SMARCA4-deficient undifferentiated thoracic tumor: a case report and literature review

SMARCA4-deficient undifferentiated thoracic tumor (SMARCA4-UT) are very aggressive high-grade malignant tumors associated with poor prognosis. It is typically diagnosed at an advanced stage. Response to conventional therapeutic approaches is particularly poor and there is no specific targeted drug for this mutation site. Currently, there are no guidelines regarding the standard treatment for this disease.

In November 2021, a 71-year-old Chinese male was diagnosed with metastatic SMARCA4-UT in liver and brain. Molecular analysis showed a TP53 mutation in exon 10 and a programmed death-ligand 1 (PD-L1) tumor proportion score (TPS) of <1%. From January 2022, the patient received a combination of camrelizumab, bevacizumab, pemetrexed, and carboplatin for four cycles, followed by camrelizumab, bevacizumab, and pemetrexed maintenance therapy for 31 cycles. The last treatment was on June 25, 2024. Imaging follow-up revealed a tumor reduction of approximately 50% as the best response. To date, the progression-free survival (PFS) has surpassed 32 months.

To our knowledge, this is the first patient with SMARCA4-UT treated with this regimen. The first-line combined regimen containing immunotherapy plus antiangiogenic therapy and chemotherapy demonstrated durable treatment response in this case. This may represent a novel treatment option for this group of patients. Prospective studies will be required to validate the efficacy and safety of this therapy.