Rising tobacco use in developing countries is believed to be a huge reason for the shift, particularly in China and India, where 40 percent of the world's smokers now live.
So is better diagnosing of cancer, along with the downward trend in infectious diseases that used to be the world's leading killers.
Cancer diagnoses around the world have steadily been rising and are expected to hit 12 million this year. Global cancer deaths are expected to reach 7 million, according to the new report by the World Health Organization.
An annual rise of 1 percent in cases and deaths is expected - with even larger increases in China, Russia and India. That means new cancer cases will likely mushroom to 27 million annually by 2030, with deaths hitting 17 million.
Underlying all this is an expected expansion of the world's population - there will be more people around to get cancer.
By 2030, there could be 75 million people living with cancer around the world, a number that many health care systems are not equipped to handle.
"This is going to present an amazing problem at every level in every society worldwide," said Peter Boyle, director of the WHO's International Agency for Research on Cancer.
Boyle spoke at a news conference with officials from the American Cancer Society, the Lance Armstrong Foundation, Susan G. Komen for the Cure and the National Cancer Institute of Mexico.
The "unprecedented" gathering of organizations is an attempt to draw attention to the global threat of cancer, which isn't recognized as a major, growing health problem in some developing countries.
"Where you live shouldn't determine whether you live," said Hala Moddelmog, Komen's chief executive.
The organizations are calling on governments to act, asking the U.S. to help fund cervical cancer vaccinations and to ratify an international tobacco control treaty.
Concerned about smoking's impact on cancer rates in developing countries in the decades to come, the American Cancer Society also announced it will provide a smoking cessation counseling service in India.
"If we take action, we can keep the numbers from going where they would otherwise go," said John Seffrin, the cancer society's chief executive officer.
Other groups are also voicing support for more action.
"Cancer is one of the greatest untold health crises of the developing world," said Dr. Douglas Blayney, president-elect of the American Society of Clinical Oncology.
"Few are aware that cancer already kills more people in poor countries than HIV, malaria and tuberculosis combined. And if current smoking trends continue, the problem will get significantly worse," he said in a written statement.
On the Net:
The WHO's IARC: http://www.iarc.fr
The American Cancer Society: http://www.cancer.org