309 Summary complete response was associated with an essentially better favorable prognosis, namely a 70% 5-year overall survival versus 20% (p=0.001). Patients with a nearcomplete response (defined as less than 10% vital tumor residue) also had significantly better survival than patients with more than 10% vital tumor residue (65% 5-year overall survival versus 18%; p<0.001). This threshold of less than 10% vital tumor residue is now referred to as a criterion for “major pathologic response” (MPR). In chapter 3, additional morphological prognostic characteristics of tumors were sought in the same patient group as in chapter 2, namely in 33 patients with residual tumor after neoadjuvant treatment for a sulcus superior tumor. The study examined whether proliferation (with the biomarker MIB1), PD-L1 (a biomarker related to the immune system), and nuclear size after chemoradiation compared to pre-treatment measurements are related to prognosis. This study showed an increase in tumor nuclear size after chemoradiotherapy, but without prognostic significance. Importantly, low MIB-1 expression was associated with improved survival and disease-free survival, while negative PD-L1 expression also predicted better survival. Further research may be useful to see how these findings can be applied in larger and prospectively followed patient groups in daily practice. The TNM system classifies tumors based on their characteristics, usually the tumor diameter (T), whether there are lymph node metastases (“Node”, N), and whether there are metastases via the bloodstream (metastases, M). The transition from TNM version 7 to version 8 involves a shift of some T descriptors to a different category based on follow-up data from a large international patient group. Chapter 4 presents the results of a national study on T3N0 NSCLC, which was conducted in preparation for Chapter 16, which includes various tumor categories, including those with parietal pleural invasion or a diameter greater than 7 cm. The study in Chapter 4 had two objectives: to assess the validity of this shift in the Dutch population and to investigate whether the inclusion of additional morphological factors could improve staging accuracy. In the group of 683 patients, the 3- and 5-year overall survival (OS) percentages for the subgroup with a tumor diameter greater than 7 cm were 59.9% and 47.2%, respectively. This is comparable to the percentages for 3- and 5-year survival of the subgroup with pleural invasion (50.4% and 45.3%), a group that remained in the T3 category. These findings do not support the relocation of the group with a tumor diameter greater than 7 cm to the pT4 category in the 8th edition of the TNM classification, as is now the case. A newly defined group of patients with 2 or more T characteristics was found, mainly greater than 7 cm in combination with pleural invasion. This group showed worse 3- and 5-year OS percentages (37.5% and 28.7%, respectively), which were comparable to the outcomes for TNM 8th edition stage IIIB and pT4 cases. For the subtype with two or more nodules, the 3- and 5-year OS percentages were 70.6% and 62.8%, respectively, with patients with adenocarcinoma having a significantly better OS than patients with squamous cell carcinoma: a 5-year OS percentage of 65.1% versus 47.2% (p <0.001). This suggests that the prognosis for the A
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