30 Chapter 2 2). There were no differences in cases with 10-50% compared to >50% vital tumour cells. A low mitotic count (< 1 per high power field) was associated with a longer diseasefree survival (p=0.02). None of the other associations between histological scores and follow-up status were statistically significant. Figure 2. Kaplan-Meier survival curves showing a significantly better prognosis in patients with less than 10% vital tumor cells in their resection specimen. Discussion This is the largest series reporting a detailed histopathologic evaluation of resected Pancoast tumours after tri-modality therapy. Twenty-three out of 46 patients (50%) with SST showed pathological complete response (n=20) or <10% vital tumour cells (n=3) after CRT. Pathologic complete regression or the presence of <10% vital tumour cells was associated with survival. A low mitotic rate was associated with a longer disease-free survival37. The majority of patients with radiological partial response according to RECIST criteria had a pathologic complete response. There were no statistically significant differences between the patients or outcomes from the two institutes, even though their treatment regimens differed. Tumour regression in the lesions was associated with histologic features of necrosis and/or fibrosis, as well as variable histiocytic reactions such as foam cells and cholesterol crystal-related giant cells. These findings are similar to those of Liu-Jarin et al, who analyzed the histological patterns in 30 surgical resection NSCLC specimens after neo-adjuvant therapy28. In their study, consisting of 15 cT3 tumours, the extent of fibrosis correlated with the radiologic response in patients that showed more than
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