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

23 Anal Cancer

William Gehin, Didier Peiffert, Emilie Meknaci

1. Summary 2. Introduction 3. Anatomy 4. Pathology

3 3 3 4 4 6 8 9

9. Treatment planning

9 9

10. Dose, dose rate and fractionation

11. Monitoring

11 12 12 13 14

12. Results

5. Work up

13. Adverse Events 14. Key messages 15. References

6. Indications, contra-indications 7. Tumour and target volumes

8. Technique

1. SUMMARY

Squamous cell carcinoma of the anus is a rare cancer that is usually treated with concurrent chemoradiation with good rates of sphincter preservation, disease free (DFS) and overall survival (OS). Interstitial brachytherapy (IBT) after concurrent chemoradiation offers high local control and anal sphincter preservation rates with acceptable toxicity. Clinical target volume (CTV) consists of the initial gross tumour volume (GTV) and adjacent areas at risk and the loco-regional lymph nodes, with a dose of 45 to 50 Gy with a sequential boost delivered by either external beam radiation therapy (EBRT) or by IBT to the CTV. There is no agreement for the boost technique, but IBT is the only technique that can limit the high dose boost zone to a segment of the anal circumference. The standard IBT remains mainly based on pulsed-dose rate (PDR) techniques, and recently high-dose rate (HDR) brachytherapy has been increasingly used for anal canal cancer management.

Relapse most commonly occurs locally, with radical surgery required to achieve cure.

2. INTRODUCTION

a standard, even for large tumours, while abdominal-perineal resection is reserved for patients with local failure after previous irradiation. Questions remain, however, about the most effective and least toxic doses of radiotherapy and chemotherapy, and the role of brachytherapy, although widely used with good results, is not fully defined yet, due to the lack of comparative studies.

Anal cancer is an uncommon disease accounting for approximately 3% of all gastrointestinal cancers [2]. Epidemiologic studies from the United States, Northern and Western Europe, and Australia have reported an increased incidence of anal cancer in the past 30 to 40 years, perhaps due to changes in sexual behaviors, increased incidence and persistence of human papilloma virus (HPV) infection in the anal region, and increased prevalence of human immunodeficiency virus (HIV) infection. The incidence has increased without clear improvement in survival even if distant metastases occur in only 10% of cases at diagnosis [3]. Anal canal cancer has been considered as a life deteriorating event when cured because of sphincter amputation caused by historical surgical treatment. The impact on quality of life has pushed clinicians to consider new ways of treatment. Thus, prospective randomized trials have been conducted and have led to the adoption of a combination of external beam radiotherapy (EBRT) and chemotherapy (mainlyMitomycin and 5-Fluorouracil) as the current standard of care for patients with anal cancer. Conservative treatments for sphincter preservation have therefore become

3. ANATOMY

The anal canal is the most terminal part of the gastrointestinal tract (figure 1). It lies completely extraperitoneally, within the anal triangle of the perineum between the right and left ischioanal fossae, and its overall length is between 3 to 4 cm. It ends at the anal verge, whichmarks the junction of the anal canal and the external hair-bearing skin. The anal margin (or perianus) is described as a 5-cm radius of that hair-bearing perianal skin.