PET may help improve patient management in recurrent colorectal cancer

PET scans may help detect recurrent colorectal cancer and provide useful prognostic information.

Researchers from Austin Hospital, Wesley Hospital and other sites in Australia conducted a multicenter, prospective study to determine the effects of PET on changes in disease management in patients with recurrent colorectal cancer.

The study included 191 patients with a mean age of 66 years. The researchers divided patients into two groups: those with residual structural lesions (group A, n=93) and those with hepatic or pulmonary metastases (group B, n=98). The researchers performed PET on all patients.

PET detected additional disease sites in nearly half of the participants in each group (group A: 48.4%; group B: 43.9%). Based on the results of PET, management plans changed in 65.6% of patients in group A (95% CI, 56.0-75.3) and 49% in group B (95% CI, 39.1-58.9).

At follow-up, the researchers identified progressive disease in 60.5% of patients in group A who had additional lesions detected on PET and in 36.2% of patients with no additional lesions detected on PET (P=.04).

In group B, the researchers identified progressive disease in 65.9% of those with additional lesions detected on PET and 39.2% of those with no additional lesions detected (P=.01).

Patients in both groups were better stratified into curative and palliative groups following PET, compared with stratification prior to PET, according to the researchers.

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

My concern is that this study is written predominantly by nuclear medicine doctors, from the nuclear medicine perspective, and not by oncologists, from an oncologist's perspective. There is an oncologist involved, but it is mostly done at nuclear medicine facilities, and I'm concerned that the pre-trial tendency was likely to have assumed that PET was useful. A major flaw in how the study was conducted is that the oncologists who declared their intention before the PET were not really investigators in the trial. In my opinion, it would be important to carefully review whether the clinical situation supported what the doctors said was the pre-PET plan. Looking at some of the plans they outlined, I'm skeptical about whether or not these were truly well though-out plans, or a quick answer to a study question that was not the focus of their attention. Some people at our institution tried a similar concept where they basically asked doctors who ordered a PET, why are you getting it? And asked then afterwards: Did the PET change your management? Gosh, every doctor said it did. Because it's really like asking, "Dear Doctor, that expensive test you ordered, was it a waste of money or was it in fact a smart thing?" Not a single doctor felt that they wasted a penny. It's an invalid way of studying the question. What you'd really need is a very critical review of what the well thought-out treatment plan was before PET, and how the PET might change it. A pre-test outline of what the question is that PET is being gotten for, and what the action will be for a negative PET and positive PET in advance, would be a better way to outline PET's utility.

– Leonard B. Saltz, MD

Professor of Medicine at the Weill Medical College of Cornell University
Attending Physician at Memorial Sloan-Kettering Cancer Center