Supplementary Material for: Experience and Lessons Learned in the Treatment of Transforming Small Cell Neuroendocrine Carcinoma of the Prostate: A Case Report and Literature Review

<b><i>Introduction:</i></b> Small cell neuroendocrine carcinoma of the prostate (SCNECP) is a rare and highly malignant tumor that commonly transforms into conventional prostate adenocarcinoma (CPAC). Most of SCNECP cases cannot be detected and diagnosed early, and SCNECP is often diagnosed when there is liver and lung metastasis. Therefore, the early detection of the process from CPAC to SCNECP is crucial. <b><i>Case Report:</i></b> We present a case of a 73-year-old man who was initially admitted to our hospital with metastatic CPAC. He was administered goserelin acetate 3.6 mg combined with bicalutamide tablets (50 mg) once daily for endocrine therapy and docetaxel (100 mg) combined with prednisone (5 mg) twice a day. After treatment, the prostate-specific antigen (PSA) level decreased significantly, but the CEA, CA199, and CA125 levels began to increase progressively after a short decline. However, no solid tumor recurrence was observed in multiple reexaminations. It was not until 9 months after the elevation of tumor markers that multiple metastatic lesions appeared in the liver, which finally confirmed the diagnosis of metastatic SCNECP. After chemotherapy with etoposide 360 mg combined with carboplatin 200 mg, the tumor size was significantly reduced, and tumor markers decreased. However, the remission time was only 3 months. The patient’s liver metastases continued to grow, and CEA, CA199, and CA125 levels continued to increase. <b><i>Conclusion:</i></b> During CPAC treatment, PSA levels continued to decrease, whereas CEA, CA199, and CA125 levels continued to increase. This suggests the possibility of the transformation of CPAC into SCNECP.

**引言：** 前列腺小细胞神经内分泌癌（Small cell neuroendocrine carcinoma of the prostate, SCNECP）是一种罕见且恶性程度极高的肿瘤，常由常规前列腺腺癌（conventional prostate adenocarcinoma, CPAC）转化而来。多数前列腺小细胞神经内分泌癌病例难以实现早期检出与确诊，往往在出现肝、肺转移时方才得以诊断。因此，识别常规前列腺腺癌向前列腺小细胞神经内分泌癌转化的早期进程具有重要临床意义。

**病例报告：** 本文报告1例73岁男性患者，因转移性常规前列腺腺癌首次入院。患者接受醋酸戈舍瑞林3.6 mg联合比卡鲁胺片（50 mg）每日1次的内分泌治疗，同时予多西他赛（100 mg）联合泼尼松（5 mg）每日2次的化疗方案。治疗后，患者前列腺特异性抗原（prostate-specific antigen, PSA）水平显著下降，但癌胚抗原（CEA）、糖类抗原199（CA199）及糖类抗原125（CA125）水平在短暂回落之后开始进行性升高。多次复查均未观察到实体瘤复发征象，直至肿瘤标志物升高9个月后，患者肝脏出现多发转移性病灶，最终确诊为转移性前列腺小细胞神经内分泌癌。予依托泊苷360 mg联合卡铂200 mg化疗后，肿瘤体积显著缩小，肿瘤标志物水平下降，但缓解期仅为3个月。随后患者肝转移灶持续增大，CEA、CA199及CA125水平亦持续升高。

**结论：** 在常规前列腺腺癌治疗过程中，若前列腺特异性抗原水平持续下降，而癌胚抗原、糖类抗原199及糖类抗原125水平持续升高，需警惕常规前列腺腺癌向前列腺小细胞神经内分泌癌转化的可能性。