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. 2025 Aug 17;13(8):e70319.
doi: 10.1002/rcr2.70319. eCollection 2025 Aug.

Early Pseudoprogression After Tarlatamab in Small-Cell Lung Cancer: A Case Report

Yoshio Nakano  1 , Hiroka Serizawa  1 , Yuri Enomoto  1 , Yusuke Kuze  1 , Norio Okamoto  1 , Iwao Gohma  1
Affiliations

Early Pseudoprogression After Tarlatamab in Small-Cell Lung Cancer: A Case Report

Yoshio Nakano et al. Respirol Case Rep. .

Abstract

Pseudoprogression, a transient radiographic flare caused by immune infiltration, is common after immune-checkpoint inhibitors but has not been reported with tarlatamab, a bispecific T-cell engager approved for third-line small-cell lung cancer (SCLC). A 57-year-old woman with extensive-stage SCLC and syndrome of inappropriate antidiuretic hormone secretion (SIADH) received tarlatamab. Within hours, she developed bone pain; Day 7 imaging showed marked tumour swelling and pleural effusion despite negative cytology and rising serum sodium. Therapy continued. By Day 13, computed tomography demonstrated regression of thoracic and hepatic lesions and falling pro-gastrin-releasing peptide (pro-GRP). Early pseudoprogression and paraneoplastic biomarker improvement may predict efficacy.

Keywords: bispecific T‐cell engager therapy; pseudoprogression; small‐cell lung cancer; tarlatamab.

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Conflict of interest statement

The authors declare no conflicts of interest.

Figures

FIGURE 1
FIGURE 1
Serial chest radiographs before and after tarlatamab administration. (a) Baseline radiograph showing a left‐upper‐lobe mass without pleural effusion. (b) Day 7 after the first dose: Enlargement of the primary lesion and new left pleural effusion. (c) Day 12 after the first dose: The primary lesion is smaller than at baseline, and the pleural effusion has resolved.
FIGURE 2
FIGURE 2
Chest computed tomography (CT) images before and after tarlatamab treatment. (a) Baseline CT demonstrating a mediastinal‐side mass in the left upper lobe. (b) Baseline CT demonstrating multiple hepatic metastases. (c) Day 13 post‐treatment: Marked reduction of the primary left upper lobe lesion. (d) Day 13 post‐treatment: Regression of hepatic metastases.
FIGURE 3
FIGURE 3
Timeline of systemic therapy and serial pro‐GRP levels. The serum pro‐gastrin‐releasing peptide (pro‐GRP) concentration mirrored the disease course; levels declined rapidly to the normal range after initiation of tarlatamab.
See this image and copyright information in PMC

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