Colon Cancer in Decline
In July, 1994, Cindy Stewart was playing first base in a Vancouver softball game when she stretched to catch a ball - and felt a sharp pain in her lower abdomen. When the pain persisted, Stewart checked into hospital and, after testing, was diagnosed with colon cancer. Because the cancer had spread, surgeons removed part of her bowel, one of her ovaries and four lymph nodes. After that, she endured a year of painful chemotherapy. But for Stewart, now 35, "the worst part of it all was the emotional trauma," stemming from the knowledge that only about one-fifth of patients operated on for advanced colon cancer are alive five years later. Even so, Stewart is determined to keep her life on course. A single parent with a 10-year-old daughter, Stewart, an accountant, is studying for a master's degree in business administration at the University of British Columbia. Every six months, she undergoes extensive tests and, so far, she appears to be free of cancer. "Things are looking pretty good," says Stewart. "But the fear never leaves - because I know the cancer can come back."
After lung cancer, tumors of the colon and rectum are the deadliest: this year, an estimated 16,400 Canadians will be diagnosed with colorectal cancer, and about 3,200 men and 2,700 women will die of the disease. Despite those bleak statistics, the mortality rate for colorectal cancer has steadily declined in North America during the past two decades. And improved diagnostic methods now make it possible to catch and treat the disease early on. Studies have shown that a simple test to detect tell-tale traces of blood in a patient's feces can save lives. And some specialists argue that colon cancer can be all but eliminated by screening patients over 40 with a colonoscope - a flexible tube inserted through the length of the colon - and removing pimple-like growth called polyps, thought to be precursors of the disease. Says Dr. Warren Rudd, a Toronto colorectal surgeon: "This is the only internal cancer that can be prevented before it starts." Rudd thinks everyone over 40 should undergo the uncomfortable procedure, although some medical experts argue that screening of the whole population would impose a prohibitive burden on the health-care system.
At the same time, scientists are steadily gaining insight into factors that can cause the genetic machinery in cells lining the colon's wall to run amok. In a major breakthrough, researchers at Baltimore's Johns Hopkins University last week reported a genetic flaw that may be responsible for one in every four colon cancer cases among Jews of European descent. The finding means that a simple blood test may soon be available to determine which of Canada's more than 300,000 Ashkenazi Jews are at risk. And "the broad implication," said Johns Hopkins' geneticist Steven Laken, "is that there are genes in other ethnic groups that do the same thing."
In fact, researchers estimate as many as half of all colorectal cancers may be caused by inherited defects. The rest arise because of carcinogens - substances inhaled or swallowed, or bred by the bacteria that thrive in the colon, or large intestine, the 4½-foot-long tube that runs from the end of the small intestine to the anus.
A range of symptoms - rectal bleeding, diarrhea, constipation and abdominal cramps - can be an early warning of colorectal cancer. To investigate, physicians conduct a colonoscopy and when polyps - which may already be cancerous - are spotted, they snare them with a wire loop, then send a jolt of electricity through the circuit to snip them off. Colonoscopies can also reveal cancer that has begun to spread, meaning surgery is probably the next step. If the cancer has not spread, surgery can be a cure in as many as 80 per cent of cases. Often, to be on the safe side, surgeons remove most or all of the rectum, a procedure that as recently as 20 years ago, doomed patients to the misery of carrying plastic colostomy bags to capture wastes. Now, thanks to improved medical technology, surgeons can usually stretch the remainder of the bowel and staple it to a remnant of the rectum. But if cancer has spread to the lymph nodes or to nearby organs before being detected, surgery is often impossible - and chemotherapy and radiation treatment can, at best, add months to patients' lives.
Physicians generally believe there are ways for most people to protect themselves against colorectal cancer - by insisting on regular rectal examinations, and by watching what they eat. Persuasive evidence suggests that a diet low in animal fats and high in fruit and vegetables can help fend off the disease. "There is almost certainly a role for diet," says Dr. Bernie McIntyre, a colorectal surgeon at Halifax's Queen Elizabeth II Health Sciences Centre, "and people who eat a lot of high-fat foods are probably at risk." While putting broccoli before burgers may not always be tempting to some, it could save lives.
Maclean's September 8, 1997