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Ann Thorac Surg 2006;82:1828-1834
© 2006 The Society of Thoracic Surgeons
a Thoracic Surgery Division, Emphysema Center, Policlinico Tor Vergata University, Rome, Italy
b Department of Radiology, Emphysema Center, Policlinico Tor Vergata University, Rome, Italy
Accepted for publication May 15, 2006.
* Address correspondence to Prof T. Mineo, Cattedra di Chirurgia Toracica, Policlinico Tor Vergata, Viale Oxford 81, I-00133 Rome, Italy (Email: mineo{at}med.uniroma2.it).
Presented at the Poster Session of the Forty-second Annual Meeting of The Society of Thoracic Surgeons, Chicago, IL, Jan 30–Feb 1, 2006.
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Abstract |
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 Top Abstract IntroductionPatients and MethodsResultsCommentAcknowledgmentsReferences |
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METHODS: The study enrolled 39 patients (mean age, 67 ± 2.1 years). All patients underwent preoperative and postoperative pulmonary function tests. Cut-off values for postoperative forced expiratory volume in 1 second (FEV1) were 65% of the predicted value for pneumonectomy and 45% for lobectomy. A semiquantitative analysis of planar and SPECT lung perfusion scintigraphy images was performed preoperatively to estimate postoperative predicted FEV1 (FEV1ppo). Relationships between FEV1ppo and measured postoperative FEV1 were tested by the Pearson correlation and Bland Altman agreement tests.
RESULTS: Twenty-eight lobectomies and 11 pneumonectomies were performed. The FEV1ppo estimated by mean planar lung scintigraphy was 1.85 ± 0.38 L, with a Pearson correlation coefficient to the measured FEV1 of 0.8632 (p < 0.001). The mean FEV1ppo estimated by SPECT was 1.78 ± 0.31 L, with a Pearson coefficient to the measured FEV1 of 0.8527 (p < 0.001). Both values showed a more significant correlation with postoperative measured FEV1 after lobectomy (p < 0.001) than after pneumonectomy (p = 0.045). The Bland Altman test confirmed satisfactory agreement of FEV1ppo estimated by both planar lung scintigraphy and SPECT with FEV1 measured by spirometry.
CONCLUSIONS: Both planar lung scintigraphy and SPECT can accurately predict postoperative FEV1 and can therefore be considered reliable tools in establishing operability of patients with lung cancer and ventilatory obstruction.
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Introduction |
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TopAbstractIntroductionPatients and MethodsResultsCommentAcknowledgmentsReferences |
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A forced expiratory volume in 1 second (FEV1) > 2 L or > 60% of the predicted value usually accounts for a feasible pneumonectomy, with the values lowered to > 1.5 L or > 40% of the predicted value for a lobectomy [4, 5], thus excluding a considerable number of subjects who have a resectable disease but whose pulmonary function appears too compromised for them to successfully undergo lung resection.
Spirometry-based pulmonary function tests have become the gold standard of preoperative functional assessment of lung function, but the constant need for more accurate evaluation tools led to the use of perfusion or ventilation lung scintigraphy, or both, to provide a regional assessment of lung function and thus offer the possibility of estimating postoperative pulmonary function by means of the predicted postoperative FEV1 (FEV1ppo). In particular, a FEV1ppo of 0.8 to 1.0 L or exceeding 40% of the predicted value is currently accepted as the cutoff for pneumonectomy [6, 7], although reliability and usefulness of these are still under scrutiny [8–10].
The aim of this study was to compare the role and usefulness of preoperative planar acquisition lung perfusion scintigraphy (PALPS) versus single-photon emission computed tomography (SPECT) in patients with ventilatory obstruction undergoing surgery for lung cancer.
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Patients and Methods |
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TopAbstractIntroductionPatients and MethodsResultsCommentAcknowledgmentsReferences |
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Preoperative and postoperative (60 ± 22 days) pulmonary function tests were performed according to the American Thoracic Society guidelines [4]. The preoperative evaluation included a total body CT scan, fiberoptic bronchoscopy, and videomediastinoscopy when appropriate. For the purpose of this study, PALPS and SPECT were also performed with semiquantitative analyses of planar and CT images.
Cutoff values of 65% of the predicted FEV1% for pneumonectomy and 45% for lobectomy were established for inclusion in the surgical protocol. Since an increase of 5% in both these values has been assumed to be a "safety threshold" on postoperative outcome [2, 3, 11, 12], we maintained the same criteria. Twenty-eight lobectomies and 11 pneumonectomies were performed.
Lung Perfusion Scintigraphy
A dual-head, variable-angle gamma camera (Millenium VG; General Electric Medical Systems, Milwaukee, WI) with high-resolution low-energy collimators was used to perform lung perfusion scintigraphy. Five minutes after intravenous administration of technetium Tc 99m macroaggregated albumin (about 185 MBq), planar images of the lungs were acquired in the anterior, posterior, lateral, and oblique posterior projections (1 million counts each). Once PALPS was completed (Fig 1A), a SPECT acquisition over 36 nm (matrix 12.8 x 12.8, 0.3 nm angle steps, 25 seconds/frame) was performed (Fig 1B).
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Statistical Analysis
FEV1ppo values were compared with the postoperative FEV1 values. The Pearson correlation test was used to investigate the relationship between postoperative predicted and measured FEV1 values. The Bland Altman test [15] was used to test agreement between scintigraphy-estimated and spirometry-measured data.
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Results |
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TopAbstractIntroductionPatients and MethodsResultsCommentAcknowledgmentsReferences |
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When the type of surgical procedure was considered, FEV1ppo values estimated by PALPS and SPECT both showed a stronger correlation with measured postoperative FEV1 after lobectomy than after pneumonectomy, even though SPECT seemed to be more accurately predictive in the latter (Table 2). When agreement between PALPS estimated FEV1 values and those measured by pulmonary function tests were examined, the Bland Altman test showed a difference of the means of 0.1303 L, with 97.4% of the values within the mean ± 2SD for absolute FEV1 values and of 3.304% with 92.3% of values within the mean ± 2SD for the percent predicted values. In a similar manner, SPECT showed a satisfactory agreement with spirometry-measured FEV1 in absolute values (difference between the means, 0.0528 L with 92.3% of values within the mean ± 2SD) and in percent predicted (difference between the means, 1.177% with 92.3% of values within the mean ± 2SD) (Figs 2 and 3).
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Comment |
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TopAbstractIntroductionPatients and MethodsResultsCommentAcknowledgmentsReferences |
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Safety threshold values for FEV1 are currently set at > 2 L for a pneumonectomy and > 1.5 L for a lobectomy. The percent predicted FEV1 appears a more useful index because it accounts for gender and size variability of patients being evaluated for lung resection. A predicted FEV1 > 80% therefore makes a patient suitable for pneumonectomy without need for further evaluation [3, 16, 17].
Several studies have confirmed the value of the FEV1ppo in predicting postoperative morbidity and mortality after lung resection [2, 4, 6, 10, 12, 18]. Even this index has, nonetheless, never been universally accepted, gradually shifting clinicians' interest to methods able to effectively estimate postoperative residual lung function. This because postsurgical functional loss varies with the amount of resected lung, the relative function of the removed tissue being compared with the remaining one, and the baseline functional impairment.
Split function studies such as quantitative lung perfusion scintigraphy have made it possible to calculate the function of the excised tissue in relation to overall pulmonary function, therefore predicting postoperative residual function [7]. Lung perfusion scintigraphy with Tc-labeled macroaggregates of albumin is the currently recommended protocol to estimate the FEV1ppo. Alternative, cheaper techniques such as segment counting have been proposed by Zeiher and colleagues [19]. The major drawback of this technique is that it assumes that each segment of both lungs contributes equally to lung function, an assumption that does not fit most patients with COPD. In addition, gross underestimation of postoperative FEV1 may be determined by centrally located cancer masses causing uneven lung perfusion [9, 20]. Therefore, even though the American College of Chest physicians and the British Thoracic Society do not currently recommend using scintigraphy for preoperative assessment of lung cancer patients undergoing lobectomy, this technique has become a standard test in the preoperative evaluation of patients scheduled for pneumonectomy.
PALPS is a simple technique that proved effective in predicting postoperative outcome of patients with severe COPD [21]. We hypothesize that surgical candidates with preoperative FEV1 < 60% should always undergo lung perfusion scintigraphy to achieve accurate postoperative outcome prediction with an estimated FEV1ppo > 40% indicating an acceptable surgical risk.
Preoperative assessment by means of perfusion SPECT imaging is still being evaluated. Postoperative FEV1 estimation by perfusion SPECT demonstrates good correlation with spirometrically measured FEV1. In addition, SPECT estimation of FEV1ppo proved more accurate than planar scintigraphy estimated values [21], leading Hirose and colleagues [22] and Wu and colleagues [23] to consider SPECT images as more useful than planar images to assess resectability [22, 23]. In our study, FEV1ppo, estimated by planar scintigraphy or SPECT acquisition, was similar compared with spirometry-measured postoperative FEV1.
These results are comparable with those reported in a previous study by Piai and colleagues [14] in which no significant difference was observed between the two techniques, although in this latter study, integration of SPECT images with CT was suggested to provide more precise anatomic information. Wu and colleagues [23] also considered quantitative CT scanning to be an adequate tool because it is now routinely performed during the preoperative work-up for lung cancer surgery, it is semiautomated and can be performed by a trained technician, and it is not complicated or time-consuming.
The same authors [23], however, admit that patients undergoing lobectomy with a quantitative CT-predicted FEV1ppo of about 40% or less should also receive a perfusion scintigraphy. Such technique has effectively been extensively used to predict lung function after resection and is still the simplest and most reliable method, even if it can underestimate postoperative measured FEV1 values. Conversely, CT-based methods require more postprocessing and are limited by the need for scanner calibration, the dependence of lung density on the inspiratory effort, and the x-ray beam collimation [20].
In our opinion, FEV1ppo estimated by both planar lung scintigraphy and SPECT correlates well with spirometry-measured postoperative FEV1, and therefore appears to be a good marker of surgical feasibility in patients with ventilatory obstruction. Although results achieved by planar lung scintigraphy and SPECT were comparable in this study, we have found that SPECT accounts better for spatial overlapping of the pulmonary lobes and differences in their size or perfusion and better estimates hypoperfused areas/segments in candidates for lobectomy or pneumonectomy with no additional cost. Our overall results seems to confirm the usefulness of combining CT-provided anatomic information with physiologic information obtained by scintigraphy-based image fusion algorithms [17, 21, 24].
In conclusion, PALPS and SPECT both helped predict postoperative pulmonary function in patients in this study with significant ventilatory defect undergoing anatomic lung resection. Eventual confirmation of our findings by larger studies will probably contribute to further increase the number of patients with resectable lung cancer and impaired pulmonary function who might benefit from curative lung resection with acceptable risks of mortality and morbidity.
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Acknowledgments |
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TopAbstractIntroductionPatients and MethodsResultsCommentAcknowledgmentsReferences |
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References |
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