Abstract
PurposeThe role of hybrid imaging using 18F-fluoro-2-deoxy-D-glucose positron-emission tomography (FDG-PET), computed tomography (CT) and magnetic resonance imaging (MRI) to improve preoperative evaluation of rectal cancer is largely unknown. To investigate this, the RECTOPET (REctal Cancer Trial on PET/MRI/CT) study has been launched with the aim to assess staging and restaging of primary rectal cancer. This report presents the study workflow and the initial experiences of the impact of PET/CT on staging and management of the first patients included in the RECTOPET study.MethodsThis prospective cohort study, initiated in September 2016, is actively recruiting patients from Region Västerbotten in Sweden. This pilot study includes patients recruited and followed up until December 2017. All patients had a biopsy-verified rectal adenocarcinoma and underwent a minimum of one preoperative FDG-PET/CT and FDG-PET/MRI examination. These patients were referred to the colorectal cancer multidisciplinary team meeting at Umeå University Hospital. All available data were evaluated when making management recommendations. The clinical course was noted and changes consequent to PET imaging were described; surgical specimens underwent dedicated MRI for anatomical matching between imaging and histopathology.ResultsTwenty-four patients have so far been included in the study. Four patients were deemed unresectable, while 19 patients underwent or were scheduled for surgery; one patient was enrolled in a watch-and-wait programme after restaging. Consequent to taking part in the study, two patients were upstaged to M1 disease: one patient was diagnosed with a solitary hepatic metastasis detected using PET/CT and underwent metastasectomy prior to rectal cancer surgery, while one patient with a small, but metabolically active, lung nodulus experienced no change of management. PET/MRI did not contribute to any recorded change in patient management.ConclusionsThe RECTOPET study investigating the role of PET/CT and PET/MRI for preoperative staging of primary rectal cancer patients will provide novel data that clarify the value of adding hybrid to conventional imaging, and the role of PET/CT versus PET/MRI.Trial registrationNCT03846882.
Highlights
Imaging is of paramount importance when tailoring treatment strategies in patients with rectal cancer
Impact of FDG-Positron-emission tomography (PET)/computed tomography (CT) on radiological tumour stage and clinical management All 24 patients included in this initial study population underwent fluoro-2-deoxy-D-glucose positron-emission tomography (FDG-PET)/CT with a median time interval from FDG injection to examination of 60 min, followed by PET/magnetic resonance imaging (MRI) with a median time interval from FDG injection to examination of 122.5 min
MRI of the liver confirmed the diagnosis of a solitary liver metastasis, upstaging this patient with a cT2N0 tumour from M0 to M1
Summary
Imaging is of paramount importance when tailoring treatment strategies in patients with rectal cancer. Together with clinical examination and endoscopy, magnetic resonance imaging (MRI) of the pelvis is essential both in the initial setting and in restaging [1,2,3], providing assessment of the four main risk factors for disease recurrence: the extent of the primary tumour (T stage); metastases to locoregional lymph nodes (N stage); the presence of extramural venous invasion (EMVI); and the distance from the primary tumour to the mesorectal fascia (MRF). Of these risk factors, the N status is the most challenging to evaluate [4,5,6,7,8]. In patients with a clinical complete response or near complete response after neoadjuvant therapy (short-term radiotherapy [RT], chemoradiotherapy [CRT] and chemotherapy), organ-saving strategies such as local excision and the watch-and-wait approach are valid options [2, 12], highlighting further the importance of accurate restaging after neoadjuvant treatment
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