Is Elective Inguinal or External Iliac Irradiation During Neoadjuvant (Chemo)radiotherapy Necessary for Locally Advanced Lower Rectal Cancer With Anal Sphincter Invasion?

Abstract

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Dentate line invasion as a predictive factor of poor distant relapse-free survival in locally advanced lower rectal cancer with anal sphincter involvement

“…Meanwhile, irradiation of ILNs and ELNs might result in significant and frequent complications because of the larger treatment volume. This study showed that the 5-year failure rate was 4.8% for ILNs and 3.3% for ELNs, which were as low as our previous 3-year failure rates [ 17 ]. In addition, the anatomical mechanism and failure patterns also indicated that ILNs and ELNs might be systemic metastatic stations [ 17 , 43 ].…”

“…These increased distant metastasis sites may be explained by the following anatomical factors. First, the lymphatics below the dentate line mainly drain into the ILNs, and some recent clinical studies have confirmed that patients with DLI have a higher rate ILN failure [ 17 , 28 ]. In addition, the superior rectal vein drains the rectum and anal canal above the dentate line through the inferior mesenteric vein to the portal venous system, and the external hemorrhoid plexus is below the dentate line, which drains by way of the inferior rectal vein to the internal pudendal vein and then into the internal iliac vein and systemic circulation [ 29 ].…”

“…All patients received simultaneous integrated boost intensity-modulated radiation therapy. The definition and delineation of the clinical target volume (CTV) recommendations were in accordance with protocols described in previous reports [ 17 , 21 , 22 ]. A total dose of 50.6 Gy (2.3 Gy/fraction) and 41.8 Gy (1.9 Gy/fraction) both in 22 fractions were prescribed to the planning gross tumor volume and the planning target volume, respectively [ 22 ].…”

“…In our previous study, DLI in LALRC patients was a pre-treatment factor associated with poor 3-year DFS, but not with local recurrence-free survival (LRFS); moreover, distant failure is more common than local recurrence [ 17 ]. In addition, systemic relapses remain a major problem in locally advanced rectal cancer [ 24 ].…”

“…Hamano et al suggested that LALRC patients who have dentate line invasion (DLI) present a higher rate of inguinal lymph node (ILN) metastasis and poorer prognosis than those of patients without DLI [ 16 ]. Our previous results also revealed that DLI in LALRC patients was a pre-treatment factor associated with decreased 3-year disease-free survival (DFS) [ 17 ]. Although the above retrospective studies preliminarily confirmed the prognostic significance of DLI, its impact on local recurrences or distant metastases have seldom been systematically described or considered.…”