Metabolic PET/CT Volumetric Response Evaluation after Chemo(radiation) in Non-Small Cell Lung Cancer

Objectives The usefulness of the response index (RI) of whole-body metabolic tumor volume (MTV_WB) or total lesion glycolysis (TLG_WB) in the evaluation of the therapeutic response to chemo(radiation) therapy in non-small cell lung cancer (NSCLC) (1-5) is controversial. This study tests the utility of the RI of MTV_WB or TLG_WB in evaluating therapeutic response in NSCLC.

Methods 73 non-surgical patients (40 male and 33 female; median age 65.89 years) with NSCLC who had FDG PET/CT scans before and after chemo(radiation) therapy were retrospectively reviewed. The time between the two PET/CT scans varied from 1.4 to 40.4 months. The clinical indication for the post-therapy PET/CT scan was for restaging in 41, evaluating progression in 29, and for unknown reason in 3 patients. The TLG_WB, MTV_WB and SUV_maxWB were measured. Statistical methods included stratified Cox regression modes and Fisher's exact test.

Results There were a total of 53 deaths during follow-up. The median follow-up among survivors was 13.75 months from the post-therapy PET/CT (range: 2.33 to 95.1 months). Median of overall survival of all 73 patients (OS, defined as time from post-therapy PET/CT to death form any cause) was 16.6 months using the Kaplan Meier method (95% CI 9.6 to 21.1 months). There was a statistically significant association of OS and the RI of TLG_WB with hazard ratio (HR) of 0.97 (95% CI 0.95 to 0.99, p=0.02), the RI of MTV_WB with HR of 0.98 (95% CI 0.96 to 1.00, p=0.02) or the RI of SUV_maxWB with HR of 0.92 (95% CI 0.87 to 0.98, p=0.005). There was no statistically significant difference in the clinical indications for the post-therapy PET/CT scans the 4 groups with different quartiles of the distribution of time between the post-therapy PET/CT scans (Fisher's exact, p = 0.15).

Conclusions The RIs of TLG_WB, MTV_WB and SUV_maxWB may be useful in evaluating therapeutic response of NSCLC to chemotherapy.

Research Support This work was supported in part by a grant (R21 CA181885) from the National Cancer Institute of the National Institutes of Health.