MONDAY, Nov. 7, 2016 (HealthDay News) -- Despite three decades of advancements in treating children with cancer, patients who survive into adulthood don't report better physical or mental health than their counterparts who were treated years ago, researchers report.

Adults treated as children in the 1990s were more likely to report poor general health and anxiety than adults treated as children in the 1970s, the researchers said.

That's not what the researchers had expected to find. After all, patients are living longer today than in past generations. More than 80 percent of children diagnosed with cancer are alive at least five years after their diagnosis, the U.S. National Cancer Institute says.

And there have been significant efforts to minimize the toxic side effects of cancer treatments. Proton therapy limits radiation damage to healthy tissue, while limb-sparing surgery has largely replaced amputation, noted Kirsten Ness, a physical therapist and one of the study authors.

"I kept looking at the data, thinking, 'This can't be right,' " said Ness, a faculty member in the Department of Epidemiology and Cancer Control at St. Jude Children's Research Hospital in Memphis, Tenn.

"We were sort of expecting that they wouldn't have as many problems with their perceived health as survivors who were treated in earlier generations," she said.

Pam Gabris is coordinator for Beyond the Cure, a program of the National Children's Cancer Society (NCCS) in St. Louis. Beyond the Cure prepares survivors and their families for life after cancer.

While the study results are "disappointing," survivors' awareness of potential complications, or "late effects," of cancer treatment is improving, according to Gabris, a registered nurse.

"Now we have to provide the tools they need to manage their health," she said.

NCCS, for example, offers an online tool that allows survivors to plug in information about their cancer and view specific information on potential late effects they may experience, symptoms, prevention tips and recommendations for follow-up care.

Two-thirds of all survivors experience one or more late effects from their disease, their treatment or both, NCCS says.

There are an estimated 15.5 million cancer survivors in the United States, the National Cancer Institute reports.

For the new review, led by St. Jude, researchers from Toronto and across the United States reviewed information from the Childhood Cancer Survivor Study. This is a long-term, multi-hospital study that captures data from survivors' medical records.

The study originally included patients diagnosed between 1970 and 1986 and recently was expanded to include patients who received a diagnosis between 1987 and 1999.

The research involved more than 14,500 adults, now ages 18 to 48, who survived five or more years after diagnosis. All were treated as children between 1970 and 1999.

The analysis relied on patients' own reports of their overall physical and mental health, ability to function, activity limitations and cancer-related anxiety or pain.

The proportion of patients reporting severe, disabling or life-threatening chronic conditions declined from more than 33 percent among those treated from 1970 to 1979 to 21 percent among those who were treated from 1990 to 1999.

Yet reports of adverse health outcomes did not decline by generation.

Leukemia and osteosarcoma (cancer of the bone) survivors, in particular, reported sharply higher rates of adverse outcomes.

More than a third (37 percent) of osteosarcoma patients treated in the '90s reported cancer-related pain, for example. For those osteosarcoma patients treated in the '70s, about a quarter (24 percent) said they had cancer-related pain.

The lingering pain may be related to limb-sparing surgery, leading to multiple limb-lengthening procedures as kids grow, Ness said. Or, it could be the result of deformities that cause people to walk with a limp, she said.

Some survivors reported significant difficulty getting around or performing day-to-day activities.

Anxiety was also a problem. Ness suspects that the younger generation, unlike children of the '70s and '80s, are given permission to worry.

It's possible today's survivors "truly have worse outcomes," since more people who would have died in previous generations are beating higher-risk disease, Ness reasoned. It may also be that they have expectations of a higher quality of life.

Ness said the findings can help inform future clinical trials, with the goal of devising treatments that are less toxic. The study also points to the need for better follow-up care, including treatment for smoking, drinking, lack of exercise and poor diet, which were associated with adverse health outcomes in the study.

The study was funded in part through a grant from the U.S. National Cancer Institute. The findings were published Nov. 7 in the Annals of Internal Medicine.

More information

The U.S. National Cancer Institute has more on childhood cancers.