The influence of metastatic patterns and tumor load on therapeutic efficacy of immunotherapy in patients with metastatic melanoma as determined by quantitative PET-parameters using [¹⁸F]-fluorodeoxyglucose PET/computed tomography

Abstract

The introduction of immunotherapy was a revolution in the treatment of metastatic melanoma. Nevertheless, there are only few clinical parameters to predict response to immunotherapy. The purpose of this study was to identify metastatic patterns that can predict response by using noninvasive ¹⁸F-FDG PET/CT imaging. In 93 immunotherapy-treated patients, total metabolic tumor volume (MTV) was measured before and after treatment. The differences were compared to quantify therapy response. Patients were divided into seven subgroups regarding the affected organ systems. The results as well as clinical factors were evaluated in multivariate analyses. No subgroup of metastatic patterns had a significant difference in response rates, but with a trend towards poorer response regarding osseous and hepatic metastases. Osseous metastases presented with significant lower disease-specific survival (DSS) (P = 0.001). Sole lymph node metastases were the only subgroup with MTV reduction and with significant higher DSS (57.6 months; P = 0.033). Patients, who ever developed brain metastases, showed a high progression of MTV of 201 ml (P = 0.583) and poor DSS of 49.7 months (P = 0.077). Lower numbers of affected organs indicated significantly higher DSS (hazard ratio, 1.346; P = 0.006). Osseous metastases represented a negative predictive factor for response to immunotherapy and survival. Cerebral metastases, especially when nonresponsive to immunotherapy, predicted poor survival and high increase of MTV. A high number of affected organ systems was identified as a negative factor for response and survival. Patients with only lymph node metastases showed a better response and survival.