In search of the black sheep: is it bevacizumab or extended chemotherapy?

Portal vein embolization stimulates tumour growth in patients with colorectal cancer liver metastases

OBJECTIVES

Portal vein embolization (PVE) can facilitate the resection of previously unresectable colorectal cancer (CRC) liver metastases. Bevacizumab is being used increasingly in the treatment of metastatic CRC, although data regarding its effect on post-embolization liver regeneration and tumour growth are conflicting. The objective of this observational study was to assess the impact of pre-embolization bevacizumab on liver hypertrophy and tumour growth.

METHODS

Computed tomography scans before and 4 weeks after PVE were evaluated in patients who received perioperative chemotherapy with or without bevacizumab. Scans were compared with scans obtained in a control group in which no PVE was administered. Future liver remnant (FLR), total liver volume (TLV) and total tumour volume (TTV) were measured. Bevacizumab was discontinued ≥ 4 weeks before PVE.

RESULTS

A total of 109 patients and 11 control patients were included. Portal vein embolization induced a significant increase in TTV: the right lobe increased by 33.4% in PVE subjects but decreased by 34.8% in control subjects (P < 0.001), and the left lobe increased by 49.9% in PVE subjects and decreased by 33.2% in controls (P= 0.022). A total of 52.8% of the study group received bevacizumab and 47.2% did not. There was no statistical difference between the two chemotherapy groups in terms of tumour growth. Median FLR after PVE was similar in both groups (28.8% vs. 28.7%; P= 0.825).

CONCLUSIONS

Adequate liver regeneration was achieved in patients who underwent PVE. However, significant tumour progression was also observed post-embolization.

[Does bevacizumab have a protective effect on hepatotoxicity induced by chemotherapy?]

Although the prognosis of patients with colorectal liver metastases (CLM) has improved dramatically with oxaliplatin and irinotecan, the enthusiasm for the preoperative use of these cytotoxic agents is being tempered by concerns about their impact on the nontumoral liver parenchyma. Bevacizumab, an anti-angiogenic agent that specifically targets the vascular endothelial growth factor, exerts an antitumor effect by inhibiting the development of the vascular network that is promoted by the tumor and mandatory for its growth. Yet angiogenesis is also a physiologic event contributing to wound healing and tissue regeneration. To date, it is well documented that the use of bevacizumab in combination with cytotoxic agents greatly improves pathologic response. Also well described is the protective effect of bevacizumab against sinusoidal injuries induced by oxaliplatin-based chemotherapy. Up to now, no side effects related to the perioperative use of bevacizumab have been reported in the setting of liver resection for CLM, and bevacizumab was shown not to impair liver regeneration following portal vein embolization. The clinical consequences of the protective effect of bevacizumab against sinusoidal injuries are hard to evaluate as patient selection and preparation have improved and these improvements contribute greatly to the favorable outcomes following liver resection for CLM. Indeed, patient safety in the setting of hepatic resection for CLM mainly depends on a careful preoperative evaluation of liver volumes and a limited use of cytotoxic agents followed by a delay of at least 5 weeks before the surgery.