Sir Sam Neill says he is cancer-free and credits a groundbreaking new therapy for it.

The 78-year-old New Zealand actor, who lives in Central Otago, was diagnosed with stage three blood cancer four years ago.

"I've been living with a particular type of lymphoma. I was on chemotherapy and the pretty miserable business but it was keeping me alive," Neill told 7News.

"Then the chemo stopped working. I was at a loss and it looked like I was on the way out, which wasn't ideal, obviously."

Sir Sam ultimately underwent CAR T-cell therapy to train his immune cells to recognise and destroy cancer, and the results have been remarkable.

The actor - whose film credits include The Hunt For Red October, The Piano, The Dish and Jurassic Park - said: "I've just had a scan just now and there is no cancer in my body.

"That's an extraordinary thing.…