What happened, in summary

A 59-year-old man with a long smoking history presented with 2 months of hoarseness and shortness of breath. CT showed a 3.8 × 3.1 cm irregular mass in the posterior apical segment of the left upper lung, enlarged mediastinal and left hilar lymph nodes, and uneven thickening of the sigmoid colon wall. Blood work showed mild anemia, a positive fecal occult blood test, and markedly elevated tumor markers: CEA 212.53 ng/mL, CA 19-9 1111.54 U/mL, and CA 125 681.2 U/mL. CT-guided lung biopsy confirmed non-small cell lung cancer with SMARCA4 deletion. The lung tumor was CK-positive, CK7-positive, had Ki-67 greater than 40%, and showed loss of BRG-1. Colonoscopy found an obstructing annular sigmoid lesion. At first, the team could not determine whether the colon tumor was a separate primary cancer or metastasis. He received 3 cycles of albumin-bound paclitaxel 400 mg, carboplatin 400 mg, and camrelizumab 200 mg every 3 weeks, followed by intensity-modulated radiation therapy to the lung area, 60 Gy in 30 fractions. During radiation, hematochezia developed. The lung mass shrank, but the sigmoid tumor enlarged, so he underwent laparoscopic radical sigmoid colectomy with regional lymph-node dissection. Pathology showed poorly differentiated carcinoma in the sigmoid colon, and immunostaining confirmed metastatic sigmoid colon cancer from SMARCA4-deficient NSCLC rather than a primary colon cancer. After surgery, radiotherapy continued. Two months later, a left adrenal metastasis appeared, and treatment changed to gemcitabine, nedaplatin, bevacizumab, and camrelizumab. At latest follow-up, the cancer was responding, with no further recurrence or new metastasis reported.