Prolonged Survival in Lung Cancer Patients with Diabetes Mellitus

Abstract

We appreciate your interest in our article published in the Journal of Thoracic Oncology1Hatlen P Grønberg BH Langhammer A Carlsen SM Amundsen T Prolonged survival in patients with lung cancer with diabetes mellitus.J Thorac Oncol. 2011; 6: 1810-1817Abstract Full Text Full Text PDF PubMed Scopus (55) Google Scholar and thank you for the opportunity to answer your questions. In our article, we analyzed the influence of diabetes mellitus on the survival of patients with lung cancer. We found that lung cancer patients with diabetes mellitus had a longer survival compared with patients without diabetes mellitus. The mean age at baseline in the Nord-Trøndelag Health Study (HUNT) for patients with lung cancer was 59 years, and 4.5% among these had self-reported diabetes mellitus. Similar prevalence has been reported in other studies for comparable age groups,2Eliasson M Lindahl B Lundberg V Stegmayr B No increase in the prevalence of known diabetes between 1986 and 1999 in subjects 25-64 years of age in northern Sweden.Diabet Med. 2002; 19: 874-880Crossref PubMed Scopus (70) Google Scholar and these estimates are also in line with the prevalence in the total HUNT study population at this age.3Langhammer A Krogstad S Romundstad P et al.Participation and External Validfity in the HUNT Study in Norway.BMC Medical Research Methodology. 2012; (in press)PubMed Google Scholar,4Shaw JE Sicree RA Zimmet PZ Global estimates of the prevalence of diabetes for 2010 and 2030.Diabetes Res Clin Pract. 2010; 87: 4-14Abstract Full Text Full Text PDF PubMed Scopus (5017) Google Scholar The mean age at the time of diagnoses of lung cancer was 70 years. In the HUNT study, diabetes mellitus was defined by the answer “yes” to the question “Do you have or have you had diabetes?” independent of whether or not the person used medication for diabetes mellitus. Self-reported diabetes mellitus is a widely accepted and used tool in epidemiological studies.5Goldman N Lin IF Weinstein M Lin YH Evaluating the quality of self-reports of hypertension and diabetes.J Clin Epidemiol. 2003; 56: 148-154Abstract Full Text Full Text PDF PubMed Scopus (313) Google Scholar The question on self-reported diagnosis has also been validated in the HUNT study population.6Midthjell K Holmen J Bjørndal A Lund-Larsen G Is questionnaire information valid in the study of a chronic disease such as diabetes? The Nord-Trøndelag diabetes study.J Epidemiol Community Health. 1992; 46: 537-542Crossref PubMed Scopus (209) Google Scholar We therefore believe that our definition of the variable “diabetes mellitus” can be used in the current setting. Dr. Satoh is of course right regarding change in the treatment of diabetes mellitus in the last decades. We agree that information on whether patients had diabetes mellitus or not, closer to or at the time of diagnosis would have improved our study and reduced misclassification. This would, however, reduce nondifferential misclassification, and this should rather strengthen than weaken the report on associations. All participants in the HUNT study are identified with an eleven-digit national identification number that all Norwegians are given at birth or immigration. All data regarding HUNT participants are linked by this key, and no duplicate data set are present in the HUNT database. Diabetes mellitus was no exclusion criteria in the pemetrexed-gemcitabine study or in the Norwegian Lung Cancer Biobank (Norwegian Lung Cancer Biobank study, and the prevalence of diabetes mellitus was 3.9% (mean age 64 years) and 8.1% (mean age 68 years), respectively. Therefore, we have no indication of diabetes mellitus being the cause of any selection bias in the PEG or NLCB study. In these studies, we used the medical journal to identify whether patients had diabetes mellitus or not.