Disseminated Carcinomatosis of the Bone Marrow in Colorectal Cancer: A Case Series of Two Patients with Rapidly Fatal Outcomes.

INTRODUCTION: Disseminated carcinomatosis of the bone marrow (DCBM) is a rare but highly fatal complication in colorectal cancer (CRC) patients. Although previous reports have described favorable responses to urgent chemotherapy, we encountered 2 cases of CRC-associated DCBM with a devastating clinical course. Here, we present these cases and discuss current optimal management in light of the literature. CASE PRESENTATION: The first patient was a 69-year-old man with stage IIIC rectal cancer who underwent high anterior resection with lymph node dissection and partial ileal and bladder resection after chemoradiotherapy. Four months after the surgery, the patient was admitted with severe fatigue. The second patient was a 69-year-old man with sigmoid colon cancer who underwent laparoscopic sigmoid colectomy with regional lymph node dissection. Pathological examination revealed lymph node metastases and peritoneal dissemination, and the disease was classified as stage IVC. He received 20 cycles of mFOLFOX6 plus bevacizumab; however, the peritoneal dissemination gradually progressed. Two years after the initial diagnosis, he was hospitalized due to fever of unknown origin. Both patients presented with cytopenia and circulating immature hematopoietic cells on admission and were promptly diagnosed with DCBM through hematology consultation, whole-body imaging, and bone marrow biopsy. Despite urgent initiation of systemic chemotherapy combined with a molecular-targeted agent and therapy for disseminated intravascular coagulopathy (DIC), hematologic abnormalities remained refractory, and both patients died shortly after diagnosis. Of note, the first patient delayed hospitalization due to financial reasons, resulting in severe DIC, rapid disease progression, and death eight days after admission. CONCLUSIONS: This series emphasizes the extremely high mortality of CRC-associated DCBM and highlights the importance of earlier detection during routine follow-up and urgent intervention for oncological DIC, along with consideration of palliative care at the time of diagnosis. Further studies are needed to better understand its biology and optimal management.