SAN DIEGO — For patients with non-small-cell lung cancer, a simple PET/CT protocol can enhance the precision of traditional staging, which could lead to more appropriate management, according to new research presented here at the Society of Nuclear Medicine and Molecular Imaging 2016 Annual Meeting.
Whole-body tumor volume on PET/CT is a quantitative three-dimensional measurement of a patient's tumor burden that can lead to a more accurate prognosis when "used as an adjunct to the traditional clinical staging system," said investigator Joshua Finkle, MD, from the University of Chicago.
The additional information could spur changes to survival estimates, effectively upstaging or downstaging patients to a more appropriate prognostic group than the TNM staging system that accounts for one-dimensional tumor size, but not three-dimensional volume, he told Medscape Medical News.
For example, a patient who presents with distant metastases, categorized as TNM stage IV, might have a better prognosis than expected if the PET/CT protocol reveals a low whole-body metabolic tumor volume.
"The treating physicians may then feel comfortable with more aggressive treatment options — such as surgery and chemoradiation — rather than palliative therapy, which is often used for stage IV disease," said Dr Finkle.
Three-Dimensional Measure of Tumor Burden
The researchers retrospectively evaluated 884 patients newly diagnosed with non-small-cell lung cancer from 2004 to 2015. They assessed clinical TNM stage, initial PET whole-body metabolic tumor volume, and long-term survival.
When patients in each TNM stage were stratified by metabolic tumor volume, there were no significant changes in prognosis for patients with stage I or II disease. However, for patients with more advanced disease, about half could be upstaged or downstaged on the basis of additional information.
For example, for about half of the patients with stage IIIa disease and low whole-body tumor volume, the rate of overall survival closely resembled that for patients with stage IIb disease (P = .26), but was significantly different than for patients with stage IIIb disease (P < .001).
"Effectively, these patients could be downstaged to IIb disease," Dr Finkle explained.
And for patients with stage IIIa disease and a metabolic tumor volume above the median, the rate of survival was significantly different than that for patients with stage IIb disease (P = .009), but not for patients with stage IIIb disease (P = .40), meaning that these patients could be upstaged to IIIb.
More patients presented with advanced disease (stage III or IV) than with early disease (stage I or II) (66% vs 34%).
"I think it's going in the right direction. This should be considered for incorporation into the new staging system [the 8th edition of the TNM classification]," said session moderator Victor Gerbaudo, PhD, from Brigham and Women's Hospital and Harvard Medical School in Boston.
However, "there are some limitations that we will need to overcome," he added.
"The community needs to come together because the calculation of metabolic tumor volume will need to be standardized around the world," Dr Gerbaudo told Medscape Medical News. He pointed to the 2006 National Cancer Institute consensus guidelines for the use of ¹⁸F-FDG PET to gauge therapeutic response, which standardized research protocols for PET in oncology (J Nucl Med. 2006;47:1059-1066).
In their study, Dr Finkle and his colleagues stratified patients on the basis of tumor volume in relation to the median (above or below).
"The main thing going forward with these results is that we are going to adjust the cutoff values," Dr Finkle reported. "We used median values as a proof of concept," but future research "will give us more accurate cutoffs."
Dr Finkle and Dr Gerbaudo have disclosed no relevant financial relationships.
Society of Nuclear Medicine and Molecular Imaging (SNMMI) 2016 Annual Meeting: Abstract 186. Presented June 12, 2016.
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Cite this: PET/CT Sharpens Lung Cancer Staging, Prognosis - Medscape - Jun 15, 2016.
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