Initial experience with magnetic resonance imaging-guided selective lateral pelvic lymph node dissection in the era of total neoadjuvant therapy: a single-centre descriptive cohort and technical review

초록

Background: Lateral pelvic lymph nodes (LPLNs) are an important reservoir of locoregional failure in low rectal cancer. Total neoadjuvant therapy (TNT) improves tumour response and facilitates organ preservation, but the optimal management of radiologically abnormal LPLNs in TNT-treated Western populations remains uncertain. We report our initial experience tracking LPLN response during TNT and provide a contemporary technical review of selective lateral pelvic lymph node dissection (LPLND). Methods: We undertook a retrospective descriptive review of all patients with rectal adenocarcinoma treated with TNT at a single Australian tertiary centre between January 2020 and August 2023. Demographics, LPLN size on magnetic resonance imaging (MRI) before and after TNT, operative details, histopathology and oncologic follow-up were collected, and an independent radiologist validated LPLN measurements. For descriptive tracking, baseline LPLNs measuring >= 5 mm in short-axis diameter were recorded as radiologically abnormal (not as an indication threshold). In parallel, we performed a narrative technical review of open, laparoscopic, robotic, extraperitoneal and transanal approaches to LPLND, with emphasis on selective LPLND in TNT-treated patients. Results: Thirty-one patients completed TNT and were included; nine (29.0%) had radiologically abnormal LPLNs (short-axis diameter >= 5 mm) at baseline. After TNT, all enlarged nodes decreased in size: four resolved completely, three regressed to <5 mm and two remained >= 5 mm. Selective LPLND was performed in one patient with a persistent high-risk node, which contained metastatic disease. During currently available follow-up to 22 March 2026, no confirmed lateral pelvic recurrences were observed, although most patients did not undergo LPLND and pathological confirmation of nodal sterilisation was therefore unavailable. Distant recurrences occurred in a minority of patients. Conclusions: In our initial TNT-era experience, radiologically enlarged LPLNs commonly regressed on restaging MRI, and selective LPLND was required infrequently but can reveal residual metastatic disease in persistent high-risk nodes. These data are descriptive and hypothesis-generating and should be interpreted as an early implementation report rather than practice-changing evidence. Prospective multicentre studies with longer follow-up are needed to define MRI-based selection criteria and quantify functional and oncologic outcomes of selective LPLND in TNT-treated populations.

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