New Nodal Descriptor Classification Potentially Better at Differentiating Patients

New Nodal Descriptor Classification Potentially Better at Differentiating Patients

Staging
Jan 29, 2021
Figure 1: New Nodal Descriptor Classification Potentially Better at Differentiating Patients

The IASLC’s proposed new classification of N descriptor is potentially better at differentiating patients with lung cancer into different stages, according to the results of a study presented during the mini oral session, “MA09: Prognosis and Staging,” held on Sunday. 

According to a presentation by Dariusz Dziedzic, MD, National Research Institute of Chest Diseases, Warsaw, Poland, the IASLC has proposed the classification of the N descriptor be based on the number of nodal stations and skip metastases. The new classification would divide into subgroups N0, N1a (N1 single station), N1b (more than one N1 station), N2a1 (N2 single with skip metastasis), N2a2 (N2 single without skip metastasis), and N2b (more than one N2 station). 

Dr. Dziedzic and colleagues conducted a retrospective study to try to assess the impact of the number of lymph nodes removed on the newly suggested classification system. 

“There is no consensus about the number of lymph nodes that should be dissected during surgery,” Dr. Dziedzic said. “Some suggest that between 10 and 16 lymph nodes should be resected. We chose the number 6 in our study, which is in our opinion the optimal number.”

In the retrospective study, Dr. Dziedzic and colleagues included 8,016 patients with NSCLC from the Polish Lung Cancer Study Group. To be included patients had confirmed NSCLC, R0, lymphadenectomy or lymph node sampling and complete clinical data. For the study, patients were divided into two groups: those with 6 or fewer lymph nodes removed (1,909 patients) and those with more than 6 lymph nodes (6,107 patients). 

Final results showed that, with the current classification, the difference in survival curves between classification groups was not visible or very small. However, with the proposed new classification, we can see statistically significant difference between each substage. 

For example, 5-year survival rates for N0 classification using the new classification was 55.1% for 6 or fewer lymph nodes removed compared with 62.3% for more than 6 lymph nodes removed (p < 0.001). There was also a significant difference from N2a1 (26.3% vs. 37.3%; p = 0.022). In the N1 category, the difference was almost significant (33.9% vs. 41.7%; p = 0.058). 

Using the proposed classification for N0, N1a, N1b, N2a1, N2a2, N2b1, and N2b2 in patients with six or fewer lymph nodes removed survival was 55.1%, 35.9%, 31.7%, 26.3%, 26.7%, 29.2%, 22.0%, respectively; in the group with more than six lymph nodes removed, they were 62.3%, 44.5%, 34.1%, 37.3%, 32.4%, and 29.4%, and 23.0%. 

Dr. Dziedzic concluded that although this new classification is potentially better at differentiating patients into different stages, the accuracy of the classification depends on the number of lymph nodes removed. Therefore, the extent of lymphadenectomy has a significant impact on the staging of surgically treated lung cancer. 

“One of the most important prognostic factors for lung cancer is nodal staging,” said study discussant Kenji Suzuki, MD, of Juntendo University, Japan. “Lung cancers that involve the nodes should be resected completely by thoracic surgeons.” 

On the other hand, he said, involvement of the nodes cannot be disclosed based on nodal dissection or sampling. Dr. Suzuki showed data from a study of the North American National Cancer Database that showed that nodal investigation was done in just 56% of patients, even for stage IIIa NSCLC. 

“This fact should be improved in the thoracic community,” Dr. Suzuki said. 

In Dr. Dziedzic’s study, they found that more than 6 dissected nodes were better than 6 or less for lung cancer, Dr. Suzuki said. They also fold that proposed descriptor was better than current staging.

“In the near future, a well-planned prospective study comparing involved number of nodes and stations should be performed,” he said. 

This session had a real-time Q&A that provided attendees with the opportunity to ask questions of the session participants. The Q&As are included in the On-Demand recordings, available through the virtual platform. Registration is ongoing for the next 60 days at wclc2020.iaslc.org

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