A case of oxaliplatin-induced immune thrombocytopenia followed by complete remission of metastatic colon cancer

An 87-year-old male underwent laparoscopic left hemicolectomy for adenocarcinoma of the descending colon in December 2021. Lung metastasis was found in the left upper lobe 6 months postoperatively, and it increased in size after 9 months from the surgery. S-1 plus oxaliplatin (SOX) was started in October 2022. The lung metastasis was shrinking within 23 cycles of SOX therapy. The 24th cycle of SOX (only oxaliplatin) was administrated in April 2024, the catheter of venous infusion line of right forearm was removed after finishing the infusion, however bleeding did not stop. The platelet count was rapidly dropped into 2,000/μl from 131,000/μl (pretreatment) within 7 hours and hemoglobin levels decreased from 10.9 to 8.9 in the same period, furthermore, dropped into 6.2 g/dl in next 24 hours. PA-IgG was significantly high (204.0 ng/107 cells; normal < 30.2). Transfusion of platelet, red blood cell concentrate, steroid pulse therapy, antibiotic treatment with multiple agents and non-invasive positive pressure ventilation (NPPV with oxygen were performed. As a result, the patient’s platelet count was increased and his DIC score was decreased to 3 points (normal range) in April 2024. The patient’s general condition gradually improved, and he was discharged from hospital on the 35th day of hospitalization. CT scan after discharge showed complete remission of the lung metastasis. Possible mechanisms and approach to treatment are discussed.