Cardiovasc Intervent Radiol (2012) 35:860–867 DOI 10.1007/s00270-011-0221-z
CLINICAL INVESTIGATION
INTERVENTIONAL ONCOLOGY
Influence of Radiofrequency Ablation of Lung Cancer on Pulmonary Function Akihiro Tada • Takao Hiraki • Toshihiro Iguchi • Hideo Gobara • Hidefumi Mimura • Shinichi Toyooka • Katsuyuki Kiura • Toshihide Tsuda Toshiharu Mitsuhashi • Susumu Kanazawa
•
Received: 31 March 2011 / Accepted: 16 June 2011 / Published online: 2 July 2011 Ó Springer Science+Business Media, LLC and the Cardiovascular and Interventional Radiological Society of Europe (CIRSE) 2011
Abstract Purpose The purpose of this study was to evaluate altered pulmonary function retrospectively after RFA. Methods This retrospective study comprised 41 ablation sessions for 39 patients (22 men and 17 women; mean age, 64.8 years). Vital capacity (VC) and forced expiratory volume in 1 s (FEV1) at 1 and 3 months after RFA were compared with the baseline (i.e., values before RFA). To evaluate the factors that influenced impaired pulmonary function, univariate analysis was performed by using multiple variables. If two or more variables were indicated as statistically significant by univariate analysis, these
A. Tada (&) T. Hiraki H. Gobara H. Mimura S. Kanazawa Department of Radiology, Okayama University Medical School, 2-5-1 Kitaku Shikatacho, Okayama 700-8558, Japan e-mail:
[email protected]
variables were subjected to multivariate analysis to identify independent factors. Results The mean VC and FEV1 before RFA and 1 and 3 months after RFA were 3.04 and 2.24 l, 2.79 and 2.11 l, and 2.85 and 2.13 l, respectively. The values at 1 and 3 months were significantly lower than the baseline. Severe pleuritis after RFA was identified as the independent factor influencing impaired VC at 1 month (P = 0.003). For impaired FEV1 at 1 month, only severe pleuritis (P = 0.01) was statistically significant by univariate analysis. At 3 months, severe pleuritis (VC, P = 0.019; FEV1, P = 0.003) and an ablated parenchymal volume C20 cm3 (VC, P = 0.047; FEV1, P = 0.038) were independent factors for impaired VC and FEV1. Conclusions Pulmonary function decreased after RFA. RFA-induced severe pleuritis and ablation of a large volume of marginal parenchyma were associated with impaired pulmonary function.
S. Toyooka Department of Cancer and Thoracic Surgery, Okayama University Medical School, Okayama 700-8558, Japan
Keywords Radiofrequency ablation Pulmonary function Lung
K. Kiura Department of Respiratory Medicine, Okayama University Medical School, Okayama 700-8558, Japan
Introduction
T. Mitsuhashi Department of Epidemiology, Okayama University Medical School, Okayama 700-8558, Japan T. Iguchi Department of Radiology, Fukuyama City Hospital, Fukuyama 721-8511, Japan T. Tsuda Department of Environmental Epidemiology, Graduate School of Environmental Science, Okayama University Graduate School, Okayama 700-8530, Japan
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Radiofrequency ablation (RFA) is gaining popularity for the treatment of lung cancer, because it is technically simple and safe, providing good local control. Midterm survival after this treatment seems promising: 68% at 2 years [1], 75% at 2 years [2], and 74% at 3 years [3] for patients with clinical stage I non-small cell lung cancer; and 66% at 2 years [2] and 46–48% [4–6] at 3 years for patients with metastatic colorectal cancer. To minimize the risk of local tumor progression, ablation should be performed with adequate parenchymal margin. However,
A. Tada et al.: Pulmonary Function after RFA
ablation of marginal parenchyma might lead to pulmonary function loss. Furthermore, if severe pleuritis is induced by RFA, subsequently occurring pleural adhesion may impair pulmonary function. However, influence of RFA on pulmonary function has not been fully investigated. Therefore, the purpose of this study was to evaluate altered pulmonary function retrospectively after RFA. Furthermore, factors influencing impaired pulmonary function after RFA were investigated.
Methods and Materials Institutional review board approval of Okayama University Hospital (approval number: 90) and informed consent from patients were obtained for RFA of lung cancer. Our institutional review board gave us the approval and waived informed consent for this kind of retrospective study (approval number: 293).
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performed under local anesthesia alone (n = 20) or local plus epidural anesthesia (n = 21); general anesthesia was not used for RFA. After an anesthetic was introduced, the electrode was advanced into the tumor and connected to an RFA generator, and then, RF energy was applied. We used two types of electrodes: an internally cooled electrode (Cool-tip; Covidien, Mansfield, MA) for eight tumors, and a multi-tined expandable electrode (LeVeen; Boston Scientific, Natick, MA) for 43 tumors. The procedure was designed to treat the entire tumor and achieve an ablative margin of at least 0.5 cm around the tumors. After the procedure, chest CT images were obtained to assess the procedure. A chest radiograph was obtained 3 h later and the following morning to evaluate procedural complications. On the following morning, blood cell count and blood chemistry were examined. Thereafter, chest radiograph and blood examination were repeated whenever deemed necessary. Chest CT images were obtained 1 and 3 months after RFA to assess local efficacy.
Study Endpoints and Population Evaluation of Altered Pulmonary Function After RFA This study was retrospectively designed. Study endpoints included post-RFA altered pulmonary function and factors that influenced impaired pulmonary function after RFA. The inclusion criteria for this study were as follows: (1) chest CT and pulmonary function test with spirometry were performed within 1 week before RFA and 1 and 3 months after RFA; (2) no other therapy, such as systemic chemotherapy, radiation therapy, surgical treatment, or another RFA session was given within 3 months before and after RFA; and (3) no other pulmonary event (e.g., pneumonia, atelectasis, and pulmonary embolism) occurred within 3 months after RFA. This study focused on 39 patients (22 men and 17 women; mean age, 64.8 years; range, 35–78 years) who fulfilled the inclusion criteria between February 2007 and December 2009. A total of 51 lung tumors were treated during 41 RFA sessions. Thirty-one sessions (76%) involved a single tumor, and 10 sessions (24%) involved multiple tumors (mean number of tumors ablated per session 1.3; range 1–3). Ten patients had primary lung cancer, and 29 had secondary lung cancer, which was primarily from colorectal cancer (n = 14), primary lung cancer (n = 8), hepatocellular carcinoma (n = 3), renal cell carcinoma (n = 1), and others (n = 3). RFA Techniques The details of the procedure have been described previously [7]. Briefly, the procedure was performed percutaneously under CT fluoroscopic guidance (Asteion; Toshiba, Tokyo, Japan). All patients underwent chest CT immediately before RFA to target the tumor. REA was
Pulmonary function values used for evaluation were vital capacity (VC) and forced expiratory volume in 1 s (FEV1). The proportions of the pulmonary function values at 1 and 3 months after RFA to baseline values (i.e., before RFA) were calculated. Furthermore, the values at each time point were compared with those at other time points by using 1-factor repeated measures ANOVA. Evaluation of Factors Influencing Impaired Pulmonary Function After RFA We collected multiple variables, including age, gender, presence of pulmonary emphysema, occurrence of severe pleuritis after RFA, percentage of vital capacity to predicted value before RFA (pre-RFA %VC), percentage of FEV1 to forced vital capacity before RFA (pre-RFA FEV1%), distance to the nearest pleura from tumor, tumor type, tumor volume, ablated parenchymal volume, electrode type, and ablation time. When multiple tumors were treated during a session, the shorter or shortest distance to the nearest pleura from the tumors was considered; ablation time was the sum of RF energy applied for all treated tumors. Severe pleuritis was deemed to occur after RFA, when the following criteria were fulfilled: (1) pleural effusion was observed at the treated side on the chest radiograph obtained within 3 days of RFA; (2) C-reactive protein level was [10 mg/dl within 3 days of RFA; and (3) no other cause of inflammation. The tumor volume and ablation zone volume were calculated using the following formula: p/6 9 maximum
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862
diameter 9 diameter perpendicular to the maximum diameter 9 diameter in craniocaudal direction. Tumor diameters were measured on pre-procedural axial CT images. Ablation zone diameters were measured on axial CT images obtained immediately after RFA. The ablation zone was recognized as ground-glass opacity surrounding the tumors [8]. The maximum diameter and diameter perpendicular to the maximum diameter were measured on the image of maximal cross-section. The diameter in the craniocaudal direction was calculated by multiplying the number of slice images in which the tumor and ablation zone were demonstrated by slice thickness. The ablated parenchymal volume was calculated by subtracting the tumor volume from the ablation zone volume. According to the category or value of each variable, the 41 sessions were categorized into 2 groups. Age was categorized using mean value as a threshold. Tumor volume, ablated parenchymal volume, and ablation time was categorized by using median value as a threshold. First, the proportions of pulmonary function values at 1 and 3 months after RFA to baseline values were compared between the two groups by univariate analysis by using the Student’s t test. Subsequently, if two or more variables were found to be significantly different by the analyses, multiple linear regression analysis was performed by using such variables to determine an independent factor. All analyses were performed using the Statistical Package for the Social Sciences (SPSS) software (version 11.0; SPSS Inc, Chicago, IL). For all analyses, P \ 0.05 was considered statistically significant.
A. Tada et al.: Pulmonary Function after RFA
respectively (Fig. 1B); thus, the mean [±SD] 1- and 3-month-to-baseline FEV1 proportions were 94.5% [±11] (range 64.5–125%) and 94.7% [±8.9] (range 73.8–122.8%), respectively. The VC and FEV1 values at 1 month were significantly lower (P = 0.001 each for VC
Results The mean tumor volume was 2.7 (range 0.1–16.8) cm3, whereas the mean ablation zone volume was 27.9 (range 6.0–99.9) cm3; thus, the mean ablated parenchymal volume was 25.2 (range 5.8–93.7) cm3. All 51 ablated tumors were considered to be completely involved in the ablation zone on CT images obtained immediately after RFA. None of the tumors showed local progression until 3 months of RFA. Altered Pulmonary Function After RFA The mean [± standard deviation (SD)] VC value before and after 1 and 3 months of RFA were 3.04 l [±0.75], 2.79 l [±0.55], and 2.85 l [±0.51], respectively (Fig. 1A); thus, the mean [±SD] 1- and 3-month-to-baseline proportions of VC were 92.6% [±14.4] (range 56.3–150%) and 94.6% [±11.6] (range 70.3–143.2%), respectively. Similarly, the mean [±SD] FEV1 before and after 1 and 3 months of RFA were 2.24 l [±0.65], 2.11 l [±0.4], and 2.13 l [±0.43],
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Fig. 1 Time-series graphs showing VC (A) and FEV1 (B) before and after 1 and 3 months of RFA. A Mean VC values before and after 1 and 3 months of RFA were 3.04 l (range 1.57–4.51 l), 2.79 l (range 1.56–4.49 l), and 2.85 l (range 1.57–4.6 l), respectively. The VC values at 1 and 3 months were significantly lower (P = 0.001 and P = 0.002, respectively) than baseline values. The VC values at 3 months were not significantly different (P = 0.12) from those at 1 month. B The mean FEV1 values before and after 1 and 3 months of RFA were 2.24 l (range 0.85–3.49 l), 2.11 l (range 0.83–3.41 l), and 2.13 l (range 0.79–3.39 l), respectively. The FEV1 values at 1 and 3 months were significantly lower (P = 0.001 each) than baseline values. The FEV1 values at 3 months were not significantly different (P = 1) from those at 1 month
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Table 1 Two cases that required home oxygen therapy after radiofrequency ablation Case
Vital capacity (l) Baseline
Forced expiratory volume in 1 s (l)
1 month
3 months
Baseline
1 month
3 months
Emphysema
Severe pleuritis
Ablated parenchymal volume (cm3)
2
2.53
2.1 (83)
2.09 (83)
1.42
1.41 (99)
1.26 (89)
Yes
No
42.9
6
3.4
2.4 (71)
2.62 (77)
2.83
2.62 (84)
2.74 (86)
Yes
Yes
24.2
The value in parenthesis is percentage of baseline
and FEV1) than baseline values. The VC and FEV1 values at 3 months also were significantly lower (P = 0.002 for VC and P = 0.001 for FEV1) than baseline values. The VC and FEV1 values at 3 months were not significantly different (P = 0.12 for VC and P = 1 for FEV1) from those at 1 month. Any respiratory symptom did not develop after RFA in 37 patients, whereas two patients required home oxygen therapy after RFA. The data on the two cases are shown in Table 1.
The mean [±SD] 1-month-to-baseline FEV1 proportion for patients with severe pleuritis after RFA was 87.8% [±12.2] (range 72.2–117.7%). The mean [±SD] 3-month-to-baseline FEV1 proportion for patients with severe pleuritis after RFA was 88.3% [±8.6] (range 73.9–106.2%). The mean [±SD] 3-month-to-baseline FEV1 proportion for patients with an ablated parenchymal volume C20 cm3 was 91.4% [±8.4] (range 73.8–105.3%).
Factors That Influencing Impaired Pulmonary Function after RFA
Discussion
The results from the Student’s t tests used to evaluate factors that influence impaired VC revealed that male gender (P = 0.03), pre-RFA FEV1% \70% (P = 0.04), occurrence of severe pleuritis (P \ 0.001), and tumor volume C1.3 cm3 (P = 0.04) significantly impaired VC at 1 month. At 3 months, male gender (P = 0.046), occurrence of severe pleuritis (P = 0.01), tumor volume C1.3 cm3 (P = 0.02), and ablated parenchymal volume C20 cm3 (P = 0.009) significantly impaired VC (Table 2). Multiple linear regression analysis identified severe pleuritis (P = 0.003), severe pleuritis (P = 0.019), and ablated parenchymal volume C20 cm3 (P = 0.047) to be independent factors at 1 and 3 months, respectively (Table 3). The mean [±SD] 1-month-to-baseline proportion of VC for patients with severe pleuritis after RFA was 81% [±8.7] (range 70.6–100.4%). The mean [±SD] 3-month-to-baseline proportion of VC for patients with severe pleuritis after RFA was 87.5% [±8.8] (range 76.8–104.9%). The mean [±SD] 3-month-to-baseline proportion of VC for patients with an ablated parenchymal volume C20 cm3 was 90.3% [±8.9] (range 70.3–104.6%). The Student’s t test showed that only the occurrence of severe pleuritis was significant (P = 0.01) at 1 month and that the occurrence of severe pleuritis (P = 0.002), tumor volume C1.3 cm3 (P = 0.02), and ablated parenchymal volume C20 cm3 (P = 0.01) significantly impaired FEV1 at 3 months (Table 2). Multiple linear regression analysis showed that both occurrence of severe pleuritis (P = 0.003) and ablated parenchymal volume C20 cm3 (P = 0.038) were significant independent factors at 3 months (Table 4).
Few studies have evaluated the influence of RFA on pulmonary function. Ambrogi et al. [9] had findings similar to our findings, where pulmonary function decreased 1 month after RFA, although not statistically significant, and then recovered to some extent at 3 months. The mean forced VC was 2.63 and 2.80 l at 1 and 3 months, respectively, compared with 2.91 l before RFA; the mean FEV1 was 1.71 and 1.86 l at 1 and 3 months, respectively, compared with 1.97 l before RFA. The multicenter prospective study by Lencioni et al. [2] also showed impaired pulmonary function after RFA in 22 patients with non-small cell lung cancer with mean forced VC and FEV1 of 2.6 and 1.7 l, respectively, at 1 month, compared with 2.9 and 1.9 l, respectively, before RFA, although the differences were not statistically significant. In contrast, de Bae`re et al. [10] reported that pulmonary function did not decrease after RFA; the mean VC and FEV1 were 2.9 and 2.2 l, respectively, after RFA, compared with 2.9 and 2.2 l, respectively, before RFA. Although our results were similar to the results of previous two studies by Ambrogi et al. and Lencioni et al., those were different from the results of the study by de Bae`re et al. Although the exact reason for the difference cannot be determined, we speculate that our study included relatively high rate (34%, 14/41) of the patients with pulmonary emphysema that were related to severe pleuritis after RFA and larger ablated parenchymal volume (see Appendix). Factors that affect pulmonary function by RFA are poorly understood. The results obtained in this study seem to verify our hypothesis that induced severe pleuritis and ablated parenchymal volume are associated with impaired
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A. Tada et al.: Pulmonary Function after RFA
Table 2 Results of univariate analyses to determine factors for vital capacity and forced expiratory volume in 1 s after radiofrequency ablation Vital capacity Variable
1 month/ baseline (%) (mean ± SD)
Age (year)
Forced expiratory volume in 1 s P value
3 months/ baseline (%) (mean ± SD)
0.99
P value
1 month/ baseline (%) (mean ± SD)
0.92
P value
3 months/ baseline (%) (mean ± SD)
0.83
0.81
\65 (n = 17)
92.6 ± 9.8
94.4 ± 8.5
94.1 ± 4.6
95.1 ± 6.4
C65 (n = 24)
92.6 ± 17.1
94.7 ± 13.6
94.8 ± 14
94.4 ± 10.5
Gender
0.03
Male (n = 23)
88.4 ± 12.1
Female (n = 18)
98 ± 15.5
Emphysema
0.046 91.4 ± 8.8 98.7 ± 13.7
0.08
Yes (n = 11)
86.2 ± 9
No (n = 30)
95.0 ± 15.3
Pre-RFA %VC (%)
90.2 ± 8.5
100.8 ± 28.6
C80 (n = 36) \70 (n = 14) C70 (n = 27)
86.2 ± 9.6 96.0 ± 15.4
90.3 ± 9.1 96.8 ± 12.3
Yes (n = 12)
81 ± 8.7
No (n = 29)
97.4 ± 13.6
Type of tumor
0.01
0.07 91.2 ± 8.7 96.5 ± 8.6
0.01 87.8 ± 12.2
97.6 ± 11.5 0.33
94.5 ± 7.4 0.8
93.8 ± 13.9 94.9 ± 9.4
87.5 ± 8.8
0.88 95.8 ± 17.8
93.9 ± 9.8 0.09
\0.001
Severe pleuritis
96.1 ± 8.4 0.34
98.8 ± 18.7
93.7 ± 8.9 0.04
0.1 90.9 ± 9.6
94.8 ± 10.1 0.51
101.5 ± 24.2
91.5 ± 11.5
Pre-RFA FEV1 (%)
97.4 ± 8.5 0.77
93.6 ± 13.7
96.2 ± 12.3
0.09 92.6 ± 8.8
96.3 ± 9.4 0.15
0.51
\80 (n = 5)
0.36 93.1 ± 12.1
0.002 88.3 ± 8.6
97.3 ± 9.3 0.41
97.3 ± 7.8 0.59
0.2
Primary (n = 11)
88.7 ± 11.6
91.9 ± 8.2
92.9 ± 10.1
91.6 ± 9
Metastasis (n = 31)
93.9 ± 15.1
95.5 ± 12.5
95.1 ± 11.4
95.7 ± 8.8
Minimum distance to pleura of ablated tumors (mm)
0.12
0.07
0.33
\5 (n = 17)
88.8 ± 11.2
90.7 ± 7.8
92.5 ± 11.3
C5 (n = 24)
95.5 ± 15.8
97.4 ± 13.1
95.9 ± 10.8
Tumor volume (cm3) \1.3 (n = 22)
0.04
C1.3 (n = 19)
0.02
0.1 92.0 ± 7.9 96.6 ± 9.2
0.31
0.02
96.8 ± 15.3
98.4 ± 12.7
96.2 ± 10
98.4 ± 9.1
87.8 ± 11.8
90.2 ± 8.6
92.6 ± 12.1
91.2 ± 7.4
3
Ablated parenchymal volume (cm )
0.09
\20 (n = 19)
96.7 ± 15.9
C20 (n = 22)
89.0 ± 12.1
Electrode
0.009 99.6 ± 12.1
Multitined expandable (n = 35)
92.7 ± 15.1
Single internally cooled (n = 6)
92.3 ± 10.1
Ablation time (min)
0.81 95 ± 10.3
90.3 ± 8.9 0.96 94.9 ± 12.4
91.4 ± 8.4 0.47
95 ± 11.3
93.1 ± 6.2 0.82
0.01 98.5 ± 8.1
94.1 ± 11.8 0.74
0.42 95.2 ± 9.1
91.5 ± 9.4 0.39
P value
91.9 ± 7.7 0.24
0.73
\27 (n = 20)
93.2 ± 8.8
96.2 ± 6.7
92.4 ± 7.6
95.2 ± 7.6
C27 (n = 21)
92.1 ± 18.4
93.1 ± 15
96.5 ± 13.4
94.2 ± 10.2
SD standard deviation; Pre-RFA %VC percentage of vital capacity to predicted value before radiofrequency ablation; pre-RFA FEV1% forced expiratory volume in 1 s to forced vital capacity before radiofrequency ablation
pulmonary function by RFA. We assume that pain and pleural adhesion resulting from severe pleuritis might be related to impaired pulmonary function. Specifically, at 1 month, inflammation due to pleuritis persisted to a degree, and thus, occurrence of severe pleuritis was the most
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important factor at 1 month. At 3 months, a larger ablated parenchymal volume was another important factor. Ablation followed by coagulation of the parenchyma may lead to functional loss. Furthermore, additional functional loss might occur during the healing process of the ablation zone.
A. Tada et al.: Pulmonary Function after RFA
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Table 3 Results of multiple linear regression analysis of vital capacity 1 month and 3 months after radiofrequency ablation 1 month Variable
Coefficient (b)
Intercept
103.24
Gender (male) Pre-RFA FEV1% \70% Severe pleuritis (?) Tumor volume C1.3 cm3
3 months 95% CI
P value
-5.72
-13.87 to 2.44
0.16
-2.61
-11.41 to 6.19
0.55
-13.71
-22.5 to -4.92 -13.22 to 2.4
-5.41
Coefficient (b)
95% CI
P value
-4.28
-10.74 to 2.19
0.19
0.003
-8.4
-15.32 to -1.48
0.019
0.17
-3.52
-10.37 to 3.34
0.31
-6.79
-13.5 to -0.81
0.047
104.74
Ablated parenchymal volume C20 cm3
Pre-RFA FEV1% forced expiratory volume in 1 s to forced vital capacity before radiofrequency ablation
Table 4 Results of multiple linear regression analysis of forced expiratory volume in 1 s, 3 months after radiofrequency ablation
Variable
Coefficient (b)
Intercept
101.49
Severe pleuritis (?) Tumor volume C1.3 cm3 Ablated parenchymal volume C20 cm3
This is because shrinkage of the ablation zone may retract the surrounding nonablated parenchyma, resulting in a decrease in alveoli compliance. According to reports on pulmonary function after surgical resection, FEV1 at 1 and 3 months after lobectomy was 79.5 and 84% of the baseline value, respectively, and FEV1 at 1 and 3 months after pneumonectomy was 65 and 66% of baseline, respectively [11]. Forced VC and FEV1 at 2 months after segmentectomy were 89.6 and 90.5% of baseline, respectively, and those at 2 months after lobectomy were 84 and 83.2% of baseline, respectively [12]. Comparing this data with our results, RFA seems to affect pulmonary function less than the pulmonary surgeries. Nevertheless, this study suggests that pulmonary function may decrease by up to 30% if the patients suffer from severe pleuritis or the ablated parenchymal volume is C20 cm3. Although decrease of pulmonary function is clinically insignificant in the majority of cases, two patients required home oxygen therapy after RFA. Thus, application of RFA should be carefully determined for patients with severely impaired pulmonary function. There were several limitations of this study. It was based on data from only a subsection of patients who underwent RFA for lung cancer because of relatively strict inclusion criteria. The study population was heterogeneous in terms of cancer type and type of electrode used. The ablation zone volume measured by us was not necessarily precise. For example, ground-glass opacity induced by thermal damage immediately after RFA may not be clear enough to recognize, which may lead to an underestimation of the ablation zone volume. In contrast, the associated parenchymal
95% CI
P value
-8.04
-13.16 to -2.91
0.003
-3.45
-8.48 to 1.58
0.17
-5.3
-10.28 to -0.32
0.038
hemorrhage, congestion, and edema, all of which may result in ground-glass opacity, may lead to an overestimation. However, such measurement errors were assumed to be too small to influence substantially the statistical outcomes. Evaluation of pulmonary function was limited to a 3-month period after RFA. However, it would be more difficult to evaluate the influence of RFA on pulmonary function at a later phase, because various other influencing factors, including additional treatment for lung cancer, cancer progression, and aging-associated regressive changes, may also be related to impaired pulmonary function. In conclusion, pulmonary function significantly decreased 1 and 3 months after RFA. The mean proportion of VC and FEV1 was 92.6 and 94.5% at 1 month, and 94.6 and 94.7% at 3 months, respectively, compared to baseline. The occurrence of severe pleuritis after RFA was significantly associated with impaired pulmonary function at 1 month. At 3 months, a larger ablated parenchymal volume was another significant factor. Conflict of Interest
None.
Appendix Severe pleuritis and larger ablated parenchymal volume were the variables that were obtained after RFA. Thus, regrettably, those were not quite helpful in predicting impaired pulmonary function in advance. Then, additional analysis was performed to evaluate the predictive factors for the occurrence of severe pleuritis and larger ablated
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866 Table 5 Results of univariate analyses of predictive factors for severe pleuritis and ablated parenchymal volume
A. Tada et al.: Pulmonary Function after RFA
Severe pleuritis Variable
No (n = 29)
Yes (n = 12)
Age (year)
\20 cm3 (n = 19)
C20 cm3 (n = 22)
12
5
7
10
C65
17
7
12
12
Female
14
4
10
8
Male
15
8
9
14
0.5
0.3
0.052
0.029
5
6
2
9
24
6
17
13
\80
4
1
2
3
C80
25
11
17
19
\70
7
7
6
8
C70
22
5
13
14
5
5
14
17
No Pre-RFA %VC (%)
1
Pre-RFA FEV1 (%)
Primary Metastasis
6
4
23
8
10
7
C5
19
5
Tumor volume (cm3)
0.07 5
12
14
10
14
8
5
14
0.32
\1.3
17
5
C1.3
12
7
Electrode
parenchymal volume. Univariate analysis with chi-square test or Fisher’s exact tests was performed by using multiple variables that were available before RFA, including age, sex, pulmonary emphysema, pre-RFA %VC, pre-RFA FEV1%, tumor type, distance to the nearest pleura from tumors, tumor volume, and electrode type. The results are shown in Table 5. Although there was no variable significantly increasing a risk of severe pleuritis, pulmonary emphysema had a tendency (P = 0.052) to be associated with the occurrence of severe pleuritis after RFA. The variables that increased a risk of larger ablated parenchymal volume significantly were emphysema (P = 0.029) and tumor volume C1.3 cm3 (P = 0.011). Given that ventilation and perfusion has heat sink effect, decreased ventilation and perfusion in the emphysematous lung may explain the association between pulmonary emphysema and more extensive ablation leading to severe pleuritis and larger ablated parenchymal volume.
1
0.18
\5
Multitined expandable
0.75
0.44
Minimum distance to pleura of ablated tumors (mm)
Single internally cooled
1
0.68
Tumor type
P value 0.58
\65
Emphysema Yes
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P value 1
Gender
Pre-RFA %VC percentage of vital capacity to predicted value before radiofrequency ablation; Pre-RFA FEV1% forced expiratory volume in 1 s to forced vital capacity before radiofrequency ablation
Ablated parenchymal volume
0.011
0.33
1
3
3
3
3
26
9
16
19
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A. Tada et al.: Pulmonary Function after RFA
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