The ablative effect of mitomycin reverse thermal gel: Expanding the role for nephron preservation therapy in low grade upper tract urothelial carcinoma

Purpose: Assess the real-world ablative effect of mitomycin reverse thermal gel for low-grade upper tract urothelial carcinoma (UTUC) in patients who undergo biopsy only or partial ablation and evaluate utility of complete ablation prior to UGN-101. Material and Methods: We retrospectively reviewed low-grade UTUC patients treated with UGN-101 from 15 high-volume centers. Patients were categorized based on initial endoscopic ablation (biopsy only, partial ablation, or complete ablation) and by size of remaining tumor (complete ablation, <1cm, 1–3cm, or >3cm) prior to UGN-101. The primary outcome was rendered disease free (RDF) rate at first post-UGN-101 ureteroscopy (URS), defined as complete response or partial response with minimal mechanical ablation to endoscopically clear the upper tract of visible disease. Results: One hundred and sixteen patients were included for analysis after excluding those with high-grade disease. At first post-UGN-101 URS, there were no differences in RDF rates between those who at initial URS (pre-UGN-101) had complete ablation (RDF 77.0%), partial ablation (RDF 55.9%) or biopsy only (RDF 66.7%) (P = 0.14). Similarly, a complimentary analysis focusing on tumor size (completely ablated, <1cm, 1–3cm or >3cm) prior to UGN-101 induction did not demonstrate significant differences in RDF rates (P = 0.17). Conclusion: The results of the early real-world experience suggest that UGN-101 may play a role in initial chemo-ablative cytoreduction of larger volume low-grade tumors that may not initially appear to be amenable to renal preservation. Further studies will help to better quantify the chemo-ablative effect and to identify clinical factors for patient selection.