Japanese researchers have developed a novel technique using balloon dilation that allows bronchoscopes to pass deeper into the lungs, improving diagnostic sensitivity for small peripheral pulmonary lesions (PPLs).
The balloon dilatation for bronchoscope delivery (BDBD) technique “may challenge the conventional belief that bronchoscopes cannot reach the peripheral lung field, introducing a new strategy to improve diagnostic yield,” write Kotaro Miyake, MD, PhD, a professor in the Department of Respiratory Medicine and Clinical Immunology at Osaka University in Japan, and co-authors in Thorax.
They explain that although endoscopic biopsy is highly effective for pulmonary lesions exposed within the central airways, diagnosing PPLs—abnormal areas of tissue located near the outer edges of the lung, away from the central airways—is challenging because conventional bronchoscopes are too large to directly reach the narrow outer airways.
Methods have been developed to overcome this challenge, including the use of transthoracic needle aspiration, which has high diagnostic sensitivity but also a high risk for pneumothorax and bleeding, and robot-guided transbronchial biopsy (TBB), which requires complex equipment and comes at a high cost.
Miyake and team therefore set out to find a simpler solution and proposed the BDBD technique as a novel approach to improve TBB by enabling direct visualization and biopsy of peripheral lesions, like endobronchial biopsy for central airway lesions.
“In most medical fields, balloon dilation is generally performed to treat pathological stenosis—such as in coronary arteries, cerebral vessels, or the esophagus,” Miyake told Inside Precision Medicine. “Even in pulmonology, balloon dilation is occasionally used for pathological airway stenosis.”
He explained: “The novel concept behind the BDBD method is that we dilate normal bronchi, not diseased ones, to improve the accuracy of transbronchial biopsy. This idea—using dilation proactively to enhance navigation and sampling rather than to treat stenosis—is, in my opinion, what makes this technique new.”
They tested the technique in a first-in-human trial that included 22 patients with PPLs measuring smaller than 20 mm (mean 15.3 mm) that were visibly connected to a bronchus on computed tomography. The patients underwent bronchoscopy with ultrathin or thin bronchoscopes under conscious sedation and when the bronchoscope could not advance further, the balloon was dilated to open the airway and allow the bronchoscope to move closer to the target where biopsies were taken.
Of the 22 patients who underwent bronchoscopy with the BDBD technique, 18 were ultimately diagnosed with cancer. BDBD enabled bronchoscope advancement in all 18 cases and allowed direct biopsy site visualization in 17 cases.
The technique detected cancer in 14 of the 18 patients with a confirmed diagnosis, giving a diagnostic sensitivity of 77.8%.
By comparison, Miyake estimated that, in general, “the diagnostic yield of conventional bronchoscopy is typically around 60–70% for PPLs smaller than 20 mm and it is uncommon for yields to exceed 70% in this size range.” However, he stressed that this may vary widely depending on patient background, lesion characteristics, and procedural techniques.
The researchers report that, on average, using the BDBD technique allowed the bronchoscope to pass through an additional 2.3 branching points, or bifurcations, within the bronchi of the lungs without any significant adverse events. This meant the depth extended from 5.7 to 8.0 bronchial generations with an ultrathin bronchoscope and 3.5–4.0 mm balloon, and from 4.0 to 6.6 bronchial generations with a thin bronchoscope and 4.0–5.0 mm balloons.
“Even advancing by a single bifurcation is clinically meaningful, so 2.3 bifurcations is highly significant,” said Miyake.
There were no severe adverse events with BDBD, but the researchers stress that X-ray fluoroscopy is crucial to confirm balloon positioning and prevent pneumothorax. They also recommend avoiding inflating the balloon with air or water near the pleura.
Longer-term evaluations of the safety of the BDBD technique and a randomized controlled trial to clearly demonstrate improvement in diagnostic yield, as well as further investigation to optimize its indications and applications, will be needed before the technique is widely adopted.
Nonetheless, “the BDBD catheter has already been approved and is currently being used in daily clinical practice in Japan,” said Miyake. “Our next goals are to promote its implementation nationwide and to publish additional clinical data. Ultimately, we hope that the technique will be adopted internationally.”
