50 Chapter 4 Materials and methods A cohort of Dutch patients who underwent lung surgical resection for pT3N0M0 NSCLC was retrieved from the IKNL for the 4-year period from 2010 to 2013, after the introduction of the TNM-7. The study was approved by the IKNL privacy review board and performed in accordance with the regulations of the Central Committee on Research involving Human Subjects. The IKNL collects data on all cancer patients diagnosed in the Netherlands, based on notification of newly diagnosed malignancies by PALGA and hospital discharge diagnoses. The date of diagnosis was recorded as the date of retrieval of cytology specimens or tissue as mentioned in the pathology report that first confirmed the diagnosis of cancer. Information on demographics, diagnosis, staging and treatment was extracted routinely from the medical records by specially trained IKNL personnel. Clinical and postsurgical stage information was recorded according to the TNM-7. Information on survival status in the IKNL database is updated annually by using a computerized link with the national civil registry. Of the 36,321 patients registered with NSCLC in the Netherlands during the 4-year period 2010 and 2013, a total of 1380 (3.8%) had a diagnosis of cT3N0M0, and of these, 809 (2.2%) were classified as pT3N0M0 disease. The records of these 809 patients with pT3N0M0 disease were matched to the PALGA database to obtain detailed information on the T3 descriptors. Matching was successful in 797 (98%) of the records, with one or multiple reports per patient. A total of 2179 pathology reports were retrieved from the PALGA database, with a range of one to 10 reports per patient (an average 2.7 reports per patient). The data in each report consisted of case identification number, sex, date of birth, date of diagnosis, type of material (cytology or histology) and the integral text of the conclusion of the pathology report, but not the text referring to either the gross or microscopical section reports. The detailed T3 descriptors were identified and coded after review of the reports by one investigator (H.B.). Records were excluded from analysis, if the T3-status could not be confirmed on basis of the conclusion text of the report (n=36) or when the report on the surgical specimen was unavailable (n=28). Other exclusion criteria are shown in the consort flow diagram (Fig. 1), leaving a final study database of 683 eligible patients.
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