NEW ORLEANS—Positron emission tomography (PET) scanning is a powerful predictor of survival in patients with non-small-cell lung cancer (NSCLC), reported Michael MacManus, MD, of the Peter MacCallum Cancer Institute, East Melbourne, Australia.
The prospective study, presented at the 36th Annual Meeting of the American Society of Clinical Oncology (ASCO), included 56 patients with inoperable stage IA to IIIB disease. Patients underwent concurrent platinum-based radical chemoradiotherapy (44 cases) or radical radiotherapy alone (12 cases) and PET and CT scans.
Pretreatment and post-treatment scans were coregistered on a screen, and response was evaluated qualitatively by a nuclear medicine physician. Data were recorded prospectively before the patient’s clinical response was known.
As background, Dr. MacManus reminded oncologists that PET’s superiority to CT-based staging in operable lung cancer is already recognized. PET is also superior to conventional staging in candidates for radical radiotherapy and has shown promise in evaluating patients after treatment.
Thoracic CT scanning, on the other hand, is difficult to interpret and correlates rather poorly with outcome after radical radiotherapy. One of the aims of the study was to determine a better means of predicting which patients could benefit from additional therapy after initial treatment.
In many cases, PET scanning revealed information that was different from that obtained by CT scanning. By PET scanning, about half of the patients who appeared to have a complete treatment response on CT scan had evidence of residual tumor, and some patients who demonstrated tumors on CT actually had a complete response on PET, Dr. Mac-Manus said.
“We treated some patients who had PET evidence of metastases, unconfirmed by other means, with radical therapy, and they all failed at sites of PET-detected metastases, so we don’t do that anymore,” he said. “We generally believe the PET scan.”
One-year survival was 58%, and 2-year survival 48%. Complete responses were seen by PET scans in 43% of patients; a partial response was seen in 41%; stable disease was noted in 7%, and disease progressed in 9%.
PET scanning predicted survival. Actuarial survival was 84% at both 1 and 2 years for the 24 patients (43%) who achieved a complete response on PET, and 43% and 31%, respectively, for the patients who did not achieve a complete response. Median survival for all patients was 14 months. Survival was strongly correlated with a favorable response by PET scan; it was not correlated with chemotherapy response.
Dr. MacManus gave the mortality hazard ratios from the multivariate analysis according to the patients’ response on PET scan: 1.0 for complete response, 2.97 for partial response, 3.92 for no response, and 78.7 for progressive disease. These results were highly statistically significant, he said.
Dr. MacManus concluded, “PET response to radical chemoradiotherapy separates patients into groups with widely differing survival probabilities. Early CT scanning results did not correlate strongly with survival. Response less than a complete response was associated with relatively poor survival. PET may identify patients who are suitable for salvage therapy, but we need longer follow-up to see what happens with these patients.”
