Stage III-IV thymic squamous cell carcinoma in complete pathological remission achieved with thymic cancer resection after immunotherapy combined with chemotherapeutic conversion therapy: a report of two cases from real-world data.

Background: Thymic carcinoma, a rare malignancy in the mediastinum, currently lacks standardized treatment options. Although surgery remains a crucial component among traditional therapeutic approaches, the potential benefits of radiotherapy and chemotherapy remain controversial. Nevertheless, a substantial number of patients are diagnosed with advanced tumor growth, posing challenges for achieving complete resection through surgical intervention and resulting in a poor prognosis. In light of the promising antitumor effects demonstrated by immunotherapy in various prevalent cancers, certain studies have shown favorable efficacy in advanced or recurrent thymic cancer cases. However, the incidence of adverse effects induced by immunotherapy in thymic cancer is notably higher compared to other tumor types, with severe and fatal complications being particularly significant. Consequently, there is an urgent need to address the crucial issue of patient selection for immunotherapy in thymic cancer. Case Description: In this study, we report on the treatment with programmed cell death protein 1 (PD-1) inhibitor therapy combined with chemotherapy conversion therapy for two patients diagnosed with stage III-IV thymic squamous cell carcinoma according to the Masaoka-Koga staging system. The aim of this study was to assess the effectiveness and safety of PD-1 inhibitor combined with chemotherapy conversion therapy in patients with thymic squamous cell carcinoma. Two patients in this cohort, one with stage III and another with stage IV disease, were deemed ineligible for upfront surgical resection. Puncture pathology confirmed the diagnosis of thymic squamous cell carcinoma. Both patients underwent transformation therapy using a combination of PD-1 inhibitors and chemotherapy. Tumor shrinkage was observed in both patients, enabling successful completion of surgery. Postoperative pathology revealed no residual tumor cells, indicating complete pathological remission. Notably, none of the patients experienced grade 3 or higher immunotherapy-related adverse reactions following immunotherapy. Conclusions: A combination of PD-1 inhibitors and chemotherapy followed by surgery demonstrated improved efficacy and enhanced safety for treating patients with Masaoka-Koga stage III-IV thymic squamous carcinoma and represents a potential novel therapeutic alternative for this disease.