Cancer survivors are at greater risk of developing another cancer and dying from it, a new study finds.
These new cancers can result from a genetic predisposition, from treatments such as radiation and chemotherapy used to fight the first cancer, as well as from unhealthy lifestyles such as smoking and obesity, according to researchers from the American Cancer Society.
Some of these factors can't be controlled, but others can, noted lead researcher Dr. Ahmedin Jemal, a senior vice president at the society.
"We can do a lot for smoking and overweight and obesity," he said. "We have to get primary care clinicians to do a more concerted effort to educate, or counsel, their patients."
Jemal added that screening smokers for breast, cervical, colon and lung cancer is essential.
Dr. Alice Police, regional director of breast surgery at Northwell Health Cancer Institute in Sleepy Hollow, N.Y., said not smoking and maintaining a healthy weight can go a long way in keeping a second cancer at bay.
"More and more data are showing that these things are particularly important in cancer patients," said Police, who was not part of the study. "Particularly in breast cancer, we have a ton of data showing that those things will help prevent the second breast cancer."
She regularly speaks to patients about the importance of diet, exercise and smoking cessation in cancer prevention.
"We're not as good at that in this country as they are in Europe and other countries," Police said. "We're still mostly a fee-for-service medical establishment, and prevention doesn't pay as a treatment does, and that's really a problem in the U.S."
Drawing from 12 cancer-tracking registries, the researchers collected data on more than 1.5 million Americans who beat cancer between 1992 and 2017.
Among the survivors, more than 156,000 had a second primary cancer, and more than 88,800 died from it.
Men had an 11% higher risk of developing a second cancer and a 45% higher risk of dying from it, compared with the general population, the study found.
Women had a 10% higher risk of developing a second cancer and a 33% higher risk of dying from it, researchers reported.
Men who survived laryngeal cancer and Hodgkin lymphoma were most likely to develop another cancer, and men who survived gallbladder cancerhad the greatest risk of dying from a second cancer.
Women who survived laryngeal and esophageal cancers had the greatest risk of developing another cancer. Women who survived laryngeal cancer had the greatest risk of dying from a second cancer, according to the study.
Researchers found a lot of variation between the specific types of first cancers and the types of second cancers.
Second cancers linked with smoking and obesity were most common. The risks of smoking-related second cancers were higher among those who had survived smoking-related first cancers.
Smoking-related second cancers -- including lung, urinary, bladder, oral and esophagus -- accounted for 26% to 45% of second cancers and cancer deaths.
By itself, lung cancer accounted for 31% to 33% of all deaths from second cancers, the researchers found.
They also found that survivors of obesity-related cancers had higher odds for developing obesity-related second cancers.
Four obesity-related cancers -- colon, pancreas, endometrial and liver -- made up 22% to 26% of all deaths from second cancers, the researchers said.
Second cancers can be deadly because they are often induced by radiation or chemotherapy, and patients are then resistant to those treatments, said Dr. Anthony D'Amico, a professor of radiation oncology at Harvard Medical School in Boston. He was not involved with the study.
"As a result, you only have surgery to use, so, all the more reason why screening and early detection is even more important," D'Amico said.
He urges patients who have had one cancer to change their lifestyle to ward off another.
"If you've had cancer and you've been successfully treated, get rid of the bad habits like smoking and a poor diet," D'Amico said.
If you had chemo or radiation, you need to be monitored so another cancer can be caught early, he said. "A lot of it is just related to the fact that the thing that caused the first cancer can cause another one," D'Amico noted.
Doctors and patients can't control genetic risks, but factors like smoking, alcohol use and poor diet can be modified, D'Amico said.
The findings were published Dec. 22 in the Journal of the American Medical Association.
For more on second cancers, see the American Cancer Society.
SOURCES: Ahmedin Jemal, DVM, PhD, senior vice president, data science, American Cancer Society; Anthony D'Amico, MD, PhD, professor, radiation oncology, Harvard Medical School, Boston; Alice Police, MD, Westchester regional director, breast surgery, Northwell Health Cancer Institute, Sleepy Hollow, N.Y.; Journal of the American Medical Association, Dec. 22, 2020