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Cancer patients used to be told to go home and take care of themselves without too many specifics for life after treatment. Now, as soon as they’re feeling strong enough, they’re advised to mind their lifestyle: lace up their sneakers, eat healthy, watch their weight and avoid tobacco and excess alcohol.

Roughly a third of cancers are considered preventable and the lifestyle recommended to help avoid them is the focus of ongoing research to help cancer survivors live healthier and, perhaps, longer.

Healthy behaviors may be especially important for someone who has had cancer. “They can not only be potentially helpful in preventing cancer from being there in the first place, but . . . they may be powerful tools in preventing recurrence,” said Jennifer Ligibel, a senior physician at Dana-Farber Cancer Institute in Boston. “We’re hoping that these types of things can improve survival rates in people who’ve had early cancers.”

Cancer survivors often need a tailored lifestyle program because side effects from their treatments can make it harder for them even to put on their shoes and go outside, Ligibel said.

About 14.5 million Americans are living with a history of cancer, and those ranks are expected to reach 19 million by 2024, according to the American Cancer Society. More than two-thirds of U.S. cancer survivors live five years beyond diagnosis, up from half in the 1970s and a third in the 1950s.

“We’re getting better at catching it earlier and treating it,” said Kathryn H. Schmitz, director of the exercise medicine unit at the University of Pennsylvania’s Perelman School of Medicine.

While advances in battling cancer have grabbed the spotlight, post-treatment life has gotten much less attention, as detailed more than a decade ago in an Institute of Medicine report called “From Cancer Patient to Cancer Survivor: Lost in Transition.” A patient who turns into a survivor faces many challenges: physical and psychological effects of treatment, including fatigue, numbness, pain and anxiety; and additional disease. Some effects can appear months or years later.

Survivors also live with the possibility of a recurrence or of developing a different form of cancer. Nearly 1 in 5 cancers are a second diagnosis, according to the National Cancer Institute.

Lifestyle and well-being

A healthy lifestyle can help survivors feel better and cope with the changes that cancer brings.

“Cancer forever changes an individual — not because of the cancer itself; usually, it’s because of the treatment,” Schmitz said.

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Fatigue is the most common side effect of many cancer therapies, and some fatigue can persist for months or even years, according to the National Cancer Institute. More than 100 studies have shown that survivors who participate in exercise programs reduce their fatigue levels, said Ligibel, who is also an assistant professor at Harvard Medical School.

Weight loss and exercise improve quality of life and the functioning of the body for cancer survivors, she said.

Studies suggest that exercise may help cognitive functioning in cancer survivors. After treatment some can feel a general mental fog in attention, thinking or short-term memory.

People with early forms of many cancers, including breast and prostate, may have a higher risk of dying of heart disease or other disorders than of cancer, Ligibel said. Cancer and heart disease share many risk factors, such as obesity and inactivity. Cancer treatments can also cause people to gain weight and become less active, increasing the risk of heart disease and diabetes. Finally, some cancer treatments can have a direct adverse impact on the heart. For all of these reasons, physical activity and nutrition are very important for survivors.

“I think sometimes we get lost in the fact that someone has had cancer and forget about their competing risks,” she said.

Associations with disease

Being fit and eating well may help bolster energy levels and address some of the metabolic and biological factors in survivors that can create conditions for developing cancer and other diseases down the road, said Linda Nebeling, deputy associate director of behavioral research at the National Cancer Institute.

Over the past five years, research has increasingly focused on energy balance, a concept linking exercise, diet and weight: Calories eaten should be balanced by calories burned in exercise, thereby avoiding turning extra calories into excess weight.

Large studies have shown a relationship between energy balance and risk of cancer recurrence and death in people who have had breast, prostate, colon and perhaps other cancers, Ligibel wrote in a review article in the Journal of Clinical Oncology. Although cause and effect has not been established, data reveal that obesity is linked to an increased risk of breast cancer recurrence and breast-cancer-related death in women diagnosed with early-stage breast cancer, Ligibel said. Obesity has also been linked to recurrences of colon and rectal cancers.

Ligibel said that people who are more physically active after a diagnosis of breast, colon or prostate cancer appear to have a lower risk of recurrence than inactive survivors of those cancers.

Regarding diet, there is no “magic food” that promotes survival, said Cheryl Rock, a professor of family medicine and public health at the University of California at San Diego School of Medicine. Many researchers examine patterns of eating because foods and nutrients are not consumed in a vacuum. Dietary patterns that stress red and processed meat and fat may be linked to an increased risk of colon cancer recurrence. Experts see promise for survivors in a diet rich in fruits, vegetables and whole grains, with low-fat dairy products — a pattern that may aid survival and avoid recurrence as well as keep at bay conditions such as heart disease and diabetes, she said.

Links or relationships have been seen between lifestyle factors and the risk of cancer recurrence, but more-direct evidence, from trials that actually test whether such things as exercising and losing weight reduce the risk of death after cancer diagnoses, is not yet available. Major survivorship studies are underway in such areas as colon cancer and exercise, breast cancer and weight loss, and ovarian cancer and lifestyle interventions.

A page from heart disease

The focus on survivor lifestyle takes a page from heart disease. Cardiac patients were once prescribed bed rest. President Dwight D. Eisenhower toppled that notion in the 1950s after he suffered a heart attack in office. With his doctors’ encouragement, he continued to work and returned to his favorite activities of walking, golfing and fishing. Today, getting heart patients moving as soon as possible is standard cardiac rehabilitation.

Researchers hope to develop similar care standards for cancer survivors, but more work is needed. “You can’t change policy without evidence-based research,” Nebeling said.

Missed benefits

As research continues, many survivors fail to incorporate lifestyle changes into their daily routines, often for financial reasons.

Schmitz conducts research trials of exercise interventions for breast cancer survivors. She was lead author of a study published in 2012 that followed 600 survivors for six years to assess needs and benefits of physical therapy and rehab exercise. At six years post treatment, more than 60 percent had at least one symptom that could have been helped by a physical intervention.

Schmitz has been angered to find that many in her studies had developed disabilities because the circumstances they returned to after treatment were ignored. The women had jobs — as child-care workers, nursing aides and cleaners, for example, that required much physical labor. Without adequate physical and occupational therapy, they returned to work and developed such severe upper-body difficulties that they became disabled.

Unlike many other countries, the United States lacks consistency in assessing cancer survivors’ needs and in funding rehabilitation, nutrition counseling and ongoing care. Ligibel said that survivors need an infrastructure that takes them from finishing treatment and being fatigued to a program of being more active and getting help with nutrition. It’s “hard for people to make these changes on their own,” she said.

Research into the possible links between lifestyle and cancer survival may help raise the profile of cancer rehabilitation. “Hopefully that will lead to better development of infrastructure and third-party payment to help people actually do these things,” she said.

Enormous strides have been made in keeping cancer patients alive, and lifestyle may help many rebuild survivors’ quality of life. “It is no longer enough to say, ‘Well, you’re alive,’ ” Schmitz said.

Ligibel said there is no doubt that many survivors are not living the way they want to. “I think our goal now is to give people the lives back they had before their diagnosis,” she said. “So we have to help them not only to live longer but also to live better than they are now.”