FDG-PET parameter predicts locally advanced lung cancer survival

High post-treatment concentrations of a radioactive imaging marker are predictive of worse overall survival from inoperable, locally advanced non-small-cell lung cancer (NSCLC), prospective study findings suggest.

As published in the Journal of Clinical Oncology, patients whose tumors had a higher uptake of [18F]fluorodeoxyglucose (FDG) on positron emission tomography (PET) scanning after chemoradiotherapy were more likely to have died at 2 years than other patients.

“One challenge with concurrent chemoradiotherapy is difficulty ascertaining disease status soon after treatment,” say the study investigators Mitchell Machtay (Case Western Reserve University and University Hospitals Case Medical Center-Seidman Cancer Center, Cleveland, Ohio, USA) and colleagues.

They add: “Given the value of PET in other settings, we hypothesized that it would be useful as a biomarker to assess response after chemoradiotherapy.”

The researchers note that while computed tomography (CT) of the chest can be performed, the results are often difficult to interpret and patients may still have active disease that the CT scan does not pick up after their treatment.

For their trial, the researchers recruited patients with inoperable stage III NSCLC and no evidence of stage IV disease by conventional CT imaging of the chest or abdomen, bone, or brain scans. FDG-PET was performed at enrolment and 2 weeks after patients had received concurrent, platinum-containing chemoradiotherapy. FDG uptake was expressed as a standard uptake value (SUV) in the primary tumor, lymph nodes, and common sites of distant metastases.

Out of 250 enrolled patients, 173 with a median age of 65 years had both pre- and post-chemoradiotherapy FDG-PET data available for analysis. The 2-year overall survival rate for the entire population was 42.5%.

While the mean peak SUV measured before treatment did not correlate with patient survival, the post-treatment value did. Using a pre-specified SUV of 3.5 as the cutoff point for high or low FDG uptake, the researchers found that 47% of patients with tumors with an SUV of over 3.5 survived for 2 years, compared with 51% of patients with tumors with an SUV of 3.5 or greater. Although this was not a statistically significant difference at first, further multivariate analysis of the peak SUV as a continuous variable showed it was significantly associated with survival (hazard ratio = 1.09).

The team also performed exploratory analyses using higher SUV thresholds (≥5 and ≥7) and found that these values were significantly predictive of overall survival, but it was not possible to identify a single cutoff value from the present research.

“Although post-treatment FDG-PET seems to provide prognostic information, it is not yet known whether subsequent treatment decisions based on this information can improve clinical outcomes,” Machtay and team conclude. Further research is needed in this clinical setting, they propose.

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