Pseudoprogression Associated With T-cell Infiltration During Tarlatamab Therapy for Small-Cell Lung Cancer: A Case Report

TL;DR

This case report describes pseudoprogression in a small-cell lung cancer patient treated with tarlatamab, showing how T-cell infiltration can temporarily enlarge tumors.

Contribution

The study highlights blood test trends as potential indicators to distinguish pseudoprogression from true disease progression during tarlatamab therapy.

Findings

The patient experienced pseudoprogression due to T-cell infiltration during tarlatamab treatment.

Peripheral blood lymphocyte count decreased while interleukin-6 levels increased, suggesting T-cell accumulation in the tumor.

Blood test trends may help differentiate pseudoprogression from true disease progression.

Abstract

Tarlatamab is a bispecific T-cell engager immunotherapy that targets delta-like ligand 3 and CD3. We report a case of pseudoprogression (PsPD) in a patient with small-cell lung cancer treated with tarlatamab. Due to its mechanism, tarlatamab is known to induce T-cell infiltration into tumors. In PsPD, the tumor transiently enlarges because of massive T-cell accumulation within the tumor. In this case, the peripheral blood lymphocyte count decreased, and the interleukin-6 level was markedly elevated, which was thought to reflect T-cell accumulation in the tumor. These trends in the blood tests may be useful in easily differentiating PsPD from true progressive disease during tarlatamab treatment.

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