FDG-PET May Help Predict Lung Cancer Survival

Analysis of ¹⁸F fluorodeoxyglucose positron emission tomography (FDG-PET) standardized uptake values may be a useful technique for predicting survival in patients with inoperable stage III non–small-cell lung carcinoma (NSCLC), according to a study published in the Journal of Clinical Oncology.

NSCLC is the most common and deadly form of lung cancer. Inoperable, stage III tumors have a poor prognosis, and the standard of care for patients is currently chemoradiotherapy, a combination of radiation and platinum-based agents. Unfortunately, follow-up of patients following this treatment regimen has been challenging. Computed tomography is the current imaging method of choice, but following radiation the data can be difficult to interpret. Patients may appear healthy using computed tomography while malignant growth continues.

A more sensitive method for detecting response to therapy is FDG-PET. It is the more appropriate imaging modality for detecting metastases and metabolically-active remnants of tumors. To this end, the researchers from the department of radiology at Case Western Reserve University hypothesized that FDG-PET could be used as a biomarker to predict the chance of survival in patients following chemoradiotherapy.

The work described in the paper was a prospective study of 173 patients with stage III NSCLC recruited across 37 institutions. These patients received prior radiotherapy plus platinum-based chemotherapy without surgery and FDG-PET follow-up. They were then followed for at least 2 years in order to compare fluorodeoxyglucose uptake with overall survival. In order to quantify uptake, standardized uptake values (SUVs) were calculated in one of two ways. SUV_max was the maximal pixel density at the brightest point of a region of interest. SUV_peak was the average signal within a region of interest that included the brightest pixel. The value of 3.5 SUVs was selected as a binary cutoff to determine “high” and “low” signals.

The researchers noted that method of determining SUVs did not make a significant difference in any of the results. No significant association between “high” SUV and survival could be calculated. When these data were analyzed using a continuous variable model, however, a significant survival benefit was observed (HR = 1.087). In addition, when the authors explored a cutoff of 5 instead of 3.5, the survival advantage was improved (HR = 1.713, using a univariate analysis). In addition, SUVs failed to correlate with survival when taken prior to chemoradiotherapy.

In all, this study suggested that FDG-PET may be a suitable technique for predicting survival following chemoradiotherapy for inoperable stage III NSCLC. Unfortunately, cutoff criteria could not be ascertained from the data; this aspect of the technique must be explored further. “Using a simple post-treatment SUV_peak (or SUV_max) cutoff of 3.5 after chemoradiotherapy is not valuable for clinical decision-making…Our data do suggest that high post-treatment SUV portends a poor outcome,” the authors concluded.