ARLINGTON, Va., February 27, 2025 — A new clinical guideline from the American Society for Radiation Oncology (ASTRO) provides guidance on the use of radiation therapy to treat adult patients with primary squamous cell carcinoma (SCC) of the anal canal and anal margin. The guideline, ASTRO's first for anal cancer, is published in Practical Radiation Oncology.
Although anal cancer is relatively rare compared with colon or rectal cancers, incidence and mortality rates have risen steadily over the past two decades, particularly among adults in their 50s. An estimated 10,540 Americans are diagnosed with anal cancer each year, mostly frequently Black men and white women. Overall, women are more than twice as likely as men to develop the disease.
Unlike other gastrointestinal cancers, anal cancer has a lower tendency to metastasize, and most patients are diagnosed with locoregional disease (stages I–III). Treatments for this cancer tend to be effective, and many people diagnosed with the disease can be cured.
The current standard of care for anal cancer involves a combination of radiation therapy and drug therapy that allows patients to avoid the permanent colostomies that previously were common with surgical treatments. This organ-preserving strategy is effective at controlling locoregional disease, but it also is associated with short- and long-term side effects that can impact quality of life. Ongoing research in treatment techniques and supportive care aims to maximize therapeutic benefit while minimizing these toxicities.
"Localized anal cancer is often highly curable, but it requires a multidisciplinary approach with therapies carefully tailored to each patient based on their tumor stage and anatomy," said Brian G. Czito, MD, FASTRO, chair of the guideline task force and a professor of radiation oncology at Duke Cancer Center. "Our task force examined decades of research to develop this guideline, distilling best practices and their underlying evidence into clear recommendations that help treatment teams deliver therapy at the right dose to eliminate the cancer while preserving the patient's quality of life."
"Radiation therapy plays a central role in managing anal cancer, offering patients an effective, organ-preserving definitive treatment," said Mary Feng, MD, FASTRO, vice chair of the guideline task force and a professor of radiation oncology at the University of California San Francisco. "Newer radiation techniques offer heightened precision, allowing us to target these tumors more closely and decrease side effects without compromising treatment effectiveness."
The guideline's evidence-based recommendations address indications for radiation therapy, concurrent systemic therapy and surgery for patients with localized anal SCC. The guideline also details optimal dosing, techniques and treatment planning for radiation therapy, as well as strategies for post-treatment assessment and care. Key recommendations are as follows:
For most patients with localized anal cancer, the recommended course of definitive treatment is radiation therapy with concurrent 5-fluorouracil (5-FU) plus mitomycin (MMC). Possible alternatives for systemic therapy include capecitabine as a substitute for 5-FU and cisplatin for MMC; additional details on systemic therapy are available in a complementary guideline developed by the American Society of Clinical Oncology (ASCO) with participation from ASTRO.
Diversion surgery before chemoradiation may be considered for patients with intestinal obstruction or other symptoms that could compromise their likelihood of completing definitive treatment. The guideline also discusses local excision as an alternative to chemoradiation for carefully selected patients diagnosed with very early-stage disease without higher-risk histologic features.
Intensity modulated radiation therapy (IMRT) with daily image guidance is recommended over conventional, three-dimensional conformal radiation therapy (3D-CRT) techniques to minimize treatment-related side effects. Recommendations also specify optimal radiation targets, dosing and fractionation techniques for the primary tumor and nearby lymph nodes, as well as guidance for normal organ dose constraints and for minimizing treatment breaks.
Close monitoring after treatment is recommended to assess the patient's response to chemoradiation and guide subsequent decision-making. The guideline examines timing for post-treatment surveillance methods such as clinical exams, endoscopy and advanced imaging.
About the Guideline
"Radiation Therapy for Anal Squamous Cell Carcinoma: An ASTRO Clinical Practice Guideline" was based on a systematic review conducted by the Agency for Healthcare Research and Quality (AHRQ) of articles published from January 2000 to May 2023. The multidisciplinary guideline task force included radiation, medical and surgical oncologists, a medical physicist and a patient representative. The guideline was developed in collaboration with ASCO and the Society of Surgical Oncology, and it is endorsed by the European Society for Radiotherapy and Oncology and the Royal Australian and New Zealand College of Radiologists.
ASTRO's clinical guidelines are intended as tools to promote appropriately individualized, shared decision-making between physicians and patients. None should be construed as strict or superseding the appropriately informed and considered judgments of individual physicians and patients.
Patient Resources on RT for Anal Cancer
- Videos: Radiation Therapy for Colon, Rectum and Anus Cancers ; ( Spanish ); An Introduction to Radiation Therapy ( Spanish )
- Handout: Radiation Therapy for Colon, Rectum and Anus Cancers
- More patient information on radiation therapy: Radiation Therapy in Focus , RT Answers
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