Trial Information

Value of EBUS-TBNA for Mediastinal Lymph Nodes in Non-small Cell Lung Cancer in a Tuberculosis-endemic Country

Lung cancer remains a fatal disease worldwide, and surgical treatment offers possibility for
long-term survival. However, the indication and outcome of surgical resection depends on the
pre-operative accurate staging and extent of intra-operative lymph node dissection.
Therefore, the accurate lymph node staging in non-small cell lung cancer (NSCLC) is crucial
for planning optimal treatment. Traditionally, the conventional contrast-enhanced CT
essentially identifies enlarged lymph node greater than 1cm as nodal metastasis.
Nevertheless, with moderate sensitivity and specificity, contrast-enhanced CT carries
substantial risk to under-stage small nodal metastasis and to over-stage inflammatory
lymphadenitis.

Positron emission tomography (PET) with fluorine-18 fluorodeoxyglucose (FDG) provides
functional images of tumor metabolism, and has been used as a non-invasive alternative other
than contrast-enhanced CT for nodal staging in NSCLC. In the absence of detectable lymph
node enlargement by CT, FDG-PET scan were increasingly used to stage the lymph node status
for NSCLC in some part of world. Hence, the accuracy of FDG-PET might substantially alter
the treatment strategy in an institution where the mediastinoscopy is unavailable for lymph
node sampling. However, it is generally agreed that abnormal FDG uptake occurred frequently
in granulomatous and inflammatory disease. In an endemic area where tuberculosis is still
prevalent; such as Eastern Asia, FDG-PET scan has reportedly shown reduced sensitivity and
positive predictive value in nodal staging of NSCLC. Thereby, FDG-PET scan alone does not
appear to replace mediastinoscopy for nodal staging of NSCLC in a tuberculosis-endemic
area, especially in potentially operable patients without enlarged mediastinal lymph nodes.

The recent development of curved ultrasound probe-equipped bronchoscope, which enables
direct and real-time aspiration by endobronchial ultrasound- transbronchial needle
aspiration (EBUS-TBNA) of mediastinal and hilar lymph nodes, has become an less invasive
alternative for nodal staging other than mediastinoscopy. By direct nodal sampling,
EBUS-TBNA improves lymph node staging from an image basis to a cytology basis; or even,
pathology basis. However, the variable sensitivity and negative predictive value of
EBUS-TBNA has been reported, especially in lymph node reduced in size after induction
chemotherapy. Nevertheless, reports from NSCLC without significant mediastinal lymph node
enlargement on CT otherwise suggested EBUS-TBNA exhibited a high sensitivity and specificity
for detecting small nodal metastasis. Therefore, whether EBUS-TBNA retains the reportedly
high performance of nodal staging in lung cancer patients without enlarged mediastinal lymph
node on CT in a TB endemic country; a condition of FDG-PET scan reportedly showed increased
false-positive rate, is still unclear.

In present study, we primarily aim at the comparison of accuracy of nodal diagnosis of
contrast-enhanced CT and PET scan with and without EBUS-TBNA in a condition of mediastinal
and hilar lymph nodes of lung cancer. Secondarily, we aim at the accuracy of nodal diagnosis
by FDG-PET scan in the same condition, and investigate the characteristics of lymph nodes
with false PET result.