Contribution of co-registered PET/CT for patients with suspected recurrence of colo-rectal cancer

Positron emission tomography using 18F fluorodeoxyglucose (PET) has proved to offer advantages for patients presenting with suspected recurrence of colo-rectal cancer. However; this examination is confronted with two disadvantages: the lack of anatomical reference marks and the presence of physiological uptake that can be difficult to locate. We carried out a retrospective study on 30 patients with suspected recurrence of Colo-rectal cancer in order to evaluate the diagnostic and therapeutic impact of PET/CT fusion images compared with PET alone. PET/CT acquisitions were performed on a prototype Positrace or on a double-detection head gamma camera in coincidence Hawkeye. PET/CT fusion images had a formal diagnostic impact for 6 patients out of 30 (20%), including 5 patients out of 12 (41%) having a suspected pelvic recurrence. In five cases, it allowed us to resolve ambiguities about whether the site of recurrence was located in the bone or the soft tissues. Furthermore, in one case we were able to locate an intra-abdominal uptake focus at the level of the liver. The PET/CT fusion images had a probable diagnostic impact for three additional patients. For two patients, the PET/CT fusion images allowed us to identify an ambiguous uptake focus as being related to physiological renal uptake. For 4 patients out of 30 (13%), the PET/CT fusion images had a clear additional therapeutic impact, including 4/12 (33%) for whom a pelvic recurrence could be suspected. The present study shows that PET/CT fusion images have an important diagnostic and therapeutic impact for patients with suspected recurrence of colorectal cancer; the impact becoming major for the subgroup of patients having a suspected pelvic recurrence. (author)