Childhood cancer survivors may face a higher than average risk of hospitalizations and cognitive challenges later in life, two recent studies in JAMA Oncology suggest.

One study in Denmark tracked more than 33,000 people who'd had cancer as adolescents or young adults, following more than half of them for at least 14 years. During the study, these survivors were 38 percent more likely to be hospitalized than 228,000 similar people who didn't have a history of cancer.

A much smaller study in the U.S. followed 80 survivors of the most common type of childhood bone cancer for about 25 years and found they had worse reading skills, attention spans, memory and other cognitive abilities than 39 similar people without any prior malignancies.

Taken together, the findings suggest that as advances in cancer therapy increase survival odds and transform the disease from a death sentence to a chronic illness for many people, doctors need to focus more on the long-term side effects of treatment, Dr. Karen Effinger and Dr. Michael Link of the Stanford University School of Medicine in California argue in an editorial accompanying the studies.

"I hope these studies will inform patients and physicians about some of the potential problems survivors face and will help to encourage better surveillance," Effinger said by email. "In adolescent and young adult patients, we need to continue to research the spectrum of late effects."

For the Danish study, researchers followed five-year survivors of adolescent or young adult cancer who were diagnosed from 1943 through 2004 to see how often they were hospitalized compared to similar people who never had tumors.

Cancer survivors had double the odds of hospitalizations for diseases of the blood and blood-forming organs. They were also 69 percent more likely to be hospitalized for infectious and parasitic diseases and had 63 percent higher odds of hospitalizations for malignant growths.

Risks varied based on the original tumor type. Survivors of leukemia were more than twice as likely to be hospitalized as people without a cancer history, while the odds were 93 percent greater after brain cancer and 87 percent higher after Hodgkin lymphoma.

"This information is highly valuable in the future planning of initiatives aiming to minimize or prevent adverse late effects in survivors of adolescent and young adult cancer," said Katherine Rugbjerg of the Danish Cancer Society Research Center, who co-authored the study with colleague Dr. Jorgen Olsen.

"Based on our study, doctors following this particular group of cancer survivors now know more accurately what to be aware of or look for in order to offer treatment for late effects caused by the cancer treatment as early as possible," Rugbjerg added by email.

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The U.S. study examined cognitive skills in survivors of childhood osteosarcoma and found they lagged their peers without a history of cancer in a variety of cognitive skills.

Researchers reviewed medical records from the original cancer treatment and found the cognitive impairment linked to current chronic health conditions rather than to previous use of high-dose methotrexate to attack tumors.

These results are surprising because methotrexate has been linked to long-term cognitive problems in other cancer diagnoses, said senior study author Kevin Krull of St. Jude Children's Research Hospital in Memphis.

"We found that they indeed were having cognitive problems but the problems were related to cardiopulmonary health and not the methotrexate exposure," Krull said by email. "It tells us that if we can maintain good cardiac health in these survivors as they age into middle adulthood, they may be less at risk for cognitive problems."