Cancer Worldview

Just as cancer knows no borders, efforts to prevent it must cross national boundaries to save millions upon millions of lives in the coming decades, experts agree.

Although cancer, diagnosed in some 10 million people around the world each year, is a global problem, “regrettably this is poorly recognized by a majority of governments,” Eduardo Cazap, MD, said recently in Chicago at the annual meeting of the American Society of Clinical Oncology. Cazap, chair of the society’s international affairs committee, led a session at the meeting titled “Primary Prevention in Global Oncology: What Can We Gain?”

Cancer deaths are expected to increase mainly in developing nations, Franco Cavalli, MD, said at the session. He noted that by 2020, three-quarters of cancer deaths will be in those countries, where poverty contributes to the incidence and deadliness of certain tumors.

Besides poverty, another problem is poorer nations’ growing adoption of bad health habits. “We know that almost half of the tumors could be prevented, since they are due to tobacco, diet and infection,” said Cavalli, of the Oncology Institute of Southern Switzerland and the International Union Against Cancer (UICC).

Targeting tobacco use alone has the potential to save perhaps a billion lives this century, explained Sir Richard Peto of the University of Oxford in England. Smoking is the main cause of cancer in the world, he said. “It is also the main cause of death in adult life in the world.”

While tobacco is largely associated with lung cancer, it also causes malignancies of the throat, mouth, pancreas, bladder, stomach, liver and kidney, among other sites. “It’s a common habit — about a billion people do it — and if you smoke throughout life then there’s about a 50 percent chance it will kill you,” Peto said.

The good news is that a global effort to get adults to quit now can greatly reduce death rates in the next few decades, and an effort to keep kids from taking up the habit will save more lives later on, he said. “These are complementary strategies, and for that we need serious implementation.”

Another vital area is breast cancer prevention, the No. 1 cause of cancer and cancer deaths among women worldwide, said Bernard Fisher, MD, of the University of Pittsburgh.

Fisher noted landmark research showing success of agents such as tamoxifen and raloxifene in preventing breast cancer. But these treatments currently are aimed at women 50 or older, he said, which translates to less than 21 percent of the world’s 3.28 billion females. He urged colleagues to consider extending the drugs’ use to younger women who are at high risk for breast cancer.

“It’s a common habit — about a billion people do it — and if you smoke throughout life then there’s about a 50 percent chance it will kill you.”

Vaccines — specifically targeting cervical cancer and liver cancer — are yet another way to reduce the worldwide reach of cancer, said Hakan Mellstedt, MD, PhD, of Karolinska University Hospital in Stockholm, Sweden.

Cervical cancer is the third most common cancer in women worldwide, resulting in some 190,000 deaths each year, he said. But many of those deaths are preventable. In nations where Pap smears are common, Mellstedt said, death rates from cervical cancer have dropped dramatically.

New vaccines targeting HPV, the human papillomavirus, can reduce the toll further. But getting it to girls around the world early enough, before they are sexually active and infected, is crucial. “Once they have the infection, this type of vaccine is not effective,” Mellstedt said.

Likewise, early protection against the hepatitis B virus, the most common cause of liver cancer worldwide, holds promise. Some 2 billion people are infected with hepatitis B, and more than 350 million have chronic infections.

Vaccination campaigns targeting newborns in countries such as Taiwan and Gambia have shown that hepatitis B infection rates can be reduced dramatically, Mellstedt said. Research in Taiwan has further shown that vaccination translates to lower rates of the most common type of liver cancer, hepatocellular carcinoma.

The threat of colon cancer, meanwhile, could be greatly reduced by widespread screening for (and removal of) precancerous polyps, and reduction in rates of obesity and inactivity, said Peter Greenwald, MD, DrPH.

Greenwald, of the National Cancer Institute, cited research showing a 75 to 90 percent drop in colorectal cancer rates through screening and polyp removal using colonoscopy. The problem is, people don’t like invasive colon exams, he added, expressing hope that a very reliable, noninvasive means of detecting polyps would soon be developed.

Inactivity and an unhealthy diet also must be priorities, he said. “We’ve got to affect our environment worldwide to reduce some of the cancer rates. … What we do in any country teaches us lessons for everyone.”

For more information about efforts to reduce cancer globally, see www.uicc.org.