EAU guidelines verified the minimally invasive and conservative kidney-sparing approach for low-risk UTUC as an alternative treatment for RNU [6]. As EAU and NCCN guidelines suggest, URS treatment for UTUC should be performed in patients with low grade tumors; UTUC in solitary kidney, impaired renal function and bilateral UTUC was also imperatively indicated for KSS in highly selected patients [6, 13].
In a systematic review by Seisen et al. [9], only patients with low-grade and non-invasive UTUC had similar survival after URS management for UTUC versus RNU. However, in our study, only the tumor grade group and tumor size group achieved statistical significance. However, the biopsy stage group was not statistically significant. This difference may imply that both tumor size and tumor grade are more influential factors than biopsy stage in local recurrence-free survival. We surmise that the biopsy stage by URS is not consistent with the actual tumor stage because biopsy cannot precisely grasp the actual depth of tumor invasion. However, tumor size may be indicative of the grade of tumor invasion.
Due to the high prevalence of UTUC in southwestern Taiwan, many patients cannot fit in the low-risk group. In the review by Fiuk et al., they extended the indication for KSS to the following populations: (1) UTUC in solitary kidney, (2) renal insufficiency imposing the threat of hemodialysis if any further renal insult, (3) bilateral UTUC, (4) comorbidities enough to be life-limiting or to incur additional risk with RNU, and (5) low-risk tumors with stringent follow-up [14].
Therefore, we selected patients with imperative indications and analyzed the results after laser ablation of UTUC. In our study, female predominance is noted; it is speculated that female patients were highly exposed to arsenic steam during cooking from the boiling water [15]. However, our statistics showed that men had a higher tendency of recurrence with near statistical significance. Age was statistically significant in the multivariate analysis, but Chromecki et al. suggested that age was not an independent predictor of outcomes of UTUCs [16].
In endoscopic treatment for UTUC, multiple studies showed efficacy and safety [9, 17, 18].
We used the Flexible URS combined with the Thulium laser system for treating renal pelvic UTUC. The statistical results showed no significant difference between the renal pelvic tumor (flexible URS) and ureteral tumor (rigid URS), and may result from advances in current technology that allows us to approach all parts of the renal collecting system.
In the NCCN guidelines, low-grade UC of the renal pelvis treated by endoscopic resection is suggested to be followed by postsurgical intra-ureteral (intra-pelvic) chemotherapy or BCG [13]. In our study, a small number of patients (n = 5) received intra-ureteral (intra-pelvic) chemotherapy. The outcome of local recurrence was not statistically significant. Due to the high risk of acute pyelonephritis after intra-ureteral (intra-pelvic) chemotherapy, we terminated the therapy after administering it to a few patients. Repeat acute pyelonephritis will also induce permanent deterioration of renal function.
The recurrence rate of bilateral UTUC is lower than that of unilateral UTUC, but only 5 patients had bilateral disease; the statistical analysis also showed no significance. The tumor characteristics of these 5 patients were small tumor size and earlier tumor stage (Ta and Tis); thus, the lower rate of recurrence.
We combined two of three tumor characteristics (stage, size, and grade of tumor) for subgroup analyses. In the tumor grade + tumor size group, statistical significance was noted with a p-value = 0.0275 (Fig. 4). We noticed that the subgroup of small tumor size (tumor < 2 cm with low/high grade) still had a lower local recurrence than did large tumors (tumor > 2 cm with low/high grade) (Fig. 4). The subgroup analysis of tumor size + biopsy stage also showed the same pattern as that small tumor size (tumor < 2 cm with Tis/Ta/T1) had a lower local recurrence than did large tumors (tumor > 2 cm with Tis/Ta/T1) (Fig. 5). However, no statistical significance was achieved in the subgroup analysis of tumor grade + biopsy stage (Fig. 6). These results imply that the factor of tumor size was more influential than tumor grade and biopsy stage in the prognosis of local recurrence.
Despite considerable experience treating UTUC by endoscopic management, risks of both understaging and undergrading remain. Up to 25% of UTUC lesions had been missed, and almost 50% of carcinoma in situ lesions were missed [19].
The limitations of our study included: (1) a small number of patients (n = 34), (2) short follow-up duration (mean = 25 months), and (3) retrospective, single-center study design.
Because we excluded 34 patients due to (1) short follow-up duration (less than 6 months), (2) previous history of urinary bladder UC, and (3) concomitant diagnosis of UTUC and bladder UC at the first visit, it resulted in a small number of patients who were included in our study. Also, laser ablation is a novel technique for the management of UTUC in the recent decade and results in a short follow-up duration. We need a longer follow-up duration for an accurate survival estimate.
We shared our experience of laser ablation of UTUC to provide direction to regions or countries that have a high incidence of UTUC, such as southwestern and northeastern Taiwan, the Balkan area, and other Chinese herb-consuming regions.