Tumour response to neoadjuvant chemoradiation within lateral pelvic nodes: another step towards precision surgery

Abstract

Lateral lymph-node dissection (LLND) in extraperitoneal rectal cancer has been neglected for a long time in western countries. In addition to being a technically challenging procedure, the high risk of perioperative blood loss and negative effects on urinary and sexual function have contributed to the lack of widespread implementation of LLND in clinical practice outside Japan and Korea [1,2]. Moreover, with the establishment of multimodal treatment in the management of locally advanced rectal cancer, it has been suggested that patients undergoing preoperative radiation with or without chemotherapy would not require LLND as radiation could potentially sterilize lateral pelvic nodes included in the radiation therapy field [3].Recently, LLND has attracted significant attention for several reasons. First, the results of a prospective randomized trial in Japan that failed to demonstrate non-inferiority of total mesorectal excision (TME) when compared to TME + LLND in patients with no preoperative evidence of lateral node metastases was quite disturbing [4]. No radiotherapy was used in this trial. The outcomes revealed a higher rate of local recurrence among patients undergoing TME alone. The same trial also demonstrated no differences in male sexual function after LLND when compared to TME alone [5]. Finally, despite the fact that LLND was associated with increased intraoperative bleeding, an elegant case-matched control study in Japan suggested that a minimally invasive approach could potentially solve this particular issue and minimal intraoperative bleeding was reported using the laparoscopic approach [6].As multimodality treatment of rectal cancer is now mainstreaming in Japan as well, a more selective approach to LLND has been the focus of recent publications. Specific Japanese and Korean centers are suggesting that only in the presence of positive lymph nodes at baseline, should patients undergo "selective" LLND after neoadjuvant chemoradiotherapy (nCRT) [7]. In fact, their own data suggest that nCRT is able to sterilize nearly 50% of lymph nodes. This means that only 50% of these patients would still harbor lateral node metastases after nCRT and would ultimately benefit from LLND. One patient out of two would not [7,8].In the present edition of Techniques in Coloproctology, Ishihara et al. are taking a step forward in the selective approach for LLND in rectal cancer. With the use of reassessment of tumor response using computed tomography/positron emission tomography (CT/PET) scanning they provide an interesting tool to predict the presence of residual lateral node metastases after nCRT. Using size and metabolic estimate [maximum standardized uptake value (SUV max )] cut-offs after nCRT, they were able to predict with high accuracy the presence of lateral node metastasis. This strategy allowed the authors to correctly identify patients that could benefit the most from LLND.However, prior to implementation of these results in clinical practice, rectal cancer surgeons should consider the following points: First...