The findings of this study indicated a significant relationship between the clinical benefit derived from the first-line treatment in patients with metastatic urothelial carcinoma and the clinical benefit derived from the atezolizumab treatment administered to these patients as the second-line treatment. Additionally, it was also determined that the patients who were clinically benefited from the first-line treatment had significantly longer overall survival times calculated by taking the start of the atezolizumab treatment as the baseline. These findings are very important in that they can be utilized as stratification factors in immunotherapy studies to be conducted on bladder cancer patients with disease progression following first-line treatment.
In the Javelin bladder 100 trial, a study of avelumab in patients with locally advanced or metastatic urothelial cancer, it was demonstrated that the patients who had non-progressive advanced urothelial carcinoma following the first-line platinum-based chemotherapy had significantly longer OS times following the administration of avelumab therapy as the maintenance therapy not later than 10 weeks after the completion of the first-line treatment, as compared to the patients that were provided the best supportive care [13]. In parallel to the results of the said trial, administration of avelumab therapy as the maintenance therapy has been accepted as the standard treatment protocol for patients who were clinically benefited from the platinum-based chemotherapy. The Javelin bladder 100 trial also revealed that the patients with advanced urothelial cancer were clinically benefited from the avelumab therapy, irrespective of whether they received cisplatin or carboplatin as the first-line treatment.
In comparison, in this study, from among the patients that received first-line treatment, 87 (83%) patients received second-line treatment in the form of atezolizumab in 3 months time or even before then as a result of disease progression following the first-line treatment, and forty-four percent (44%) of the patients received carboplatin-based chemotherapy. Similar to the findings reported in the Javelin bladder 100 trial, in this study as well, no significant differences were found between the OS and the type of the chemotherapy administered and the period elapsed between the completion of the chemotherapy as the first-line treatment and the initiation of atezolizumab therapy as the second-line treatment.
CBRs of the patients that received cisplatin-based chemotherapy were calculated between 75–80%, nevertheless nearly 50% of the patients who had metastatic urothelial carcinoma were not eligible to receive cisplatin-based chemotherapy [3, 4]. ORRs of the patients that were not eligible to receive cisplatin-based chemotherapy were around 40%, and lower than the ORRs of the patients that were eligible to receive cisplatin-based chemotherapy [14]. Therefore, many patients who have metastatic urothelial cancer do not actually meet the required eligibility criteria to receive avelumab therapy as the maintenance treatment.
In comparison, in this study, CBRs of the patients with metastatic urothelial cancer that received the first-line treatment was calculated as 56.2%. Forty (74.1%) patients, who were determined to have clinically benefited from the first-line treatment, were found to have clinically benefited from the atezolizumab treatment as well. On the other hand, only fourteen (25.9%) patients with a disease progression following the first-line treatment were found to have clinically benefited from the atezolizumab treatment. Therefore, in this study, unlike the Javelin bladder 100 trial, a group of stage IV bladder cancer patients, who were determined not to have clinically benefited from chemotherapy as the first-line treatment, were found to have benefited from the immune checkpoint inhibitors blockade treatment as the second-line treatment.
In the INDUCOMAIN study, it was demonstrated that the stand-alone use of immune checkpoint inhibitors prior to induction chemotherapy is not an adequate strategy, since it was found that the use of said strategy led to more frequent early disease progression [15]. In comparison, in this study, as was the case in the Javelin bladder 100 trial, use of chemotherapy immune checkpoint inhibitors was demonstrated to be a good treatment option for metastatic urothelial carcinoma following the administration of induction chemotherapy [13]. Additionally, initial chemotherapy could potentially induce immunogenic cell death or depletion of suppressive immune cell populations such as myeloid-derived suppressor cells, thereby enhancing the effect of subsequently administered checkpoint inhibitors [16].
There were some limitations to this study. First, it was carried out as a retrospective study. Thus, responses to the treatments had to be determined by the data collector on the basis of the relevant radiographic and clinical data, and the respective analyses did not include a central evaluation carried out by a blinded radiologist according to RECIST criteria. Secondly, there were some potential confounder variables.