Aims The role of PD-1 (programmed cell death 1) expression on the clinical outcome of upper tract urothelial carcinoma has not yet been elucidated in detail. Materials and methods PD-1 expression was immunohistochemically examined in 181 upper tract urothelial carcinoma patients who underwent radical nephroureterectomy. A part of PD-1 protein expression in the tumour periphery and tumour nest was evaluated separately. The PD-1-positive cells were counted in the area showing the highest density of PD-1 expression at a magnification of 400×. Results PD-1 staining in the tumour nest was low in 137 (75.7%) and high in 44 (24.3%) patients. PD-1 staining in the tumour periphery was low in 78 (43.1%) and high in 103 (56.9%) patients. The 5 year progression-free survival rates in patients with the high PD-1 expression in the tumour nest and in the tumour periphery were 54.6% and 67.7%, respectively, which were significantly lower than those in their counterparts (79.4%, P < 0.001; 80.0%, P = 0.04). The 5 year cancer-specific survival rates in patients with the high PD-1 expression in the tumour nest and the tumour periphery were 69.1% and 75.7%, respectively, which were significantly lower than those in their counterparts (84.7%, P = 0.007; 87.8%, P = 0.01). A multivariate Cox regression analysis identified the high PD-1 expression in the tumour nest (hazard ratio 3.07, P < 0.001; hazard ratio 2.44, P = 0.011) and positive lymphovascular invasion (hazard ratio 4.86, P < 0.001; hazard ratio 4.03, P < 0.001) as independent predictors of disease progression and of cancer death, respectively. Conclusions PD-1 positivity in the tumour nest could be a strong predictor for a worse clinical outcome and may be a useful indicator for selecting appropriate candidates for adjuvant therapy such as chemotherapy in upper tract urothelial carcinoma patients treated with radical nephroureterectomy.
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