Does virtual bronchoscopic navigation improve the diagnostic yield of transbronchial biopsy?

Transbronchial biopsy (TBB) is performed for diagnosis of peripheral pulmonary lesions because it is generally safe with a low incidence of complications. However, the diagnostic yield in small peripheral lesions is poor. The diagnostic sensitivity of TBB by conventional bronchoscopy for lung lesions smaller than 2 cm is approximately 34%.1

Virtual bronchoscopic navigation (VBN) is a method in which the bronchoscope is guided to a peripheral lung lesion under direct observation using virtual bronchoscopic images. VBN can be used for computed tomography (CT)-guided ultrathin bronchoscopy, endobronchial ultrasound using a guide sheath (EBUS-GS) and conventional bronchoscopy with X-ray fluoroscopy. Previously published overall diagnostic yields using VBN and that of 2 cm or smaller lesions were 73.8% and 67.4%, respectively.2 These outcomes compare to a 72% diagnostic yield for use of VBN as reported by meta-analysis.3 The greater diagnostic yield of peripheral pulmonary lesions using bronchoscopy with VBN is therefore significant; there is no need for an expensive disposable electromagnetic sensor as is the case for electromagnetic navigation (EMN),4 and it can be easily performed.

In a recent publication in Respirology, Kato et al. present a randomized controlled study demonstrating that VBN increases the diagnostic yield for CT-guided transbronchial biopsy (CT-TBB).5 The study focused on patients with CT-bronchus sign (CT-BS)-positive lesions, which were smaller than 2 cm with a low diagnostic yield on conventional bronchoscopy and located in the peripheral one-third of the lung. In this study, the use of VBN for CT-TBB significantly improved the diagnostic yield, which reached 84%.

Two other randomized controlled trials of VBN have been performed. Ishida et al. reported that the diagnostic yield on bronchoscopy with EBUS-GS and X-ray fluoroscopy of 3 cm or smaller peripheral pulmonary lesions was significantly improved (from 67.0% to 80.4%) by concomitant use of VBN.6 In their study, both the time to the start of biopsy and the total examination time were shortened. Asano et al. reported that concomitant use of VBN in bronchoscopy of 3 cm or smaller peripheral lesions using a 2.8-mm ultrathin bronchoscope and X-ray fluoroscopy increased the diagnostic yield from 59.9% to 67.1%. However, the increase was not significant and the diagnostic yield of lesions located in the peripheral one-third of the lung was significantly improved in sub-analysis,7 as also reported in the current study.5

Therefore, VBN increases the diagnostic yield of small peripheral pulmonary lesions. A key question is with what technique should VBN be combined? There are three points to increase the diagnostic yield of TBB: navigation by bronchoscope and biopsy instrument to a lesion, confirmation of the presence of biopsy instrument at the lesion and collection of a sufficient amount of specimen using biopsy. CT-TBB is useful to confirm the presence of biopsy forceps as does EBUS. On the other hand, CT fluoroscopy presents individual axial images but location of the bronchoscope and biopsy forceps cannot be displayed on one image in real time (unlike X-ray fluoroscopy), so that the positional relationship between the bronchoscope and lesion cannot be readily identified. Moreover, frequency of CT scanning must be limited to reduce radiation exposure. Therefore, CT alone may be inappropriate for navigation.

In sub-analysis of the data collected by combination with EBUS-GS, VBN significantly increased the diagnostic yield of CT-BS-positive lesions smaller than 2 cm from 70.7% to 94.6%,8 although these findings cannot be directly compared with that of the present study.5 Furthermore, Oki et al. reported that the histological yield of 3 cm or smaller peripheral lesions was 74% when radial EBUS, ultrathin bronchoscope and VBN were used together. The authors concluded that the combination of VBN and ultrathin bronchoscopy is optimal.9

Cone beam CT has recently been used also for bronchoscopy,10 and cone beam CT-TBB use may increase because of low radiation exposure11 and convenience of X-ray fluoroscopy. As stated by Kato et al., TBB is safe and effective when used in combination with VBN for CT-BS-positive lesions (even small lesions), but further investigations are necessary.