23. Anal Cancer - The GEC-ESTRO Handbook of Brachytherapy

Anal Cancer

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THE GEC ESTROHANDBOOKOF BRACHYTHERAPY | Part II Clinical Practice Version 1 - 01/03/2023

Figure 2: Some examples of clinical appearance of anal canal cancers. Tumours are indicated by the black arrow. Anal canal cancers can present in different forms: as a mass (pictures A and B) or as an ulceration (pictures C and D) of varying size.

For women, a gynaecologic examination should be performed to assess involvement of the genital tract by the anal cancer, as well as screening for a concurrent genital tract cancer. If necessary, sedation should be considered when the physical examination is too painful. Laboratory studies Laboratory studies should include a complete blood cell count, measurement of serum creatinine levels, and liver function studies. For patients with HIV risk factors, a determination of HIV status should be made before initiating therapy. There are no other clinically useful blood tumour markers for anal cancer [10]. Squamous cell carcinoma antigen (SCC) is used by some teams, with no clinical validation from trials. Imaging The two main imaging exams for anal cancers are a CT scan of the pelvis, abdomen and chest and anMRI of the pelvis (figure 4). Complementary to the physical examination of the primary tumour, imaging exams are useful for the evaluation of the liver and regional lymph nodes (perirectal, inguinal, pelvic and para-aortic lymph nodes). They are also essential for disease assessment for external beam radiotherapy (EBRT) and brachytherapy planning. Fluorodeoxyglucose-PET (FDG-PET) imaging is useful in cases of doubtful results after the standard exams, and in further evaluating the extent of the primary tumour and the presence of regional lymph node metastases and distant metastases, as well as in evaluating the response to therapy (figure 5). An FDG-PET scan is recommended for stage III cancers (TxM0 with lymphatic invasion, and T3NxM0), to better ascertain lymphatic and, less commonly, metastatic dissemination [11–13]. An FDG-PET scan should also be considered for T2N0 tumours more than 3-4cm long [9]. Furthermore, the extent of disease the initial FDG-PET (before concurrent radio-chemotherapy) is strongly predictive of

Figure 3: Example of a diagram summarising all the physical findings

prognosis in anal cancer: patients with a large metabolic volume of the primary tumour (>45mL) are at a significantly higher risk of recurrence [14]. Anal and rectal endoscopic ultrasound is an option to complete the overall assessment of the disease, in particular to determine sphincter invasion. Sphincter invasion doesn’t change the tumour status according to the TNM 8th edition (see paragraph below), but in anticipation of brachytherapy, a better knowledge of the extension in depth allows for better planning. Endoscopic ultrasound does not provide any advantage over digital rectal examination in identifying locally recurrent anal cancer and should not be recommended for routine surveillance [15]. Staging Anal cancer should be staged according to the TNM staging system (as described in table 1 and 2) of either the American Joint Committee onCancer (AJCC) or the Union for International Cancer Control (UICC), both classifications being identical. Tumours are classified by their maximum diameter and their invasion of adjacent structures, as determined by the physical examination and any imaging studies. For staging purposes, the regional lymph nodes are the anorectal, perirectal, lateral sacral, internal iliac (hypogastric), and external iliac lymph nodes. All other lymph node groups are considered distant metastases.