Anal Cancer
Anal cancer accounts for only 4 % of all cancers of the lower alimentary tract. However, the incidence is rising—possibly due to the higher incidence of persons engaging in anal-receptive intercourse. Chemoradiotherapy has become the standard treatment fo
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Key Concepts • Chemoradiotherapy (CRT) is the primary treatment for patient with anal squamous cell carcinoma (mitomycin + 5-FU + radiotherapy). The dosage of radiotherapy varies based on the size of the tumor and presence of lymph node involvement. • Surgery (local excision) can be used to remove some small squamous cell carcinomas (usually measuring 90 % and a specificity of 80 %. PET/CT has been shown to alter the staging of anal carcinoma in approximately 20 % of cases, and treatment intent in approximately 3–5 %. The main impact of PET/CT on therapy stems from its superiority in detecting involved pelvic or inguinal nodes, prompting the radiation oncologist to include these in the RT field [18, 19, 20]. PET/ CT has also impacted posttreatment management in 18 % of anal cancer patients (Fig. 21-8). It may confirm persistence of disease or local recurrence, and influence decision making regarding the use of chemotherapy in patients with metastatic disease [3, 21]. The high negative predictive value of PET-CT may dictate avoidance of unnecessary biopsy after chemoradiotherapy.
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FIGURE 21-8. Anal cancer: pretreatment SUV = 18.1.
T. Samdani and G.M. Nash
cers require higher doses of radiation. The database of the RTOG 9811 trial suggests that size >5 cm is a poor prognostic factor [29]. Doses in the range of 30 Gy, with concurrent mitomycin C and 5-FU, have been shown to control small tumors (CCR rate of 86 %) and subclinical disease effectively. The preliminary results of the ACCORD-03 trial compared 45 Gy in 25 patients plus a 15 Gy boost with a higher dose, but found no benefit in CFS, and higher toxicity, at >59 Gy [30]. Similar results were reported in the RTOG 92-08 trial [31]. Patients with SCAC receive a minimum RT dose of 45 Gy to the primary cancer. The recommended initial dose is 30.6 Gy to the pelvis, anus, perineum, and inguinal nodes. Following initial dose of 30.6 Gy, field of radiation should be reduced from L5–S1 junction to bottom of sacroiliac joints. In patients without nodal metastasis, inguinal nodes are not included in radiation field after 36 Gy. Patients with disease clinically staged as node positive or T3–T4 or with T2 residual disease after 45 Gy should receive an additional boost of 9–14 Gy [28].
Summary of the Initial Work-Up of Anal Cancer 1. In the setting of a T1 tumor, after a thorough physical exam, MRI of the rectum/pelvis or transanal endoscopic ultrasound may be used for additional local staging. In the absence of nodal disease, a CT scan of the chest and abdomen may be used for distant staging. 2. In the setting of a T2–T4 tumor or node-positive anal cancer, PET/CT may be used in addition to MRI or transanal endoscopic ultrasound to screen for distant metastases, to assess response to CRT, and as a tool in subsequent cancer surveillance.
Treatment of Anal Cancer Until three decades ago, abdominoperineal resection (APR) of the rectosigmoid and anus was the preferred surgical procedure for most cancers of the anal canal. This radical operation was performed in order to
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