Nuclear medicine physicians have suspected since the advent of PET/CT that the hybrid technology would outperform PET or CT for staging cancer. Those suspicions were confirmed Tuesday by a study of 260 patients at the University of Essen, Germany, which showed that PET/CT is substantially more accurate for staging carcinoma than PET or CT alone and PET and CT viewed side by side.

The modality-versus-modality trial indicates that PET/CT can be recommended as a first-line diagnostic tool for various cancers, said Dr. Patrick Veit, a research fellow who presented the study on behalf of its principal investigator, Dr. Gerard Antoch, an attending physician in the university's radiology department.

The study involved 112 patients who were scanned for primary tumor stages and 148 who were imaged to investigate suspected recurrent disease. Cases of lung, head and neck, GI tract, liver, thyroid, uterine, and GI cancers were included in the mix.

Readings were aimed at detecting primary or recurrent tumor, and analyses were completed for overall and separate TNM staging. The physicians also assessed the scans' impact on patient management. The distribution of patients for T-stage, N-stage, and M-stage histology was 77, 72, and 57, respectively. The average follow-up was 311 days.

PET/CT correctly staged 63 of the T-stage patients, significantly more than the 55 who were correctly staged with side-by-side PET and CT (PET+CT) and with CT or PET alone.

Of the N-stage patients, PET/CT staged 240, again significantly more than PET+CT and CT or PET alone.

PET/CT was correct for 248 M-stage patients and was significantly more adept than PET and CT viewed separately, but it was no better than PET+CT in these cases.

Overall TNM-stage results indicated that 218 patients were correctly staged with PET. It was significantly better than PET+CT, PET, and CT. P values quantifying the magnitude of statistical significance for all three sets of comparisons were in the 0.0001 range, Veit said.

PET/CT would have altered patient management regardless of which approach was used for initial staging, based on German clinical guidelines for prescribing therapy, he said. It would hypothetically have changed the therapeutic recommendation in 17% of the cases if it had been used as a follow-up procedure after PET-based staging. Seventeen percent of cases initially examined with CT and 6% of patients evaluated with PET+CT would have been prescribed different therapies.

Whole-body imaging performed in the trial consisted of imaging from the head to the upper thighs. Oral and intravenous contrast media enhanced CT imaging. For PET, 350 MBq of fluorine-18 FDG was administered an hour before scanning. CT was also used to correct PET attenuation.

Patients were examined with a single PET/CT study. PET and CT images were then drawn from that data set to form the basis for comparison.

The PET images were interpreted by two nuclear medicine specialists visually and then quantitatively based on standard uptake values. The thresholds of malignancy for intrahepatic and extrahepatic lesions were SUVs of at least 2.5 and 3.5, respectively. Two radiologists examined the CT scans. Lymph nodes were assessed by size.

Side-by-side PET and CT analysis was performed simultaneously by a radiologist and nuclear medicine specialist. Increased glucose metabolism was considered evidence of pathology. Determinations of lymph node involvement in this instance was independent of size. The same approach was applied when evaluating PET/CT images, Veit said.