Dear Editor

We read with great interest the article by Llod et al. who reported the perioperative outcomes of 28 robotic vs. 72 open retroperitoneal lymph node dissections (RPLND), done by a single surgeon. They also performed a sub-cohort analysis on patients in the robotic group (n = 21) and matched open group (n = 18) who had previous chemotherapy. They found that robotic RPLND is associated with improved peri-operative outcomes, including blood loss, operative time, and length of stay with no difference in complication rates compared to the matched cohort of open RPLND. These improved perioperative outcomes were also seen in the post-chemotherapy setting.

We applaud the authors’ effort to perform this study. However, there are some points in the paper that would worth highlighting:

  1. (1)

    The number in each group is small and makes it “weak powered” for any interpretation. Such an effort might have been more meaningful through larger sample size/multi-institutional study.

  2. (2)

    There is a considerable selection bias, including learning curve, type of cases, dissection template, and surgical approach. Given such biases in this study, comparing these two approaches is like comparing apples and oranges.

  3. (3)

    It seems that for right sided tumor with evident metastasis in inter-aortocaval area (pre- and post-chemotherapy), a modified template RPLND is performed, while the literature including guideline is more in favor of bilateral template RPLND in these cases [1].

  4. (4)

    An ejaculation rate (or possibly retrograde ejaculation) is different from most of body of literature [2, 3]. The authors reported that 30/72 open RPLND vs. 0/28 robotic RPLND had an ejaculation. Although higher percent of non-nerve sparing is anticipated in post-chemotherapy setting, dissociation with robotic arm data is uncertain.

  5. (5)

    The outcomes of interest, such as operative time in the robotic group (150 min) or length of stay in open approach (5 days), are not compatible with the experienced high-volume centers [4, 5]. With extensive experience on both robotic and open surgery in metastatic testicular cancer, we believe that operative time (given the whole set-up) might be longer in the robotic approach. Given lymph node yield, operative time, and more comprehensive surgery (bilateral template) proposed for open cases in this series, it is almost impractical to follow the conclusions of this study.

In conclusion, we acknowledge that there is a lack of high-level evidence in the urology literature regarding the outcomes of robotic post-chemotherapy RPLND. Larger sample size and/or multi-institutional studies with longer follow-ups are needed to delineate the perioperative as well as long-term outcomes of this approach.