Response assessment in non-small cell cancer immunotherapy: Initial experience in utilizing FDG PET/CT and PD-1 blocker nivolumab

Background Most NSCLC patients need systemic treatment. Immunotherapy is now current standard in second and first line treatment. In all pivotal studies staging was performed using conventional CT-scans. PET-CT based treatment monitoring is on the contrary recommended in NSCLC guidelines. This investigation aims at describing of benefits, challenges and possible pitfalls using PET/CT based monitoring for lung cancer during immunotherapy.

Patients and Methods We analysed 11 NSCLC patients treated with nivolumab at a German tertiary care lung cancer between 2015 and 2016. All patients received at least 2 follow-up PET-CTs. Evaluation of response was based on both RECIST and PERCIST criteria.

Results In 7 out of 11 cases, the RECIST and PERCIST results concurred, but two patients with initial stable disease regarding RECIST were reclassified as progressive metabolic disease based on PERCIST criteria.

Additionally, we identified one case of pseudo-progression using PERCIST criteria in contrast to stable disease using RECIST criteria and one case showing an early and durable response to nivolumab treatment using RECIST, despite a highly hypermetabolic mediastinal lymphnode metastasis.

Conclusion The findings indicate that the PERCIST-based evaluation could identify progressive disease earlier. Early identification of non-responders could lead to prevention of over-treatment and to an early switch to a more effective therapy.