Tumour infiltrating lymphocytes as an independent prognostic factor in transitional cell bladder cancer

The prognostic value of tumour infiltrating lymphocytes (TIL) was assessed in a cohort of 514 patients with a transitional cell bladder cancer (TCC) during a follow up period of over 9 years. The density of TIL were positively correlated to WHO grade (P < 0.0001), non-papillary growth architecture (P < 0.0001), morphometric nuclear factors (P < 0.007) and volume corrected mitotic index (M/V index) (P < 0.0001). Dense TIL predicted progression in Ta-T1 tumours (P < 0.0006) whereas in a multivariate analysis they had no independent predictive value. Dense TIL were related to short recurrence-free survival in Ta-T1 tumours in a univariate analysis (P = 0.06) as well as in a multivariate analysis (P = 0.005). Dense TIL predicted unfavourable prognosis in the entire cohort (P = 0.0316) and in papillary tumours (P = 0.062) whereas in nodular tumours TIL were a sign of good prognosis (P = 0.0141). Also in T3-T4 tumours TIL were related to less aggressive behaviour of TCC (P = 0.0259). In a multivariate analysis including clinical stage (T-category), WHO grade, papillary status, six morphometric nuclear factors and M/V index dense TIL were a highly significant indicator of a favourable prognosis (P = 0.007). Particularly TIL categorized rapidly proliferating TCC into prognostic groups (P = 0.001). The results show that TIL are a sign of efficient host defence mechanisms in TCC and TIL predict a favourable prognosis in invasive TCC.