Impact of Time to Surgery on Outcome in Wilms Tumor Treated with Preoperative Chemotherapy

SIMPLE SUMMARY: In SIOP, trials and studies for Wilms tumor (WT) start with chemotherapy before the surgical removal of the tumor. The aim of this study is to find out whether the time between the start of preoperative chemotherapy and surgery has an influence on the outcome of WT patients. Therefore, we analyzed a completely German, Austrian, and Swiss cohort of 2561 unilateral WT patients pretreated between 1989 and 2022. This retrospective analysis shows no such influence on the occurrence of relapses and survival in unilateral WTs. However, in bilateral tumors with prolonged pretreatment, to achieve as many nephron-sparing surgeries as possible, preoperative treatment should not exceed 120 days due to an increased risk of relapses. ABSTRACT: (1) Background: Wilms tumor (WT) treated preoperatively is cured in over 90% of cases. However, how long preoperative chemotherapy can be given is unknown. (2) Methods: 2561/3030 patients with WT (age < 18 years) treated between 1989 and 2022 according to SIOP-9/GPOH, SIOP-93-01/GPOH, and SIOP-2001/GPOH are retrospectively analyzed to assess the risk of time to surgery (TTS) for relapse-free survival (RFS) and overall survival (OS). (3) Results: TTS was calculated for all surgeries, with the mean being 39 days (38.5 ± 12.5) for unilateral tumors (UWT) and 70 days (69.9 ± 32.7) for bilateral disease (BWT). Relapse occurred in 347 patients, of which 63 (2.5%) were local, 199 (7.8%) were metastatic, and 85 (3.3%) were combined. Moreover, 184 patients (7.2%) died, 152 (5.9%) due to tumor progression. In UWT, recurrences and mortality are independent of TTS. For BWT without metastases at diagnosis, the incidence of recurrence is less than 18% up to 120 days and increases to 29% after 120 days, and to 60% after 150 days. The risk of relapse (Hazard Ratio) adjusted for age, local stage, and histological risk group increases to 2.87 after 120 days (CI 1.19–7.95, p = 0.022) and to 4.62 after 150 days (CI 1.17–18.26, p = 0.029). In metastatic BWT, no influence of TTS is detected. (4) Conclusions: The length of preoperative chemotherapy has no negative impact on RFS or OS in UWT. In BWT without metastatic disease, surgery should be performed before day 120, as the risk of recurrence increases significantly thereafter.