PET Scans for Recurrent Colorectal Cancer

September 10, 2008 — The use of positron emission tomography (PET) scans led to changes in disease management for more than half of all patients with suspected or proven recurrent colorectal cancer, according to the results of a study published in the September issue of the Journal of Nuclear Medicine.

In this large multicenter trial, PET scanning detected additional disease sites in 48.4% of patients in 1 study group (group A) and in 43.9% of patients in the second study group (group B). The use of PET scanning also changed the planned disease management in 65.6% of patients in group A and 49.0% of those in group B.

"The data from our study, as well as from other studies, clearly demonstrates that PET can alter management decisions, and in many meaningful ways," lead study author Andrew M. Scott, MD, director of the Centre for PET and the Ludwig Institute for Cancer Research, Austin Hospital, Melbourne, Australia, told Medscape Oncology in an interview. "It can help confirm the presence of disease, identify additional sites of disease, and assist in making the most appropriate treatment decisions."

"It should be emphasized that some patients have isolated disease that can be resected, which will allow them to have long progression free survival periods or even a potential cure," Dr. Scott added. "PET scanning can more appropriately identify patients that will benefit from these treatments."

Prompted Changes in More Than Half of Patients

PET scans have been shown to demonstrate a high degree of accuracy in the detection of recurrent and metastatic colorectal cancer, and although sensitivity is comparable with a computed tomographic (CT) scan in the detection of metastases to the liver, it is superior in the detection of extrahepatic disease. Previous reports estimate that the use of PET has changed estimates of the extent of disease in approximately one third of patients and that it can influence management decisions in patients with metastatic colorectal cancer.

However, few prospective studies evaluating the use of PET in patients with recurrent colorectal cancer have been performed, and none have been large multicenter trials. The study authors note that the effect of PET on patient outcomes, such as progression-free survival, has also not been previously reported.

The goal of the current trial was to evaluate the effect of PET on management change in patients with proven or suspected recurrent colorectal cancer and to assess the effect of management change on disease-free survival.

A total of 191 patients from 4 institutions were enrolled in the study between November 23, 2003, and August 12, 2004, and they were subsequently separated into 2 study groups. Group A consisted of 93 symptomatic patients with a residual structural lesion suggestive of a recurrent tumor, whereas group B consisted of 98 patients with potentially resectable liver or lung metastases.

Lesions Detected by PET, Management Changes

In group A, 90 (96.8%) patients underwent both PET and CT scans, whereas 3 (3.2%) patients underwent a PET scan only. In group B, 83 (84.7%) patients underwent both PET and CT scans, whereas 15 (15.3%) patients underwent a PET scan only.

Additional disease sites were identified in 45 (48.4%) patients in group A, and in the second group, additional sites were detected in 43 (43.9%) patients. Undergoing a PET scan also resulted in changes in disease management plans. On the basis of PET scan results, 61 (65.6%) patients in group A had management plans altered, and in group B, 48 (49.0%) patients had a change in management plans. In 96% of the patients participating in this study, the treatment management plan that was actually implemented was consistent with the stated post-PET management plan.

Progression-Free Survival

At 12 months, the investigators evaluated clinical outcomes by comparing the progression-free survival of patients in both groups. The researchers found that patients who had additional lesions detected on PET scan had poorer progression-free survival vs those who had conventional imaging. On follow-up, 60.5% of patients in group A had progressive disease, with additional lesions identified by PET scanning vs patients who underwent conventional imaging. In group B, progressive disease was identified in 65.9% of patients with additional lesions that were detected with PET scans.

Patients in group B who had localized disease to the liver or lungs on PET scan had a better prognosis vs those with more disseminated disease. The researchers also noted that these data clearly showed the powerful prognostic ability of PET to accurately stratify patients who are thought to have localized disease on conventional imaging. Stratification into curative and palliative groups was also improved after PET scans for patients in both groups. In addition, those in group B who planned to have surgery after undergoing a PET scan had superior progression-free survival vs patients who planned surgery before undergoing a PET scan.

"The data from our study shows that using PET scanning can impact outcomes and therapeutic decisions, and while our study did not look at cost effectiveness, there is substantial data showing that PET scanning is cost effective," said Dr. Scott.

Inappropriate treatment not only has a substantial effect on patient well-being, but also can be very costly, Dr. Scott emphasized. "PET scanning can contribute to more appropriate treatment decisions and ultimately be cost saving, but that was not specifically examined in our study."

This study was funded by the Australian Government Department of Health and Ageing.

J Nucl Med. 2008;49:1451-1457.