Inguinal Lymph Nodes Management In Squamous Cell Carcinoma Of The Anal Canal

Current issues in the management of clinically negative inguinal lymph nodes in squamous cell carcinoma of the anal canal. Quality of the available evidence. Background The first line of management of squamous cell carcinoma (SCC) of the anal canal is chemo-radiation. The radiation field includes, in addition to the anal region and the perirectal nodes, the iliac and both inguinal triangles to target the inguinal nodes. More recently a selective approach has been investigated in patients with non-palpable inguinal nodes utilizing sentinel node biopsy and PET scan. Methods Medline was searched using the keywords, squamous cell carcinoma, anal canal, inguinal lymph nodes, sentinel node and radiotherapy. Relevant articles were reviewed with regard to the management of inguinal nodes in SCC of the anal canal. Results: Currently the management of clinically normal inguinal nodes in SCC of the anal canal is prophylactic radiation of both inguinal areas. Clinically involved nodes are included in the radiation field plus a boost of radiation to the groin that harbor involved nodes. The radiation is refined recently by intensity modulation radiotherapy (IMR) to involve the diseased area and minimize radiation exposure of normal adjacent tissues. Alternatively, more recently, a selective approach with utilization of sentinel node biopsy and radiation to microscopically involved nodal areas has been described. Conclusion: The treatment of clinically normal inguinal nodes is currently by prophylactic radiation of both inguinal regions. It is possible that in the future radiation of clinically normal inguinal may become more selective with an increasing reliance on sentinel node biopsy. Further studies are needed in this field to assess the efficacy of this approach. Background Although Squamous cell carcinoma (SCC) of the anal canal is an uncommon disease it is the most common malignant tumor of the anal canal accounting for 90% of malignant tumors at this site. Survival is determined essentially by two factors; the size of the tumor and lymph node spread. Patients with no clinical evidence of nodal disease have a ten-year survival of 73% compared with 53% in those with nodal disease.1 Historically the treatment of SCC of the anal canal was abdominoperineal resection; this involves wide dissection of the ischiorectal fossa with clearance of pararectal lymph nodes with en bloc excision of the posterior vaginal wall in women 2. The current management of SCC of the anal canal is chemoradiotherapy, which includes infusion of 5-flourouracil with or without mitomycin and radiation fields that include the primary tumor and the pelvic and inguinal lymph nodes.3, 4, 5, Surgery is reserved for patients who have an incomplete response, residual disease and those with later disease recurrence. The lymphatic drainage of tumors of the anal canal is bidirectional and depends on the tumor location in relation to the dentate line. Above the dentate line most of the lymph drains in a cephalad direction along the inferior rectal artery to the origin of the inferior mesenteric artery, also along the territory of the middle rectal artery to the iliac nodes. Below the dentate line it drains to the inguinal nodes along the femoral artery. Hence the lymphatic drainage is to the ipsilateral inguinal lymph nodes. The probability of nodal spread is relative to the tumor size (T stage). 1 When the primary tumor is clearly located laterally, the inguinal metastasis nearly always is homolateral to the primary tumor. Midline tumors and locally advanced lesions usually show bilateral inguinal and pararectal lymph node involvement. In the Lyon series bilateral involvement was seen only when the primary tumor involved the medial part of the anal canal. 6 Overall, inguinal nodal involvement occurs in 10-25% of patients 7, 8,9, 10. Using bipedal lymphangiography in a group of patients with anal cancer Davey et al demonstrated metastasis to external iliac lymph nodes in 7 out of 28 patients (25%).11 CT detected disease in the external iliac nodes in only one of these patients. WebmedCentral > Review articles Page 2 of 9 WMC001565 Downloaded from http://www.webmedcentral.com on 24-Dec-2011, 07:35:37 AM Lymph node involvement is related to the T stage of the tumor with nodal metastases seen in 0-10% of T1 and 2 lesions and 4050% of T3 and 4 disease (table 1).12, 11 At the time of diagnosis local tumor extent is T1: 8.5%; T2: 51.1%; T3: 30.4%; T4: 10%.1 Pelvic lymph node involvement correlates with increasing risk of pelvic relapse and residual disease after definitive radio-chemotherapy. Pelvic nodes are routinely targeted within the radiation field of the primary tumor and therefore their involvement or otherwise are unlikely at this stage to change the approach of treatment. However this is not the case for inguinal lymph nodes. Clinical examination and CT scan are not sensitive for detecting inguinal node metastases due to the fact that the size of the lymph node does not accurately predict the likelihood of metastatic disease and 44% of involved nodes are less than 5 mm in maximal diameter.12 Currently the treatment of clinically negative inguinal nodes is prophylactic radiation given by inclusion of both inguinal regions in the radiation field with a radiation boost if the nodes are clinically involved. More recently a selective approach has been explored utilizing staging information obtained from sentinel node biopsy and PET scan. We conducted this review to assess the current strategies for dealing with treatment of clinically negative inguinal lymph nodes.