Increased thyroid uptake on 18F-FDG PET/CT is associated with the development of permanent hypothyroidism in stage IV melanoma patients treated with anti-PD-1 antibodies.

PURPOSE: To determine performances of 2-deoxy-2-(18F)fluoro-D-glucose (18F-FDG) positron emission tomography (PET) to detect the development of permanent thyroid dysfunction (PTD), and to evaluate the prognostic value of early increased thyroid uptake in stage IV melanoma patients treated with anti-programmed death 1 (anti-PD-1) antibodies. METHODS: Twenty-nine patients were retrospectively enrolled. PTD was defined as symptomatic thyroid disorder requiring long-term specific treatment. On the first PET performed during follow-up, maximal standardized uptake value of the thyroid (SUVmax-Th) and SUVmax-Th/SUVmax-blood-pool ratio (Th/B) were measured. Areas under ROC curves (AUC) of these parameters for the diagnostic of PTD were compared. Cutoff values were defined to maximize the Youden's index. Survival analyses were performed according to the Kaplan-Meier method and compared using the log-rank method between patients with and without enhanced thyroid uptake according to cutoff values defined with the Hothorn and Lausen method. RESULTS: Four patients presented PTD. Median SUVmax-Th and Th/B were, respectively, 2.11 and 1.00. The median follow-up period was 21.7 months. AUC were 1.0 (CI95% 0.88-1.0) for both parameters. Optimal cutoff values were, respectively, SUVmax-Th > 4.1 and Th/B > 2.0, both conferring sensitivities of 100% (CI95% 40-100%) and specificities of 100% (CI95% 86-100%). The median progression-free survival and overall survival were 11.3 months and 33.5 months, respectively. Using optimized cutoffs, there was no statistically significant difference of survival. CONCLUSION: SUVmax-Th > 4.1 and Th/B > 2.0 provided perfect diagnostic performances to detect patients that developed PTD. No significant survival difference was found between patients with and without increased thyroid uptake.

Prognostic impact of thyroid dysfunctions on progression-free survival in patients with metastatic melanoma treated with anti-PD-1 antibodies.

This study aimed to assess the prognostic value of thyroid dysfunctions in metastatic melanoma patients on anti-programmed death-1 (anti-PD-1). A total of 110 stage IV or inoperable stage III melanoma patients treated with anti-PD-1 alone or in association with anti-CTLA-4 (T-lymphocyte antigen-4) antibody from January 2015 to December 2017 at our institution were enrolled in this retrospective study. Median follow-up was 32.8 months. Transitory thyroid dysfunctions and permanent thyroid dysfunctions were distinguished. The main criterion was progression-free survival. Secondary criteria were best response and overall survival. Survival curves were compared with log-rank tests and a cox proportional hazard ratio model was used to adjust patients and melanoma characteristics. Thirty-eight (35%) thyroid dysfunctions were observed during the follow-up, including 25 transitory thyroid dysfunctions (23%) and 13 permanent thyroid dysfunctions (12%). Progression-free survival was longer in patients with thyroid dysfunction (18.1 months) than in patients without thyroid dysfunction (3.9 months, P = 0.0085). In multivariate analysis, thyroid dysfunctions were not an independent predictive factor for progression-free survival. Patients with thyroid dysfunction had a longer overall survival (P = 0.0021), and thyroid dysfunctions were associated with a lower mortality risk (hazard ratio = 0.40; P = 0.005). Best response was positively associated with thyroid dysfunctions (P = 0.048). Thyroid dysfunctions induced by anti-PD-1 were not an independent predictive factor for progression-free survival in metastatic melanoma patients but seemed associated with a better response and increased overall survival.

Biomarqueurs prédictifs de réponse aux inhibiteurs de points de contrôle immuns.

PREDICTIVE BIOMARKERS OF RESPONSE TO IMMUNE CHECKPOINT INHIBITORS: PD-1 checkpoint inhibitors are becoming the reference treatment for several types of cancers. Many patients show remarkable efficacy and low toxicity. However, some patients have a better outcome than others with PD-1 checkpoint inhibitors. So, it is crucial to identify biomarkers of response. We review here the available data of several potential biomarkers of efficacy. The expression of PD-L1, detected by immunohistochemistry on tumor cells and immune cells is a good predictive biomarker of response for some cancers; however, this method is not standardized, and there are different antibodies, different cut-off values, and different targets (tumor or microenvironment). Moreover, the expression of PD-L1 is dynamic and heterogeneous within the tumor: expression is discordant between primary tumor and metastasis or between biopsy and surgical specimen. Peripheral blood lymphocytes also can be informative, especially the baseline neutrophil to lymphocyte ratio which is easy to measure in daily practice. High rate of neoantigens is also associated with improved response. Therefore, mutation burden can be predictive of response and this explains why tumors with microsatellites instability have an enhanced response. Similarly, genetic signatures are linked with resistance or response to treatment. Gut microbiota is associated with improved antitumor immune response although the underlying mechanism is not well understood so far. Lastly, it seems that cytokines, mediators of immunity may play a role in the response to immunotherapy and so, constitute an interesting biomarker. Several potential biomarkers are identified but none is prospectively validated so far.