Lateral Pelvic Node Metastasis in Locally Advanced Rectal Cancer: Are We Exaggerating or Ignoring?

Abstract

Although the importance of the lateral pelvic node (LPN) in rectal cancer has been described for more than a century, treatments remain in parallel with surgical resection in the East, especially in Japan, whereas neoadjuvant concurrent chemoradiation (nCCRT) is preferred in the West. A recent randomized clinical trial (JCOG0212) in Japan demonstrated the efficacy of LPN dissection (LPND) with total mesorectal excision (TME), which had a lower local recurrence rate (7%) compared with TME alone (13%). However, this strategy may be hardly accepted by Western surgeons since nCCRT is ignored in most advanced rectal cancers. Moreover, the rate of metastatic LPN was 7.4% in the LPND group, indicating that the majority of patients underwent potentially unnecessary LPND. On the other hand, there is ample evidence that nCCRT and TME are insufficient to irradicate metastatic LPNs when LPND is ignored; rather, they cause a considerable incidence of local recurrence, especially in the lateral pelvic wall. The study by Hida et al. in this issue of Annals of Surgical Oncology, through careful review of pelvic magnetic resonance imaging in a large series of Japanese rectal cancer patients, highlighted the prognostic impact of LPND compared with nCCRT alone on improved 5-year estimated overall survival (81.9% vs. 67.3%) and relapsefree survival (69.4% vs. 51.6%) in patients with enlarged LPNs (5–10 mm). In addition, LPND more prominently enhanced relapse-free survival in the subgroup with neoadjuvant treatment than in the TME-alone group (75.2% vs. 33.3%). These results are similar to those of a previous collaborative pooled analysis by the Lateral Node Study Consortium, in which most of the prognostic parameters, such as 5-year distant recurrence (13.5% vs. 30.8%), cancer-specific survival (94.1% vs. 79.4%), local recurrence (5.7% vs 25.7%), and, in particular, lateral pelvic recurrence (5.7% vs. 19.5%), were significantly better with LPND than with TME alone in rectal cancer patients with enlarged LPNs ([7 mm), even after nCCRT. Taking together the lessons from the literature reported on both sides of the world, it is high time to merge these two important treatment modalities in order to provide better clinical outcomes by ‘selective’ LPND with a combination of nCCRT for patients with highly suspicious metastatic LPNs. Therefore, the selection of high-risk patients with metastatic LPN is of paramount importance. As shown in the study by Hida et al., a 5-mm short-axis diameter may be a simple cut-off for the indication of LPND, although the shape, consistency, and responsiveness of LPNs to nCCRT were also taken into consideration. Unfortunately, the investigators applied this size criterion to non-treated LPNs in the surgery (TME ? LPND) group mixed with post-treated LPNs in the neoadjuvant ? surgery group, which might have biased the results. A practical reason why LPND failed to account for the treatment of suspicious metastatic LPNs in the West may be its unfamiliarity and the fear of a higher rate of complications. Indeed, Hida et al. showed a significantly longer operation time, a larger amount of blood loss, and a higher rate of grade 2–3 complications in the LPND group (44.5%) than in the TME-alone group (33.2%). However, Society of Surgical Oncology 2021