FDG-PET/CT in the Radiotherapy Treatment Planning of Locally Advanced Anal Cancer: A Monoinstitutional Experience

Clelia Di Carlo; Maika di Benedetto; Lisa Vicenzi; Sara Costantini; Francesca Cucciarelli; Francesco Fenu; Eleonora Arena; Cristina Mariucci; Maria Montisci; Valeria Panni; Fabiola Patani; Marco Valenti; Andrea Palucci; Luca Burroni; Giovanna Mantello

doi:10.3389/fonc.2021.655322

FDG-PET/CT in the Radiotherapy Treatment Planning of Locally Advanced Anal Cancer: A Monoinstitutional Experience

Front Oncol. 2021 Jul 1:11:655322. doi: 10.3389/fonc.2021.655322. eCollection 2021.

Authors

Affiliations

¹ Department of Radiation Oncology, Ospedali Riuniti Umberto I°, GM Lancisi, G Salesi, Ancona, Italy.
² Department of Medical Physics, Ospedali Riuniti Umberto I°, GM Lancisi, G Salesi, Ancona, Italy.
³ Department of Nuclear Medicine, Ospedali Riuniti Umberto I°, GM Lancisi, G Salesi, Ancona, Italy.

Abstract

Aims: Radiotherapy with concurrent 5-fluorouracil/mitomycin-C based chemotherapy has been established as definitive standard therapy approach for anal cancer. Intensity Modulated Radiotherapy (IMRT) leads to a precise treatment of the tumor, allowing dose escalation on Gross Tumor Volume (GTV), with a surrounding healthy tissues sparing. Our study assessed the impact of 18-Fluorodeoxyglucose positron emission tomography (18FDG-PET/CT) on the radiotherapy contouring process and its contribution to lymphatic spread detection, resulting to a personalization of Clinical Target Volume (CTV) and dose prescription.

Methods: Thirty-seven patients, with histologically proven squamous cell carcinoma of the anal canal (SCCAC) were analyzed. All patients were evaluated with history and physical examination, trans-anal endoscopic ultrasound, pelvis magnetic resonance imaging (MRI), computed tomography (CT) scans of the chest, abdomen and pelvis and planning 18FDG-PET/CT. The GTV and CTV were drawn on CT, MRI and 18FDG-PET/CT fused images.

Results: Thirty-four (91%) out of 37 patients presented lymph nodes involvement, in one or more areas, detected on 18FDG-PET/CT and/or MRI. The 18FDG-PET/CT showed positive lymph nodes not detected on MRI imaging (PET+, MRI-) in 14/37 patients (38%). In 14 cases, 18FDG-PET/CT allowed to a dose escalation in the involved nodes. The 18FDG-PET/CT fused images led to change the stage in 5/37(14%) cases: four cases from N0 to N1 (inguinal lymph nodes) and in one case from M0 to M1 (common iliac lymph nodes).

Conclusions: The 18FDG-PET/CT has a potentially relevant impact in staging and target volume delineation/definition in patients affected by anal cancer. In our experience, clinical stage variation occurred in 14% of cases. More investigations are needed to define the role of 18FDG-PET/CT in the target volume delineation of anal cancer.

Keywords: 18FDG PET/CT; anal cancer; dose escalation; radiotherapy planning; target volume definition.