Preoperative evaluation of the lung resection candidate

For patients with localized lung cancer, lung resection provides the highest likelihood of a cure. However, only about 20% to 30% of patients are potential candidates for surgical resection because of the stage at which the disease is diagnosed or because of comorbid conditions.^1,2 In one study, poor lung function alone ruled out more than 37% of patients who presented with anatomically resectable disease.³ The poor prognosis for patients who do not undergo surgery, the likelihood of early mortality from lung resection, and the potential for loss of lung function following resection are all important considerations in the preoperative pulmonary evaluation of candidates for anatomical lung resection.

PROGNOSIS OF LUNG CANCER POOR WITHOUT SURGICAL RESECTION

Several studies support the poor prognosis of lung cancer patients who do not undergo resection. In one study of 1,297 screen- and symptom-detected patients, the median duration of survival without surgery was 25 months for patients with screen-detected stage I lung cancer (n = 42) and 13 months for those with symptom-detected stage I disease (n = 27).⁴ Another study of 799 patients with stage I lung cancer who were not treated surgically reported 5- and 10-year survival rates of 16.6% (n = 49) and 7.4% (n = 49), respectively.⁵ In a study of 251 patients with squamous cell carcinoma on sputum cytology, yet negative chest imaging, the 5-year and 10-year survival rates were 53.2% and 33.5%.⁶ Another study of 57 patients with potentially resectable disease who did not undergo surgery reported a median survival of 15.6 months, compared with 30.9 months for a group of 346 patients who underwent resection.⁷

PREDICTORS OF SURGICAL MORTALITY

Several large patient series describe perioperative mortality and the rate of complications for patients undergoing surgical resection for lung cancer. Reported surgical mortality rates in these studies vary from approximately 1% to 5%.^2,8–10 The median age of patients in most of these studies was 65 to 70 years, and many patients had significant medical comorbidity. Predictors of increased surgical mortality include pneumonectomy, bilobectomy, American Society of Anesthesiologists (ASA) Physical Status Scale rating, Zubrod performance status score, renal dysfunction, induction chemoradiation therapy, steroid use, older age, urgent procedures, male gender, forced expiratory volume in 1 second (FEV₁), and body mass index.¹¹ In France, a thoracic surgery scoring system for in-hospital mortality (Thoracoscore) was developed using data obtained from more than 15,000 patients who were enrolled in a nationally representative thoracic surgery database. Mortality risk factors included in the model were patient age, sex, dyspnea score, ASA score, performance status, priority of surgery, diagnosis, procedure class, and comorbid disease.¹² The model was highly accurate for the prediction of mortality, with a C statistic of 0.86. (1.00 corresponds to perfect outcome prediction.) The model was subsequently validated on 1,675 patients from the United States, where a similar accuracy was noted.¹³ The online version of the Thoracoscore risk assessment tool is available at: https://www.sfar.org/scores2/thoracoscore2.php.

REDUCED PULMONARY FUNCTION AFTER RESECTION

Several outcome measures have been used to assess the impact of resection on pulmonary function and quality of life after surgery. Across various studies, postoperative FEV₁ values, diffusing capacity of the lung for carbon monoxide (Dlco) values, and peak oxygen consumption (VO₂ peak) were assessed at various time intervals after lobectomy or pneumonectomy. FEV₁ varied from 84% to 91% of preoperative values for lobectomy,^14–16 and 64% to 66% for pneumonectomy.^14–16 The Dlco was 89% to 96% of preoperative values after lobectomy and 72% to 80% after pneumonectomy.^14,16 VO₂ peak varied from 87% to 100% of preoperative values after lobectomy,^14–16 and 71% to 89% after pneumonectomy.^14–16

Patients with chronic obstructive pulmonary disease (COPD) typically experience smaller declines in FEV₁ after lobectomy (0% to 8%) than those without COPD (16% to 20%). Declines in Dlco and VO₂ peak are more variable, with reported decreases of 3% to 20% in those with COPD, and 0% to 21% for those without the disease.^17–19

Lobectomy patients continue to recover pulmonary function for approximately 6 months after surgery. In patients who undergo pneumonectomy, improvement is generally limited after 3 months.^14–16 Loss of lung function may vary significantly with the location of the resection. For example, resection of an emphysematous portion of the lung will probably result in less loss of function.

Few studies specifically examine quality of life after lung resection in patients with lung cancer. In general, patients who undergo resection have a lower quality of life before surgery than the general population.²⁰ Postsurgical decline in physical measures of health-related quality of life has been reported during the month after surgery, with a return to baseline after 3 months. Mental quality of life scores did not decrease after surgery, and there was little correlation between quality of life outcomes and measures of pulmonary function.²⁰

LUNG FUNCTION TESTING

Lung function testing helps predict the risk of postoperative complications, including mortality. The two most commonly used measures of pulmonary function are FEV₁ and Dlco.

Both absolute FEV₁ value and percent of predicted FEV₁ strongly predict the risk of postoperative complications. It has been difficult to identify one cutoff value below which resection should not be considered. Studies have suggested preoperative absolute FEV₁ values of 2 L for pneumonectomy and 1.5 L for lobectomy as cutoffs signifying increased short- and long-term surgical risk.^21,22 Percent predicted FEV₁, which incorporates patient age, sex, and height, is more commonly used to individualize treatment, since absolute values do not take into consideration other patient-related variables. An FEV₁ of 80% predicted or higher has been proposed as a cutoff to proceed with resection without additional testing,²³ but this decision must be individualized to each patient.

Similarly, it has been difficult to identify one cutoff value for the Dlco. As one might expect, the lower the value the higher the risk for a given patient. Patients with Dlco values less than 60% predicted normal²⁴ had an increased mortality risk, longer hospital stay, and greater hospital costs in one report.

FEV₁ and Dlco are only modestly correlated with one another.²⁵ In one study, 43% of patients with FEV₁ greater than 80% of predicted had Dlco less than 80% of predicted.²⁶

According to guidelines developed by the American College of Chest Physicians (ACCP), spirometry is recommended for patients being considered for lung cancer resection.²⁷ Patients with FEV₁ that is greater than 80% predicted or greater than 2 L and without evidence of dyspnea or interstitial lung disease are considered suitable candidates for resection, including pneumonectomy, without further testing. Lobectomy without further evaluation may be performed if the FEV₁ is greater than 1.5 L and there is no evidence of dyspnea or interstitial lung disease.

Although assessing FEV₁ values alone may be adequate in patients being considered for lung cancer resection who have no evidence of either undue dyspnea on exertion or interstitial lung disease, the ACCP recommends also measuring Dlco when these signs are present. Guidelines from the European Respiratory Society (ERS) and the European Society of Thoracic Surgeons (ESTS) recommend routinely measuring Dlco during preoperative evaluation regardless of whether the spirometric evaluation is abnormal.²⁸ Similarly, the British Thoracic Society (BTS) recommends measuring transfer factor of the lung for carbon monoxide (Tlco) in all patients regardless of spirometric values.²⁹