Yang Z, et al. - A total of 162 patients were randomly allocated to either the ribonucleotide reductase subunit M1 (RRM1)-known group or the unknown group by the researchers in order to clarify the value of RRM1 expression in prognosticating progression-free survival in non-muscle-invasive bladder cancer (NMIBC) patients treated with intravesical gemcitabine chemotherapy. Cancer tissues from 81 patients to assess the mRNA expression of RRM1 were collected. In 21% of patients, RRM1 expression was high. The RRM1 mRNA level was not associated with sex, age, weight, performance status, or China Urological Association/European Association of Urology risk. For patients with low RRM1 expression vs patients with high and unknown RRM1 expression, progression-free survival (PFS) was significantly prolonged. Moreover, the 1- and 2-year relapse rates also varied according to the RRM1 expression level. The 1-year and 2-year relapse rates were 0, 17.7 and 6.2%, and 3.1, 29.4, and 11.1 % for RRM1-low, RRM1-high, and RRM1-unknown individuals, respectively. Therefore, in NMIBC patients treated with intravesical gemcitabine monotherapy, low RRM1 expression was correlated with more prolonged PFS and lower 1-year/2-year relapse rates, regardless of the requirement for further validation with large sample sizes and acknowledging more mixed factors and biases.