Editorial Comment on: Induction and Maintenance Adjuvant Mitomycin C Topical Therapy for Upper Tract Urothelial Carcinoma: Tolerability and Intermediate Term Outcomes by Metcalfe et al.

Upper tract urothelial tumors (UTUC) are relatively uncommon tumors that pose dilemma with their diagnosis and endourologic management. ¹ Although nephroureterectomy is the gold standard treatment, endourologic management with tumor ablation has gained popularity either in well-counseled patients making this informed decision or in imperative indications, such as solitary kidney, bilateral tumors, and renal insufficiency. ^2,3

Ureteroscopy and ablation of UTUC have been increasing over the recent years, as endourologic training, technique, and tools get better. However, for an aggressive disease, outcomes must reflect control of recurrence and progression, which can be achieved through adjuvant topical treatment, such as mitomycin C (MMC). ^4,5 Although MMC is well established in realms of bladder cancer, its use in UTUC is still somewhat limited with only few series reported worldwide. ⁵ The authors present a retrospective series of topical use of MMC either through a nephrostomy or ureteral catheter as a protocol-based instillation with rigorous follow-up. ⁶

In their series of 27 patients (28 renal units), the authors report on the safety, efficacy, and tolerability of adjuvant MMC after complete endoscopic control of UTUC with a median follow-up of 19 months (7–92 months). ⁶ The authors used a 10F nephrostomy tube (n = 9) or a 5F ureteral catheter (n = 19) with a protocol-based MMC instillation as a six weekly induction with a maintenance schedule followed by a rigorous follow-up. Although the results show a recurrence rate of 39%, these compare favorably with the previously reported endoscopic ablative series, which shows recurrences of up to 90%. Four patients were shown to have ureteral stricture that seems to be a recognized complication of this treatment and symptomatic, or imaging follow-up is recommended for early identification.

MMC instillation is now well established for bladder tumors. ⁷ Although this study has used MMC mainly for low-grade tumors, the authors excluded patients with carcinoma in situ and Bacillus Calmette–Guérin treatments. Furthermore, although 86% patients completed the six induction doses, only 7% patients completed the full maintenance dose. Nevertheless, this paves a way for a protocol-based treatment with adjuvant MMC for other endourologists treating these patients. Their recurrence-free survival of 62% at 3 years represents a medium term favorable result, especially in low-grade tumors.

A lack of prospective studies given the rarity of endoscopic management of UTUC, a new prospective single-arm multicentric trial has started looking at the efficacy and safety of chemoablative and adjuvant treatment of UTUC with MitoGel™. ⁸ It seems that although nephroureterectomy still remains the gold standard for UTUC for now, endoscopic management in carefully selected patients will have a better recurrence-free survival using protocol-based adjuvant MMC instillation as shown by the authors in this series.