We aimed to investigate, whether 18F-2-fluoro-2-desoxy-D-glucose positron emission tomography/computed tomography (FDG-PET/CT) scans performed at baseline (time point 0; TP 0) and three months after initiation of
immunotherapy (time point 1; TP 1) can be used on a
metastasis- and patient-level to predict the response to
immune-checkpoint inhibition using FDG-PET/CT six months
after treatment start (time point 2; TP 2) in metastatic
melanoma patients. This single-center retrospective study considered metastatic
melanoma patients treated with
immune checkpoint inhibition from TP 0 to TP 2. An analysis on a
metastasis- and patient-level was carried out.
Tumor volume, standardized uptake values SUV (mean, maximum, and peak), metabolic
tumor volume MTV and total lesion glycolysis TLG of each included
metastasis were recorded at each time point, respectively TP 0, TP 1 and TP 2. Total
tumor volume, total metabolic
tumor volume and total lesion glycolysis per patient were also calculated at TP 0, TP 1 and TP 2. Treatment response was assessed at
metastasis- and patient-level based on FDG-PET/CT scans at TP 2. 612
melanoma metastases in 111 patients were included. The analysis on a
metastasis-level showed that metastatic SUVpeak at TP 1 and volume variation between TP 0 and TP 1 were the strongest negative predictive
biomarkers for response. However, at TP 0, metastatic SUVmean and SUVpeak indicated a low negative prediction power, whereas initial metastatic volume was not a predictive
biomarker. Also,
melanoma metastases located in bone structures had a negative influence on the outcome at TP 2, particularly in women. The analysis on a patient-level showed, that total
tumor volume, total metastatic
tumor volume and total lesion glycolysis of all
metastases three months
after treatment initiation were strong negative predictive
biomarkers for response to
immunotherapy six months after initiation. Age and female sex were also found to be negative predictive
biomarkers with lower predictive power. Interestingly, total
tumor volume at TP 0 and number of
metastases at TP 0 as well as the occurrence of early immune-related adverse events between TP 0 and TP 2 did not have any predictive value for early treatment response. FDG-PET/CT performed for treatment response assessment three months after initiation of
immune checkpoint inhibition in metastatic
melanoma patients can also be used to predict early response to treatment. On a
metastasis-level SUV peak and volume variation of
metastases are strong outcome predictive
biomarkers. On a patient-level total
tumor volume and semiquantitative parameters such as total metabolic
tumor volume MTV and total lesion glycolysis TLG of all
metastases are promising outcome predictive
biomarkers. Also, early complete response on a
metastasis- and patient-level seems to be predictive for lasting complete response.