Comparison of coronal and axial computed tomography measurements of mediastinal nodes before primary surgery for non-small cell lung cancer

Impact of coronal and sagittal views on lung gross tumor volume delineation

BACKGROUND AND PURPOSE

To study the impact of coronal and sagittal views (CSV) on the gross tumor volume (GTV) delineation on CT and matched PET/CT scans in non-small cell lung cancer.

MATERIAL AND METHODS

GTV delineations were performed by 11 experienced radiation oncologists on CT and PET/CT in 22 patients. Two tumor groups were defined: Group I: Primary tumors surrounded by lung or visceral pleura, without venous invasion, and without large extensions to the chest wall or the mediastinum. Group II: Tumors invading the hilar region, heart, large vessels, pericardium, and the mediastinum and/or associated with atelectasis. Tumor volumes and inter-observers variations (SD) were calculated and compared according to the use of axial view only (AW), axial/coronal/sagittal views (ACSW) and ACSW/PET (ACSWP).

RESULTS

CSV were not frequently used (57.4% out of 242 delineations on CT). For group I, ACSW didn't improve significantly mean GTVs. SDs were small on CT and on PET (SD=0.3cm). For group II, ACSW had 27-46% smaller observer variation (mean SD=0.7cm) than AW (mean SD=1.1cm). The smaller observer variation of ACSW users was associated with, on average, a 40% smaller delineated volume (p=0.038). Mean GTV of ACSWP was 21% larger than mean GTV of ACSW on CT.

CONCLUSIONS

For smaller lung tumors surrounded by healthy lung tissue the effect of multiple axis delineation is limited. However, application of coronal and sagittal windows is highly beneficial for delineation of more complex tumors, with atelectasis and/or pathological lymph nodes even if PET is used.

Mediastinal and Hilar Lymph Node Measurements. Comparison of Multidetector-Row Computed Tomography and Endobronchial Ultrasound

RATIONALE

Multidetector-row chest computed tomography scan is a common initial imaging modality and endobronchial ultrasound is a minimally invasive diagnostic tool used to evaluate enlarged lymph nodes, but comparisons of imaging results are lacking.

OBJECTIVES

To determine the size of thoracic lymph nodes and the strength of agreement between each measurement from coronal plane computed tomography and static endobronchial ultrasound images.

METHODS

A retrospective review of consecutive patients who underwent endobronchial ultrasound-transbronchial needle aspiration of their lymph nodes because of clinical suspicion of benign or malignant thoracic disease.

MEASUREMENTS AND MAIN RESULTS

One hundred and twenty-four lymph nodes from the mediastinal (74.2%) and hilar (25.8%) stations were measured in 59 patients (mean age, 64.5 yr; 33 males). The mean (standard deviation) short-axis diameter on computed tomography was 14.1 (6.7) mm compared with 12.6 (6.6) mm on endobronchial ultrasound. Benign lymph nodes (n = 42) were larger on computed tomography than on endobronchial ultrasound (14.1 [6.2] vs. 11.5 [6.2] mm). Malignant lymph nodes (n = 35) were larger on endobronchial ultrasound than on computed tomography (17.3 [6.4] vs. 16.2 [6.7] mm). Sixty-five percent of the lymph nodes that were initially interpreted as not enlarged on axial computed tomography images measured greater than 10 mm on each imaging modality (12.5 [5.9] mm on computed tomography and 10.5 [5.6] mm on endobronchial ultrasound) and 24% of the sampled lymph nodes from this group contained malignant cells. Random-effects maximal likelihood linear regression showed a statistically significant difference between endobronchial ultrasound and the computed tomography method for measuring short-axis diameter in all 124 lymph nodes. There was a weak agreement (intraclass correlation, rho: 0.44 [95% confidence interval, 0.31-0.59]) between short-axis diameter measurements from each imaging modality.

CONCLUSIONS

Our single-center study shows that there was poor correlation between computed tomography and endobronchial ultrasound for the measurement of mediastinal and hilar lymph nodes. Malignant cells were recovered by ultrasound-guided needle aspiration from a substantial fraction of lymph nodes that were initially interpreted as normal in size. If these findings are confirmed, new criteria may be needed for lymph node measurement on computed tomography that will guide selection of lymph nodes for endobronchial ultrasound-transbronchial needle aspiration.

Unidimensional Measurement May Evaluate Target Lymph Nodal Response After Induction Chemotherapy for Nasopharyngeal Carcinoma

The aim of the study was to evaluate whether short axis and long axis on axial and coronal magnetic resonance imaging planes would reflect the tumor burden or alteration in size after induction chemotherapy in nasopharyngeal carcinoma. Patients with pathologically confirmed nasopharyngeal carcinoma (n = 37) with at least 1 positive cervical lymph node (axial short axis ≥15 mm) were consecutively enrolled in this prospective study. Lymph nodal measurements were performed along its short axis and long axis in both axial and coronal magnetic resonance imaging planes at diagnosis and after 2 cycles of induction chemotherapy. In addition, lymph nodal volumes were automatically calculated in 3D treatment-planning system, which were used as reference standard. Student's t test or nonparametric Mann-Whitney U test was used to compare the continuous quantitative variables. Meanwhile, the κ statistic and McNemar's test were used to evaluate the degree of agreement and discordance in response categorization among different measurements. Axial short axis was significantly associated with volumes at diagnosis (P < 0.001). A good agreement (κ=0.583) was found between axial short axis and volumetric criteria. However, the inconsistent lymph nodal shrinkage in 4 directions was observed. Axial short-axis shrinking was more rapid than the other 3 parameters. Interestingly, when utilizing the alternative planes for unidimensional measurements to assess tumor response, coronal short-axis showed the best concordance (κ=0.792) to the volumes. Axial short axis may effectively reflect tumor burden or change in tumor size in the assessment of target lymph nodal response after induction chemotherapy for nasopharyngeal carcinoma. However, it should be noted that axial short axis may amplify the therapeutic response. In addition, the role of coronal short axis in the assessment of tumor response needs further evaluation.