Anal canal cancer is a relatively rare disease, representing 1.2% of digestive cancers and 6% of anorectal cancers. Incidence is less than 1/100 000 of the general population. However, the incidence has increased considerably over the past three decades. The main risk factors are HPV infections and smoking. Initial treatment comprises radiochemotherapy or radiotherapy alone, according to the patient's tumor stage and tolerance of chemotherapy. The choice of the most appropriate treatment strategy will condition the patient's prognosis. Consequently, early assessment of the initial extension of the tumor, its therapeutic response and relapses constitute determining factors in the management of the disease Despite the good results obtained, persistent disease is observed in 30% of cases and abdominal-pelvic salvage amputation can then prove effective in cases of local or loco-regional relapse. The great majority of relapses occur within 2 years after treatment. Reported prognostic survival factors are the T stage, size inferior or superior to 4 cm and inguinal or pelvic lymph node involvement.

The rules for follow-up are not substantiated by high levels of proof. Follow-up focuses principally on the clinical examination although the type and frequency of the paraclinical examinations are not backed by any consensus.

Post-treatment 18-FDG PET scan at 2 months can prove useful to predict locoregional or metastatic recurrence in patients treated by radiochemotherapy or radiotherapy in the anal canal cancer setting. There appear to be an FDG intensity variable and a metabolic response criterion enabling establishment of two groups of patients: low recurrence risk versus high recurrence risk at 2 years.

Inclusion Criteria:

• Consecutive inclusion of incident cases of anal canal cancer between November 2014 and May 2018. These patients are volunteers and have signed informed consent.

Exclusion Criteria:

• Presence of a nother cancer and specific treatment (chemotherapy, radiotherapy). Follow-up impossible during two years or more.

Refusal to submit to initial or post-treatment PET/CT.

Canal anal cancer