Session Item

Durvalumab is an anti-PD-L1 immune checkpoint inhibitor that significantly improves clinical outcome after chemoradiotherapy (CRT) in patients with unresectable stage III NSCLC. However, metabolic changes of tumoral lesions and secondary lymphoid organs during durvalumab treatment are unknown until now. Therefore, we assessed metabolic patterns on 18F-FDG PET/CT in patients after durvalumab initiation versus patients undergoing CRT alone.

18F-FDG PET/CTs both before the initiation and after the completion of standard CRT were analyzed in 43 patients with inoperable stage III NSCLC. Thereof, 16 patients received additional durvalumab. Metabolic changes in tumor sites and secondary lymphoid organs were assessed and directly compared in the CRT alone and the durvalumab groups. Furthermore, scans were evaluated with regard to findings suspicious for immunotherapy-related adverse events (irAE), the readers being blinded for the durvalumab administration.

Before durvalumab administration, uptake characteristics were comparable in both groups, e.g. median tumoral SUVmax was 12.6 without vs. 13.4 with durvalumab (p = 0.452). With the initiation of durvalumab, however, uptake patterns in PET/CT diverged: A significantly higher reduction of tumoral uptake intensity was noted in the durvalumab group in comparison to the CRT alone group, e. g. median decrease of SUVmax –70.0% vs. –24.8%, respectively (p = 0.009). On the contrary, the spleen uptake increased after durvalumab initiation while it dropped in the group undergoing CRT alone (median +12.5% vs. –4.4%, p = 0.029). This was not the case for bone marrow uptake (+6.0% vs. –3.0, p = 0.353).

The median follow up time of the overall group was 28 months. Few events (progression/death) were noted in patients undergoing additional durvalumab treatment and the progression-free survival was significantly longer in those patients (median 19 vs. 6 months, p = 0.008).

PET/CT findings suggestive of an irAE (e.g. a sarcoid-like reaction) were present more often in patients undergoing durvalumab treatment compared to patients undergoing CRT alone (12/16 vs. 8/27 patients, p = 0.005).

Here, we present first preliminary data on the influence of durvalumab on 18F-FDG PET/CT findings in patients with unresectable stage III NSCLC undergoing chemoradiotherapy. Initiation of durvalumab consolidation after CRT leads to diverging metabolic patterns at tumor sites, but also alters splenic metabolism and leads to a significantly higher incidence of findings suggestive of irAE.