Localised anal canal disease
Definitive concurrent chemoradiation is standard for most stage I to III anal canal cancers.
A widely used regimen is:
Mitomycin 10 mg/m² IV on days 1 and 29
plus
Fluorouracil 1000 mg/m²/day by continuous IV infusion on days 1 to 4 and 29 to 32
with concurrent pelvic radiation.
An oral fluoropyrimidine alternative is:
Capecitabine 825 mg/m² orally twice daily on radiotherapy days
combined with mitomycin.
Radiation dose is tailored to stage and commonly lies in the range of approximately 45 to 59.4 Gy, with treatment of the primary tumour and appropriate pelvic and inguinal nodal regions.
Response
Do not declare chemoradiotherapy failure too early.
Tumours may continue regressing for several months after treatment. In the absence of clear progression, allow clinical response to mature, with definitive response assessment often continuing toward approximately 26 weeks from treatment initiation.
Salvage surgery
Biopsy proven persistent or locally recurrent disease after adequate chemoradiotherapy requires salvage abdominoperineal resection when an R0 resection is achievable.
Prior radiotherapy causes substantial perineal wound morbidity. Large perineal defects frequently benefit from vascularised flap reconstruction.
Metastatic disease requires systemic treatment and biomarker informed oncology management.
