Increase of serum complement levels in cancer patients with progressing tumors.

Complement levels (CH50, C3, C4 and C1q) were determined in sera of 90 healthy subjects and 200 cancer patients. Complement levels of cancer patients were significantly higher than those of the healthy subjects, but there was a stage-linked increase of complement levels. Patients in remission had nearly normal complement levels, but patients with local tumor had increased complement levels, and a further increase was observed in patients with distant metastases. Treatment of these patients with radiotherapy or cytostatic drugs lowered the complement levels. At the terminal phase of the disease we also noted a drop in complement levels.