Response to letter to the Editor re 'Outcomes of event-free survival in patients with Wilms tumor undergoing preoperative chemotherapy. Analysis of lymph-node yield in a single-center cohort'

We would like to thank you for your interest in our study. This article showed that patients treated according to the SIOP protocol with a lower LNY than suggested presented with acceptable survival outcomes and recurrence rates. As mentioned in the manuscript, we agree that our study has several limitations. First, as it was a single-center study, the conclusions were drawn based on the assessments of one group of surgeons. Second, due to the small size of the cohort no statistical results could be obtained when analyzing outcomes comparing the different histological subtypes, which would have been very useful. Moreover, we were not able to statistically validate an LN threshold value. On the other hand, we would like to clarify that positive margins in Stage III patients were not due to a surgical rupture of the pseudocapsule. These patients presented with viable tumor cells at the resection margin and were histologically defined as Stage III. This point is crucial, as it is independent of the surgeon's skills, which was the reason why it was not analyzed separately. Regarding the laparoscopic approach, LNY was significantly lower in this group with no recurrences so far (follow-up 25 months). Unfortunately, discrepancies between the laparoscopic and the open-surgery group did not allow us to draw any statistical conclusions. As a final consideration, we would like to emphasize that the standardization of LN sampling patterns is crucial to reduce the risk of harboring occult lymph-node metastasis and ameliorate biases. All patients analyzed in this cohort underwent methodic LN sampling as explained in the text. Operating these patients in a standardized fashion encouraged us to publish and share our experience with other colleagues.