The Cancer SellThis film came about because Sarah Macdonald wanted to find out more, to investigate the alternative cancer treatments and the clinics behind them.

At first it seemed easy enough. The facilities promote their services through glossy brochures and online video testimonials, such as one from a woman called Lorraine Weaver, who describes how she reacted to suggestions for conventional medical treatment for lung cancer:

"They said they were going to do chemo and radiation and I said I don't think so. I walked out and called my niece and she said you go to Oasis of Hope... and I came down and I was cured and I thank God every day, don't ever give up hope."

She found that this kind of statement was by no means unusual. The clinics often claim survival rates that far outweigh anything a conventional oncologist could offer - a complete cure when all else has failed.

When you have just been told that there is nothing else conventional medicine can do for you, it is easy to understand the attraction. So you abandon rational thought, phone the travel agent and find yourself in Los Angeles about to take a bus tour around the Tijuana clinics.

Watch the full documentary now