TORONTO – The cancer that took the life of former Toronto mayor Rob Ford is among the rarest and most challenging to treat, says a doctor who specializes in a class of tumours called sarcomas.
Known as a pleomorphic liposarcoma, it belongs to a large group of malignancies called soft-tissue sarcomas, which arise in such tissues as muscle, tendons, blood vessels and fat.
“It’s rare to have a highly successful outcome with a pleomorphic liposarcoma once it’s spread,” said Dr. Brian Van Tine, a medical oncologist at Washington University in St. Louis.
There are four or five different types of liposarcoma, all of which arise in fat cells. While they can occur in almost any part of the body, tumours most commonly develop in the arms, legs and abdominal cavity.
Pleomorphic tumours are the rarest form of liposarcoma, and can often be highly aggressive. Pleomorphic means all the cancerous cells within the tumour have varying shapes and sizes when viewed under a microscope.
Ford, 46, was diagnosed in September 2014 with two tumours — a large one in his abdomen and a much smaller one in his buttocks — and underwent a combination of surgery, radiation and chemotherapy.
The treatments shrank his original tumours, but last November it was discovered that the cancer had come back in the form of two new tumours on his bladder.
The Toronto city councillor resumed chemotherapy, but recently got involved in an innovative program in which bits of his tumour were being grown in specially bred lab mice. The goal of the experimental program is to test different drugs on the rodents to see which ones might be able to put an individual patient’s cancer into remission, without exposing them to an ineffective agent.
Van Tine said there are about 100 different kinds of sarcoma, which represent about one per cent of all cancers; liposarcomas make up about 20 per cent of that one per cent, and cases of pleomorphic liposarcoma account for a fifth of those — making this kind of cancer extremely rare.
The Canadian Cancer Society doesn’t have separate statistics on liposarcoma. But overall, 1,175 Canadians were diagnosed with soft-tissue sarcomas in 2010, the most recent year for which statistics are available, and about 470 died of the disease.
While the cause of liposarcomas is not known, risk factors include being exposed to certain types of chemicals and radiation or having a weakened immune system. There is no scientific evidence linking liposarcomas to the use of alcohol or tobacco, nor is obesity a known risk factor.
Liposarcomas can occur at any age, but are most common in adults over age 50. Recurrences of tumours following treatment are not uncommon. Currently, the five-year survival rate for pleomorphic liposarcoma is about 56 per cent.
“Depending on where it arises and how big a tumour is before you catch it the first time, the challenges can be immense,” Van Tine said of trying to successfully treat the cancer. “I think the number one challenge is the lack of research in rare tumours and funding for research in rare tumours.”
Although there has been some progress in the field — two new drugs that don’t cure but can extend life for up to 14-16 months in some patients were approved for use last year — there’s still “no real game-changer,” he said.
Researchers and clinicians are now pinning their hopes on ongoing trials of “immunotherapy” drugs, which are aimed at revving up the body’s immune system to destroy cancer cells.
Van Tine said immunotherapy drugs used for melanoma skin cancer and lung cancer are now being tested in sarcoma patients.
“In the liposarcoma field, it will be interesting to see if immunotherapy is active.”