk factor for the higher prevalence of chest tube drainage.
In conclusion, our first 129 procedures for these 100 patients have demonstrated that RFA for unresectable lung tumors is technically feasible. The low complication rate, short chest tube insertion duration and hospital stay coupled with recently reported promising survival results suggest that this therapy may be a useful alternative for nonsurgical candidates. Increased understanding of the potential risk factors associated with common adverse events may facilitate better prevention and prompt recognition and management of complications.
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