Anal canal cancer
Radiation therapy with concurrent chemotherapy is the standard treatment for patients with nonmetastatic squamous cell carcinoma of the anal canal. In the studies that established this approach, high rates of locoregional control have been reported, but the incidence of acute and late toxicity has been significant. Moreover, treatment-related acute toxicity may cause treatment interruptions that are potentially detrimental to locoregional control and colostomy-free survival. Intensity-modulated radiation therapy (IMRT) has recently been instituted as an alternative to conventional two-dimensional (2D) or three-dimensional (3D) conformal radiotherapy. Multiple institutional experiences, as well as a single phase II multi-institution prospective study, have demonstrated improved acute toxicity rates with IMRT, potentially minimizing treatment interruptions and improving treatment outcomes. Pilot studies evaluating IMRT show no reduction in overall or colostomy-free survival versus historical studies. Due to its high precision, the use of IMRT in anal cancer requires thorough understanding of the patterns of spread of anal cancer with thoughtful delineation of target volumes and organs at risk. In this chapter, we highlight the available data on the use of IMRT for anal cancer and summarize established approaches for IMRT planning in this disease.
