416P - Survival outcomes predicted by irAEs on 18F-FDG-PET in response to PD-1 antibody therapy in metastatic melanoma

Background

PD-1 antibody therapy has revolutionised the landscape of metastatic melanoma treatments and outcomes. The aim of our study is to investigate whether immune related adverse events (irAEs) or granulomatous/reactive nodal changes visible on ¹⁸F-FDG-PET during treatment with PD-1 antibody therapy for metastatic melanoma predicts improved overall survival.

Methods

Patient demographics, treatment regimes, toxicity profiles and ¹⁸F-FDG-PET scans were collected for patients who underwent treatment at Alfred Health in Melbourne, Victoria between 2015 and 2019 for advanced melanoma. Data were extracted from each patient’s electronic medical record. Patients were included if they were treated with 1^stline PD-1 antibody +/- CTLA-4 antibody therapy for unresectable stage III or stage IV metastatic cutaneous melanoma. Patients were excluded if an ¹⁸F-FDG-PET was not performed both during and prior to commencement of immunotherapy. Two blinded-nuclear medicine physicians reviewed ¹⁸F-FDG-PET imaging at baseline and following immunotherapy. The review criteria included granulomatous/reactive changes and PET detected irAEs. Clinically reported irAE were also collected. Statistical analysis was performed using IBM SPSS software.

Results

A total of 103 patients (68% male) met the inclusion criteria for the study. The largest proportion of individuals had M1c disease (26.2%) followed by unresectable stage III (25.2%), M1b (21.4%), M1a (16.5%) and M1d (10.7%) respectively. Most individuals received single agent anti-PD-1 (71.6%) whereas a smaller proportion received combination therapy with CTLA4 antibody therapy (28.4%). The median follow up period was 3.6 years. Patients with irAEs visible on ¹⁸F-FDG-PET during treatment had improved survival (p=0.004), this remained significant after adjusting for age, gender, stage and baseline LDH (p=0.03). Granulomatous/reactive nodal changes visible on ¹⁸F-FDG-PET did not have any significant impact on survival outcomes (p=0.74) nor did clinically reported irAEs (p=0.60).

Conclusions

This study demonstrates that irAEs visible on ¹⁸F-FDG-PET during PD-1 antibody therapy for metastatic melanoma predicts improved overall survival.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

The authors.

Funding

Has not received any funding.

Disclosure

All authors have declared no conflicts of interest.