PET/CT depiction of ATS mediastinal nodal stations: What every radiologist should know - diagnostic strategies and potential pitfalls

Transcription

1 PET/CT depiction of ATS mediastinal nodal stations: What every radiologist should know - diagnostic strategies and potential pitfalls Poster No.: C-236 Congress: ECR 2009 Type: Educational Exhibit Topic: Chest Authors: J. V. Raj, J. Birchall ; Leicester/UK, Derby/UK Keywords: PET/CT, ATS nodal Station DOI: /ecr2009/C Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 19

2 Learning objectives Understand the importance of using ATS (American Thoracic Society) nodal stations nomenclature in staging lung cancer. Appreciate PET/CT depiction of these nodal stations. Highlight potential pitfalls and important diagnostic strategies in use of PET/CT for staging lung cancer. Background Detection and depiction of pathological nodes are essential for accurate staging, assigning treatment, predicting prognosis and evaluating efficacy of treatment in patients with lung cancer. Definitions of lymph node locations traditionally have been based on surgical landmarks relevant to mediastinoscopy and throacotomy. Translating and adopting these surgical landmarks used for ATS system into cross sectional imaging can be challenging. In PET/CT this handicap is less obvious due to the ability of multi planar reconstructions. It is vital that radiologists, nuclear medicine physicians, pulmonologists, thoracic surgeons and oncologists speak the same language and use a common system when it comes to nodal staging. This can only be achieved by universal use of American Thoracic Society (ATS) system. Imaging findings OR Procedure details ATS nodal system ATS regional lymph node system distributes thoracic nodes into fourteen numbered stations. All N2 nodes are contained within mediastinal pleural envelope and are numbered 1 to 9. Hilar and intrapulmonary nodes (N1) lie within the visceral pleura and are numbered 10 to 14. According to location of primary tumour, ipsilateral nodes are designated right or left, midline prevascular and retro-tracheal lymph nodes are considered ipsilateral. Page 2 of 19

3 Fig.: Mountain/Dresler modifications from Naruke/ATS-LCSG Mapc 1997 Reprints are permissible for educational use only Depending on the side of the known primary non small cell lung cancer, one can rapidly assess nodal (N) staging as shown in this table: Page 3 of 19

4 N staging of Right NSCLC based on ATS system N Stage SITE OF PRIMARY N1 N2 N3 ATS STATIONS INVOLVED RIGHT 10 R TO 14 R LEFT 10 R TO 14 R RIGHT 1R, 2R, 3, 4R, 7, 8I & 9I LEFT 1L, 2L, 3, 4L, 5, 6, 7, 8I &9I RIGHT 1L, 2L, 4L, 5, 6, 8C & 9C LEFT 1R, 2R, 4R, 8C & 9C I= Ipsilateral C= Contralateral Station 1 to 9 Traditionally these have been defined as N2 station nodes i.e contained within mediastinal pleural envelope. However, these nodal stations should not be confused with TNM nodal staging for Non Small Cell Lung Cancer (NSCLC) as involvement of these nodes can indicate either N2 or N3 stage depending on the site of primary tumour. In clinical practice Station 1 to 3 are routinely (although wrongly) clubbed together and called prevascular or higher mediastinal nodes. Page 4 of 19

5 Fig.: High Right mediastinal node Station 2 and 4 have significant diagnostic importance and should be clearly identified and documented. Along with St 7 these nodes are accessible for Endobronchial Ultrasound (EBUS) sampling. Appropriate use of this system helps in deciding next appropriate step in nodal sampling i.e mediastinoscopy, medistinotomy or EBUS. Page 5 of 19

6 Fig.: Axial and coronal representation of station 2 Page 6 of 19

7 Fig.: Right paratracheal node with a right upper lobe lung mass Page 7 of 19

8 Fig.: Subaortic and para aortic node Page 8 of 19

9 Fig.: Subaortic/Paraaortic Station 10 to 14 These are classically localed within visceral pleura and in clinical practice many people club them into hilar or intrapulmonary group. Page 9 of 19

10 Fig.: Coronal image demonstrating 10 R and L nodes Page 10 of 19

11 Fig.: Left hilar node Controversies, Pitfalls and Diagnostic strategy 1. As illustrated in the recent publication from the International Association for the Study of Lung Cancer (IASLC) regarding proposed changes to the TNM staging system for NSCLC, there is lack of uniformity in use of ATS system worldwide. In general, Japanese tend to use Naruke lymph node map while other countries use the Mountain Dressler modification. In the former, lymph nodes in the subcarinal space along the inferior border of the mainstem bronchus is considered to be at station 10 (i.e N1) but in the latter they are said to be at 7 and therefore N2. Page 11 of 19

12 2. Fig.: T3 tumour with right subcarinal node. This could be classified as N1 or N2 depending on the system used. PET/CT has limited spatial resolution and every clinician who is involved in the use of this technique needs to be aware of this. On the other hand, everything hot on PET is not tumour. Infection, inflammation, fat necrosis etc. Page 12 of 19

13 3. Fig.: Node without any FDG uptake. This could be secondary to limited spatial resolution or benign nature Benign nodes with characteristic fatty hila do not take up FDG. Page 13 of 19

14 4. Fig.: CT showing characteristic fat and no FDG uptake on PET/CT Nodal involvement in malignancy tends to spread in a step wise manner i.e, N1 followed by N2 and then N3. In an unusual clinical scenario of N3 uptake without N1/N2 involvement, nodal sampling should be performed prior to making any important therapeutic decisions. Images for this section: Page 14 of 19

15 Fig. 1: Mountain/Dresler modifications from Naruke/ATS-LCSG Mapc 1997 Reprints are permissible for educational use only Page 15 of 19

16 Fig. 2: Node without any FDG uptake. This could be secondary to limited spatial resolution or benign nature Page 16 of 19

17 Fig. 3: Coronal image demonstrating 10 R and L nodes Page 17 of 19

18 Fig. 4: Subaortic and para aortic node Page 18 of 19

19 Conclusion PET/CT has an ever improving and expanding role in management of thoracic malignancy. Every radiologist should therefore be well versed with the limitations of PET/ CT and use ATS nodal stations innormal clinical reporting. Personal Information References Mountain CF, Dresler CM. Regional lymph node classification for lung cancer staging. Chest 1997; 111: Jane P. Ko, Elizabeth A. Drucker, Jo-Anne O. Shepard, Clifton F. Mountain, Carolyn Dresler, Bradley Sabloff, and Theresa C. McLoud. CT Depiction of Regional Nodal Stations for Lung Cancer Staging Am. J. Roentgenol. Mar 2000; 174: Gustav K. von Schulthess, Hans C. Steinert, Thomas F. Hany. Integrated PET/CT: Current Applications and Future Directions. Radiology: February Volume 238: Number 2; Page 19 of 19