Convincing people to eat healthy, exercise and quit smoking could drastically cut back on many preventable cancers, and a host of environmental factors that may lead to cancer have yet to be solved by science, experts say.
Still, researchers gathered at the American Society of Clinical Oncology annual conference here said there is plenty of cause for optimism.
This year's event, ASCO's 50th, brings together 30,000 doctors, researchers and pharmaceutical agents from around the world.
"Scientifically the field of oncology has never been more exciting," said Clifford Hudis, president of ASCO.
He cited new targeted therapies that take aim at the cellular functions of tumors, leading to progress against some difficult to treat cancers.
Also, immunotherapy is an exciting field that uses a patient's own immune system to attack tumors, and is showing promise against melanoma, leukemia, and a handful of other cancers.
"We have made incredible progress in 50 years," said Jyoti Patel, a cancer specialist at Northwestern University.
"What has been very exciting in the past several decades is the understanding of the biology of cancer, an effort of working together to catalogue the make-up and the molecular aberrations that distinguish cancer," Patel told AFP.
"In 2014 there will be almost 14 million cancer survivors in the US, and that number is expected to grow twofold over the next decades."
The death rate from cancer has dropped about 1.5 percent annually over the past decade, and a person diagnosed with cancer today has a higher than 66 percent chance of being alive in five years, according to US government statistics.
"The scientific breakthroughs in cancer are occurring at a breathtaking pace and are being translating into new drugs and devices that benefit patients more quickly than ever before," said Richard Schilsky, chief medical officer of ASCO.
However, he warned that this progress is in jeopardy due to a shortage of research funds, particularly from the National Institutes of Health, the largest government funder of US scientific research wich in 2013 had a budget of 28.9 billion dollars.
"The NIH budget has been flat for more than a decade and when adjusted for inflation... is nearly 25 percent lower today than in 2003," he said.
Hudis agreed that more government funding is needed.
"The nation's continued investment is critical if we are to make further progress against cancer and accelerated the progress already under way," said Hudis.
- Risk factors -
He also called for more focus on addressing both environmental and behavioral risk factors that drive up the cancer burden in the United States and around the world.
"While tobacco has long been the leading risk factor for cancer, obesity is a growing problem not only for the US but worldwide," he said.
"Obesity is overtaking tobacco, at least in the US, as the leading modifiable risk factor for multiple cancers," he said, mentioning colon and prostate cancer among the diseases susceptible to weight and eating habits.
A recent study in The Lancet found that one third of the world was overweight or obese.
"About two-thirds of cancers could be avoided if we changed our lifestyle, our diet and our sun exposure," said Patel.
She also urged more widespread vaccination against human papillomavirus (HPV) which can cause cancers of the cervix, anus, penis, head, neck and throat -- as well as improved vaccination against hepatitis which can lead to liver cancer.
Smoking also remains a top cause of cancer.
"So we need better education and stricter regulations for the tobacco industry," Patel said.