Introduction: Angiostatin and endostatin are endogenous inhibitors of angiogenesis with anticancer effects. After minimally invasive colorectal resection (MICR), blood levels of the proangiogenic factors vascular endothelial growth factor (VEGF) and angiopoetin 2 (Ang-2) are elevated for 2-4 weeks. Also, postoperative human plasma from weeks 2 and 3 after MICR has been shown to stimulate endothelial cell proliferation and migration, which are critical to angiogenesis. This proangiogenic state may stimulate tumor growth early after MICR. Surgery's impact on angiostatin and endostatin is unknown. This study's purpose is to determine perioperative plasma levels of these two proteins in colorectal cancer (CRC) patients undergoing MICR.
Methods: Endostatin levels were assessed in 34 CRC patients and angiostatin levels in 30 CRC patients. Blood samples were taken preoperatively and on postoperative day (POD) 1 and 3 in all patients; in a subset, samples were taken between POD 7 and 20. The late samples were bundled into 7-day blocks (POD 7-13, POD 14-20) and considered as single time points. Angiostatin and endostatin plasma levels were determined via enzyme-linked immunosorbent assay (ELISA) in duplicate. Wilcoxon signed-rank test and Student's t test were used to analyze endostatin and angiostatin data, respectively. Significance was set at P<0.0125 (after Bonferroni correction).
Results: There was a significant decrease in median plasma endostatin levels on POD 1, which returned to the preoperative level by POD 3. There was no significant difference between pre- and postoperative plasma angiostatin levels.
Conclusions: MICR has a very transient impact on plasma levels of endostatin and no impact on angiostatin during the first 21 days following surgery. Thus, angiostatin and endostatin do not likely contribute to or inhibit the persistent proangiogenic changes noted after MICR.