1104P - Early time-point ¹⁸F-FDG-PET/CT at week four (W4) as a prognostic biomarker of survival in metastatic melanoma (mM) patients (pts) on immunotherapy

Background

A considerable proportion of mM pts do not respond to immunotherapy with immune check-point inhibitors (ICI). There is a great need to develop non-invasive imaging biomarkers (IBM) to detect pts not responding to ICI. The aim of this study was to evaluate the role of an early time-point ¹⁸F-FDG-PET/CT at W4 as a prognostic biomarker of overall survival (OS) in mM pts on ICI.

Methods

In this prospective non-interventional, one-centre clinical study mM pts, receiving ICI, were regularly followed by ¹⁸F-FDG PET/CT. Pts were scanned at baseline, at W4 after ICI initiation, week sixteen (W16) and week 32 (W32). Tumour response to ICI at W4 was assessed using a modified EORTC criteria. Pts were first classified into 6 categories: complete response (CR), partial response (PR), stable disease (SD), progressive disease (PD), mixed response (MR), possible pseudoprogression (PP). The pts with PD were then classified into no clinical benefit group (no-CB), all others into clinical benefit group (CB). The primary end point was analysis of OS based on W4 ¹⁸F-FDG PET/CT response. Kaplan-Meier analysis was done to compare different categories and Pearson correlation was used to correlate prognostic value of W4 scan and level of serum LDH at the beginning of ICI treatment.

Results

Altogether, 71 pts were included. Median follow-up of pts was 30 months (95% CI = [23.1-34.1]). Three (4%) pts had only baseline scan due to rapid disease progression and death prior to W4 ¹⁸F-FDG-PET/CT. Fifty- one (72%) pts were classified into CB group and 17 (24%) into no-CB group. Twenty-three (32%) pts had elevated serum LDH. There was a statistically significant difference in median OS between CB group (mOS not reached; 95% CI = [18 - NA]) and no-CB group (mOS 6.3 months; 95% CI = [4.6-NA]), (p =. 001), and also in mOS between pts with normal level of LDH (mOS not reached, 95% CI = [18 - NA]) and elevated level of LDH (mOS 6.3 months; 95% CI = [3.8-NA]), (p =. 001). There was no correlation between tumour response at W4 and LDH level (r = -.34).

Conclusions

Evaluation of mM pts with early ¹⁸F-FDG-PET/CT at W4, treated with ICI, can serve as a prognostic IBM. It is independent from serum LDH level.

Clinical trial identification

NCT06207747.

Editorial acknowledgement

Legal entity responsible for the study

The authors.

Funding

Has not received any funding.

Disclosure

R. Jeraj: Non-Financial Interests, Institutional, Leadership Role: AIQ Solutions. All other authors have declared no conflicts of interest.