Lymph node involvement and metastatic lymph node ratio influence the survival of malignant pleural mesothelioma: a French multicenter retrospective study

Our plain-English summary of Lymph node involvement and metastatic lymph node ratio influence the survival of malignant pleural mesothelioma: a French multicenter retrospective study, by I. Hysi, F. Le Pimpec-Barthes, M. Alifano, et al (Oncology Reports, 2014).

The study

• Authors: I. Hysi, F. Le Pimpec-Barthes, M. Alifano, N. Venissac, J. Mouroux, J.F. Regnard, M. Riquet, H. Porte
• Journal: Oncology Reports
• Published: 2014;31(1):415-21
• Cited by: 14 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Malignant pleural mesothelioma (MPM) is a rare tumor with disastrous evolution. The prognostic value of nodal involvement is still debated. We analyzed the impact of nodal involvement on overall survival (OS) in patients treated by multimodal therapy including extra pleural pneumonectomy (EPP). We evaluated the role, as a prognostic factor, of the metastatic lymph node ratio (LNR), corresponding to the number of involved nodes out of the total number of removed nodes. In this retrospective multicentric study, we reviewed the data of 99 MPM patients. Information regarding lymph node involvement was assessed from the final pathology reports. N1-N3 patients were pooled as N+ group. The OS, calculated by the Kaplan-Meier method, was compared using the log-rank test. A multivariate Cox proportional hazards model was used to identify independent prognostic factors. For the whole cohort, median OS was 18.3 months and 5-year survival was 17.5%. N+ status reduced significantly the median survival (22.4 months for N0 patients vs 12.7 months for N+ patients, P=0.002). A lower metastatic LNR (≤13%) was associated with a significantly improved median survival (19.9 vs. 11.7 months, P=0.01). OS was not related to the number of involved or total removed lymph nodes. In multivariate analysis, only adjuvant radiotherapy (P=0.001) was identified as an independent positive prognostic factor. Metastatic LNR is a more reliable prognostic factor than the number of involved lymph nodes or the total number of removed nodes. However, it could not be identified as an independent prognostic factor.

In plain English

This retrospective study reviewed records of 99 patients with malignant pleural mesothelioma treated between December 1997 and September 2010 at four French university thoracic surgery departments. All underwent extrapleural pneumonectomy as part of combined treatment. The authors examined whether cancer in the lymph nodes, and the lymph node ratio (the share of removed nodes containing cancer), was related to survival. Median overall survival for the whole group was 18.3 months, and 5-year survival was 17.5%. Median survival was 22.4 months for patients without node involvement and 12.7 months for those with it. Patients with a ratio of 13% or less had a median survival of 19.9 months, compared with 11.7 months for those above 13%. This difference disappeared when only node-positive patients were compared. In the multivariate analysis, only adjuvant radiotherapy was an independent factor, and the ratio was not statistically significant. The authors suggested the ratio may play a role in future assessment of these patients, to be confirmed by larger prospective studies. They noted the retrospective design and possibly insufficient statistical power.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Retrospective multicenter study of patient records (survival analysis)
• Who was studied: 99 patients with biopsy-diagnosed malignant pleural mesothelioma who underwent extrapleural pneumonectomy with curative intent, treated December 1997 to September 2010 in four French university hospital thoracic surgery departments (two in Paris, one in Nice, one in Lille)
• Exposure: The factors analyzed were lymph node status (N0 versus N1 to N3 pooled as N+) and the metastatic lymph node ratio. Asbestos exposure was only recorded as a patient characteristic: Table I lists 75 (81.5%) patients with asbestos exposure. Listed occupations included building worker (18) and steelworker (13). No fiber types or doses were reported.
• Main results:
  • For the whole cohort, median overall survival was 18.3 months and 5-year survival was 17.5%.
  • Nodal status: 65 (65.6%) N0, 3 (3.1%) N1, 30 (30.3%) N2 and 1 (1%) N3.
  • Median survival was 22.4 months for N0 patients versus 12.7 months for N+ patients (P=0.002).
  • Patients with a metastatic lymph node ratio of 13% or less had a median survival of 19.9 months, compared with 11.7 months for those above 13% (P=0.01). 75 (75.7%) patients had a ratio of 13% or less.
  • Within the subgroup of N+ patients, the survival difference by lymph node ratio disappeared (P=0.88).
  • Overall survival was not related to the number of involved lymph nodes or the total number of removed lymph nodes.
  • In multivariate analysis, only adjuvant radiotherapy was an independent prognostic factor. The lymph node ratio did not reach statistical significance.
  • In an exploratory analysis, N0 patients who received adjuvant radiotherapy had a median overall survival of 38 months and 5-year survival of 35.8%. N+ patients without adjuvant radiotherapy had 8 months and 0%.
  • 30-day mortality after surgery was 8% and 90-day mortality was 14.1%.
• The authors' conclusion: The authors suggested that the metastatic lymph node ratio is likely to play a role in the future assessment of malignant pleural mesothelioma patients, and that this should be confirmed by larger prospective studies. They noted the ratio failed to reach full statistical significance in the multivariate analysis.
• Limitations the authors state:
  • Retrospective design, introducing heterogeneity, such as some patients receiving tetramodal therapy with hyperthermic intrathoracic chemotherapy instead of standard trimodal therapy
  • Statistical power may be insufficient despite 99 patients, partly because of the relatively small number of N+ patients (34.3%)
  • Recurrence information was incomplete
  • Patients were studied over a 13-year period, possibly adding heterogeneity
  • Pathology was done at four different centers, a possible source of non-uniformity

Topics

The National Library of Medicine indexes this study under subjects our site covers: Lung cancer, Mesothelioma.

Medical terms in this study, explained in our Lexicon: Pleural Mesothelioma, Overall Survival, Multimodal Therapy, Pneumonectomy, Pathology Report, Median Survival, Multivariate Analysis.

Related studies

• Hyperplastic mesothelial cells in lymph nodes: report of six cases of a benign process that can stimulate metastatic involvement by mesothelioma or carcinoma — P. Argani, J. Rosai (1998)
• Clinical and pathological characteristic of metastatic malignant mesothelioma initially diagnosed by lymph node biopsy — X.L. Zhu, L.M. Gao, et al. (2017)
• Lymph node metastases in diffuse malignant peritoneal mesothelioma — D. Baratti, S. Kusamura, et al. (2010)
• Posterior Intercostal Lymph Nodes Double Recurrence and Death Risk in Malignant Pleural Mesothelioma — J.S. Friedberg, C.B. Simone, et al. (2020)
• Diagnosis of malignant pleural mesothelioma by axillary lymph node biopsy — S.B. Kim, B. Varkey, et al. (1987)
• Fine-needle aspiration biopsy of axillary lymph nodes — S. Jaffer, M. Zakowski (2002)

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