Post-treatment ¹⁸F-FDG PET /CT predicts progression-free and cause-specific survival in patients with anal carcinoma

Objectives To evaluate the response to therapy for anal carcinoma with ¹⁸F-FDG-PET/CT and to correlate the metabolic response with patient outcome.

Methods 87 patients with positive biopsy for anal carcinoma were involved in a retrospective multicenter study over a duration of 6 years. Staging was established on clinical examination and CT or MR imaging. About four months after radiochemotherapy, all patients underwent a FDG PET/CT and a clinical examination. The correlation between PET/CT results and progression-free survival and cause-specific survival was calculated using the Kaplan-Meier method.

Results 40 patients were classified T1 or T2 (46%), 43 patients T 3 or T4 (49%), 38 patients N0 (44%), 49 patients with N+ (56%), 20 patients with M1(23%). After a median follow-up of 25 months, 25 patients (29%) presented a recurrence : locally for 9 (10%), at distance for 12 (14%), and both locally and at distance for 4 (4,6%). FDG-PET detected 23 of 25 (92%) cases of clinical progression (local and distant). Thirteen patients (15%) died during the study: 1 with a local recurrence, 12 with metastatic anal carcinoma. Among patients with recurrence, 12 are currently alive.FDG-PET/CT showed complete metabolic response (CR) in 55 patients (63%), partial metabolic response (PR) in 32 (37%): 15 at the initial tumor site (17%), 14 at distance (nodes or metastases) (16%) and 3 both locally and at distance (3%).The cause specific survival rate at 2 years was 100% for CR patients versus 59% for PR patients (P<0.0001). The 2-year progression-free survival for patients with CR and PR was 96% and 28% respectively (p<0.0001).

Conclusions Complete metabolic response on post-treatment FDG-PET/CT is highly predictive of higher progression-free and cause-specific survival. A systematic post-treatment FDG PET/CT might be warranted for the management of patients with anal carcinoma.