The emerging role of FDG PET/CT in rectal cancer management: is it time to use the technique for early prognostication?

Abstract

# Springer-Verlag Berlin Heidelberg 2013 Colorectal cancer is the second leading cause of death and the fourth most commonly diagnosed cancer in the USA [1]. One form, rectal cancer, defined as cancer growing within 12 cm of the anal verge [2], is challenging because of its unique anatomical characteristics, critical position and therapeutic options (aimed at preserving pelvic floor integrity, sphincter continence and genitourinary functions). General considerations and staging proceduresWhen a patient is diagnosed with rectal cancer, staging procedures, performed to evaluate global and specific therapeutic risk, include: complete bowel endoscopy (to identify possible synchronous tumours), rigid proctoscopy (to establish the exact level of the lesion), carcinoembryonic antigen (CEA) test and a full clinical examination (to determine performance status). Moreover, for a complete evaluation of the disease, including possible distant metastases, a contrast-enhanced (ce) CT of the thorax, abdomen and pelvis, with administration of oral and IV contrast media, must also be performed. In some circumstances, rectal wall invasion and the presence of pathologic lymph nodes can be assessed by endoscopic ultrasound (EUS) and ceMRI of the pelvis [3]. In a meta-analysis of 90 studies, performed to compare the clinical performance of EUS, MRI and CT in rectal cancer staging, Bipat et al. found EUS and MRI to show similar sensitivity in the diagnosis of muscularis propria invasion (94 %), while EUS was more accurate in the evaluation of local tumour invasion (86 vs 69 %); ceCT, on the other hand, is not considered a gold standard investigation for evaluating tumour wall penetration. Local lymph node involvement, which constitutes a major challenge in rectal cancer staging, can be effectively evaluated by using all three methods, even though only ceCT and MRI provide information on distant node status and metastasis [4]. An advantage of MRI is that it allows better evaluation of the mesorectum, while a relative disadvantage of EUS is its relatively high dependence on operator skill. Pathologic considerationsHistopathologic analysis of resected lesions is also an important part of staging, both initial staging and restaging after neoadjuvant therapy. The final report should contain the following information: a gross description of the tumour burden,

Positron Emission Tomography (PET) in Oncology

“…FDG-PET/CT is not routinely used in the staging of colorectal cancer, but could be proposed for problem solving, or in the presence of CEA elevation or resectable metastases [ 28 ], as proposed in the National Comprehensive Cancer Network guidelines (NCCN version 4.2013 [ 29 ]). Actually, for the local T staging, MRI and endorectal ultrasound (ERUS) are recommended [ 30 ]; for the detection of colorectal metastases (N and M staging), the most frequently used modalities are US, CT, MRI and FDG-PET/CT [ 31 ].…”

18 F-FDG PET/contrast enhanced CT in the standard surveillance of high risk colorectal cancer patients

“…According to the National Comprehensive Cancer Network NCCN Guideline [4], PET/CT scanning is not routinely indicated both in the staging and in the follow-up of CRC, however it is indicated in the setting of serial increased CEA and resectable metastases, in order to identify other localizations and avoid invasive procedures [9]. Nevertheless, some investigators suggest that in certain clinical circumstances, like the initial staging of primary rectal cancer, FDG PET/CT could change the previous staging up to 39% of the patients and lead a management change in 18-24% of patients by demonstrating unsuspected metastatic disease or clarifying the nature of indeterminate lesions [10,11].…”

The role of 18F-fluorodeoxyglucose positron emission tomography/computed tomography in the primary staging of rectal cancer

“…Of the available technologies, computed tomography (CT), magnetic resonance imaging (MRI), and endorectal ultrasound (ERUS) have evolved as the best modalities for accurately staging rectal cancer. In addition, fluorine-18 fluorodeoxyglucose positron emission tomography combined with computed tomography (PET/CT) is widely used not only for preoperative staging, but also for assessing the oncologic outcomes of rectal carcinoma [5-8]. Although several studies reported that the addition of 18 F-FDG PET/CT to conventional imaging methods might alter the treatment algorithm [9], in a recent study, Cipe et al concluded that routine use of 18 F-FDG PET/CT for preoperative staging does not impact the disease management of 96.8% of patients [10].…”