Artificial blood vessels were made with either expanded polytetrafluoroethylene (ePTFE, a flexible teflon pipe) or with Tissue Engineered Vascular Grafts (TEVGs, basically a lab grown tissue using patient own cell).
This kind of surgery commonly used as heart bypass, vascular trauma, or in this case replacing the vessels due to cancer.
It came with a risk of trombosis (blood clot), fibrosis (thicken) which led to aneurysm (ballooning, and then burst), body rejection, and infection. Coupled with success rate as low as 20-30% in one year (depends on diameter size), the male doctor have rights to be worried.