In patients with advanced melanoma, total metabolic tumor volume (TMTV) changes on 18-fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) 2 to 4 months after the start of therapy with pembrolizumab may predict long-term response and survival, according to a study in published in Current Oncology.

The study authors investigated whether changes in TMTV assessed with early on-treatment FDG-PET/CT affected outcomes in patients with advanced melanoma who were treated with pembrolizumab at the University Hospital of Brussels in Brussels, Belgium. They calculated the TMTV and compared the changes with survival parameters.

A total of 77 patients (median age, 66 years [range, 31-98]; 55.8% men) had at least 1 follow-up imaging examination. At 2 to 4 months, 36 patients had follow-up imaging, and at 5 to 6 months, 21 patients had follow-up imaging and were included in the analysis.

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By March 29, 2020, 38 of the 77 patients had died (median overall survival [OS] 168.4 weeks [95% CI, 62.0-275.0]). The median follow-up was 117.9 weeks (range 5.71-294.86), and the median progressive-free survival (PFS) was 28.4 weeks (95% CI, 14.6-42.2).

TMTV in the first follow-up FDG-PET/CT at 2 to 4 months was compared with TMTV at baseline, and the change was subdivided into 2 categories: stable/decreased TMTV (26 patients, 72.2%) and increased TMTV (10 patients, 27.8%). The median PFS in the stable/decreased-TMTV group was 203.1 weeks (95% CI, 159.7-246.5), and the median PFS in the increased-TMTV group was 85.3 weeks (95% CI, 33.0-137.5) (hazard ratio [HR] 5.5; P =.019). Median OS was 258.6 weeks (95% CI, 232.9-284.2) in the stable/decreased-TMTV group and 128.7 weeks in the increased TMTV group (95% CI, 76.2-181.1) (HR 10.5; P =.001).

Among the 21 patients with a follow-up FDG-PET/CT at 5 to 6 months, 18 (85.7%) of the patients had a stable/decreased TMTV, and 3 (14.3%) of the patients had an increased TMTV. The median PFS in the stable/decreased-TMTV group was 224.3 weeks (95% CI, 184.7-263.8) compared with 114.8 weeks (95% CI, 32.2-197.4) in the increased-TMTV group (HR 0.8; P =.364). The median OS in the stable/decreased-TMTV group was 243.7 weeks (95% CI, 211.3-276.0) compared with 158.0 weeks (95% CI, 80.6-235.2) in the increased-TMTV group (HR 1.2; P =.267)

The investigators noted their study’s relatively small population. Also, the retrospective design and the fact that the results of FDG-PET/CT examination affected the clinician’s decision whether to continue therapy led to significant bias, they added.

“…we found that TMTV change on follow-up FDG-PET/CT 2-4 months after baseline provides useful information to the clinician on PFS and OS, which could support the decision whether or not to continue treatment with pembrolizumab in patients with advanced melanoma,” the researchers concluded.

Disclosures: Several study authors declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.


Vermeulen S, Awada G, Keyaerts M, Neyns B, Everaert H. Early reassessment of total metabolic tumor volume on FDG-PET/CT in advanced melanoma patients treated with pembrolizumab predicts long-term outcome. Curr Oncol. 2021;28(3):1630-1640. doi:10.3390/curroncol28030152