A graft-versus-colonic cancer effect of allogeneic stem cell transplantation.

Allogeneic stem cell transplantation (ASCT) has proved to have an important immune-mediated anti-tumour effect in patients with haematologic malignancies. There is also evidence of such an effect in patients with malignant tumours. We studied this effect of ASCT in a patient with colorectal cancer. A 77-year-old man having a primarily resected colonic cancer with disseminated lymph node involvement received ASCT from his HLA-identical sibling as the only treatment. Mixed haematopoietic chimerism was monitored using PCR-amplification of variable number tandem repeats and tumour size, assessed by repeated CT scans. Recipient leucocytes were gradually replaced by donor cells for 1 month. Continuous resolution of lymph node metastases was seen together with clinical graft-versus-host disease (GVHD). The patient died of pneumonia and cardiac insufficiency 4 months after transplantation. At autopsy, most of the metastases were necrotic, with few remaining tumour cells. Clinical and histopathological postmortem results showed a graft-versus-colorectal cancer effect.