Anatomical location of metastatic lymph nodes in anal carcinoma

Abstract

Anatomical locations of lymph node metastasis in the diagnosis of anal carcinoma Lena Tallberg, Sahlgrenska Academy, University of Gothenburg, Sweden 2018 Background: Squamous Cell Carcinoma of the Anal Canal (SCCAC) is a rare malignant disease, with an increasing incidence during the past decades. Standard regimen of treatment is chemoradiotherapy. During the past decade, Positron emission tomography–computed tomography (PET/CT) has been used more frequently for staging and therapy planning. The radiotherapy techniques of today are more conformal. This puts greater demand on the clinical target volume (CVT)- delineation, to prevent irradiation to healthy tissue and to minimize the risk of leaving micro metastases untreated. Aim: The aim is to map the anatomical localization of regional lymph node metastases in anal cancer, in particular around iliaca externa, compare it with the literature and analyse whether today´s radiotherapy recommendations can be optimized. Method: Patients listed under the diagnose code C21.X in the radiation therapy register during 2010 to 2017 were eligible for inclusion. Demographics were collected from the patient register Melior. The PET/CT lymph nodes were assessed by the nuclear imaging specialist. All data were collected depersonalized in a spreadsheet. The code key were kept separated and in a secure area. Result: Out of a cohort containing 212 patients registered as C.21.X in the year 2010-2017, 166 patients with a verified anal cancer diagnosis and who had undergone a PET/CT were studied regarding anatomical locations of pelvic lymph metastasis. 48.9% of the 166 patients had positive lymph nodes at the time of diagnosis. 18.0% had positive mesorectal lymph nodes, 9.6% presacral lymph nodes, 32.5% inguinal lymph nodes, 7.2% lymph nodes around iliaca interna and 7.2% lymph nodes around iliaca externa. One patient with a <2 cm primary tumour had positive lymph nodes at the time for diagnosis. Furthermore, another patients with <2 cm primary tumour at time for diagnosis later developed a recurrence. No patients had positive iliacal lymph nodes at the time for recurrence. Conclusion: The results suggest that adjuvant pelvic lymph node irradiated volumes may be 3 decreased in small tumours, and potentially decrease morbidity through more restrictive radiotherapy in SCCAC. When comparing the results with the literature, the rate of LNP was seen to be higher than studies using magnetic resonance imaging (MRI) and computed tomography (CT) but was consistent with studies using PET/CT.