31 Outcomes of resected SST after CRT 10% tumour regression. We found more cytonuclear atypia in cases with more necrosis than fibrosis, in line with Yamane et al29. The pCR or minimal residual disease rate of 50% (23/46 cases), is broadly in keeping with that reported by others (Table 6), however there is some variation between studies. For example, Rusch et al26 described a series of 88 patients and found up to 69% pCR or minimal residual tumour. One possible explanation for the differences might be variation in the how the pathological assessment was made (which is often incompletely described) or in histopathologic definition of response. Table 6. Selected series of patients with non-small cell lung cancer and histopathologic evaluation after CRT Reference No. evaluable cases No. patients with CRT (%) Mean radiation dose No. of patients with pCR (%) No. of patients with pCR or minimala residual tumour cells This article 46 46 (100%) 53 Gy 20 (43%) 23 (50%) Pourel25 71b 71 (100%) 45 Gy n.m. 28 (39.4%) Rusch26 88 88 (100%) 45 Gy 32 (36%) 61 (69%) Junker27 40 40 (100%) 45 Gy 7 (17%) 27 (67%) Liu28 30 20 (66%) 50 Gy 5 (25%) 13 (65%) Fischer38 44 44 (100%) 45 Gy 13 (30%) 28 (64%) CRT chemo-radiotherapy, pCR pathologic complete response, n.m. not mentioned a minimal residual cells is variably defined in different studies. For example, in this study and the report by Fischer et al it was <10% b107 pts in the study, 105 completed CRT, 72 underwent surgery, 71 were pathologically evaluable The results add to the growing body of evidence indicating that a complete or nearcomplete pathologic response is associated with a more favourable prognosis in patients with SST. This is in line with Yamane et al. who report that a smaller area of residual tumour is associated with a better prognosis29. Significantly more pCR was found in cases with a partial imaging response compared to cases with stable disease. Although the RECIST criteria were not designed to compare radiological tumour diameters with diameters measured on pathologic resection specimen, we found significantly more cases with ‘partial response’ when we compared the diameters on pre-treatment imaging with those in the resection specimens. The latter also tended to be smaller compared to post-treatment imaging diameters. These data suggest that pCR is more likely to be found in cases with larger diameters with subsequent significant regression on combined modality treatment, than in cases that were stable on imaging despite a smaller initial size. Junker et al27 describe a 3-grade regression scoring system for patients receiving induction therapy i.e. grade I, no or slight regression; IIA, marked but incomplete 2
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