A meta-analysis of 40 studies of FDG PET scanning for solitary pulmonary nodules yielded a maximum joint sensitivity and specificity of 90% (95% CI, 86.4%– 92.7%).14 The methodological quality of studies included in the meta-analysis was fair, with small sample sizes (inclusion criteria were for a minimum of 10 patients with pulmonary nodules and malignant prevalence of at least 0.5); masking was frequently incomplete.
Sensitivity of histologic/cytologic tests varies
A recent systematic review of studies evaluating patients with suspected lung cancer looked into the diagnostic sensitivity of various methods of histologic and cytologic tests.15 Researchers compared the evaluated test results to a reference standard of pathology/histology, definitive cytology, or at least 1-year radiographic follow-up.
Transbronchial needle aspiration showed a sensitivity of 67% (95% CI, 64%–70%) for peripheral lung malignancy of any size; however, only 5 studies met study criteria and their sample sizes varied greatly (n=20 to n=480). Eight studies looking at bronchoscopy (including brush or biopsy) for peripheral lung lesions <2 cm in diameter yielded a sensitivity of only 33% (95% CI, 28%–38%). In the same systematic review, 61 studies of transthoracic needle aspiration for localized pulmonary lesions of any size had a pooled sensitivity of 90% (95% CI, 88%–92%). The prevalence of malignancy in the studies ranged from 0.58 to 0.93.15 Factors affecting heterogeneity between studies included the wide range in study dates, imaging technology used, and study sizes.
What test is most cost-effective?
CT appears cost-effective when the pretest probability of malignancy is <90%; therefore, consider it on virtually all new cases of solitary pulmonary nodules.1 Also, when CT and pretest risk-assessments are discordant (eg, a patient has a low pretest probability of malignancy but his CT is suggestive of malignancy), the FDG PET scan is the most economically feasible at less than $20,000 per quality-adjusted life year.
Recommendations from others
The American College of Chest Physicians (ACCP)2 suggests pursuing no further evaluation if a nodule is unchanged for >2 years or has benign central calcifications. They recommend that physicians perform CT on every patient with a new nodule to characterize the nodule, its location, and the mediastinum. They do not recommend PET scans for nodules <1 cm. Patients who are marginal surgical candidates and have a negative PET scan should have a repeat CT scan in 3 months; serial CTs at 3, 6, 12, and 24 months are suggested, too, if prior chest radiographs are negative.
The ACCP states that transthoracic needle aspiration is not indicated in surgical candidates unless they decline surgery; then transthoracic needle aspiration or a transbronchial approach are the preferred procedure. Transthoracic needle aspiration may also be useful in establishing a diagnosis for patients who are not surgical candidates or who have a high surgical risk.
ACCP expert consensus favors the reference standard of video-assisted thoracoscopic surgery with wedge resection as the ideal method for obtaining tissue diagnosis in consenting, operable patients with solitary pulmonary nodules. Objective evidence is lacking on follow-up monitoring methods for patients with a nodule who do not have a tissue diagnosis and observation alone is chosen. ACCP expert consensus favors a 2-year follow-up with CT scanning at 3, 6, 12, and 24 months to monitor for nodule growth.2