Limited predictive impact of tumor size dynamics on further tumor shrinkage after 4 cycles of first-line chemotherapy in patients with advanced urothelial carcinoma

Abstract

Purpose: To investigate the correlation between tumor size changes during the initial 4 cycles of first-line chemotherapy and tumor shrinkage following 2 additional cycles of chemotherapy in patients with advanced urothelial carcinoma (aUC) who experienced disease control after initial chemotherapy.

Methods: We retrospectively reviewed 128 patients with aUC who received first-line chemotherapy. We analyzed 51 patients with disease control (stable disease or better) at the end of the fourth cycle. Of these, 47 patients received 1 to 2 additional cycles of chemotherapy, whereas the remaining patients underwent observation. For patients who received additional chemotherapy, the change in tumor size after additional chemotherapy (cycles 5-6) was defined as "no shrinkage" (tumor growth), "minor shrinkage" (no tumor growth or ≤10% reduction in tumor size), or "shrinkage" (>10% reduction in tumor size). Then, we investigated the relationship between the rate of tumor size change during the initial 4 cycles and that after additional chemotherapy.

Results: Of the patients who received additional chemotherapy, the change in tumor size was categorized as no shrinkage in 21 patients (44.7%), minor shrinkage in 18 patients (38.3%), and shrinkage in 8 patients (17%). Regarding predictors of tumor shrinkage after additional chemotherapy, the rate of tumor size change between the cycles 3 and 4 (area under the receiver operating characteristics curve = 0.642) was correlated with the trend of the tumor shrinkage (P = 0.009) and the likelihood of beneficial tumor shrinkage after additional chemotherapy (minor shrinkage + shrinkage; P = 0.02). However, the change in tumor size between cycles 1 and 2, cycles 1 and 4, or cycles 3 and 4 was not satisfactorily predictive of further tumor shrinkage because of substantial overlaps of the tumor size changes.

Conclusions: Only a small subset of patients would have substantial tumor shrinkage by additional cycles after successful induction of 4 cycle chemotherapy. Tumor size dynamics during the initial 4 cycles of chemotherapy displayed limited ability to predict the subset of patients with further tumor shrinkage after additional chemotherapy. Therefore, it might be better to consider switch maintenance immunotherapy for patients who experience disease control after the fourth cycle of first-line chemotherapy.

Keywords: Avelumab; Chemotherapy; Immunotherapy; Switch maintenance; Urothelial carcinoma.