JUDY WOODRUFF: Almost 80 percent of children who are diagnosed with cancer today in the U.S. survive, thanks in large part to advances in treatments like radiation and chemotherapy.

But a growing body of research indicates survivors are at greater risk for a host of health problems in later life, due to the very treatments that saved their lives.

The NewsHour's Cat Wise has our report.

CAT WISE: Laura Allaire has her hands full these days. A former nurse, she's now a stay-at-home mom raising two young daughters in Orinda, California, just outside San Francisco.

Allaire, who is 33, exercises often and does yoga. In many ways, she is the picture of health, but a decade ago, she was in a very different place.

LAURA ALLAIRE, Pediatric Cancer Survivor: I was diagnosed when I was 12 years old with Hodgkin's lymphoma.

CAT WISE: Allaire was in seventh grade when she learned she had cancer. She kept a journal detailing a grueling year of hospital visits and treatments.

LAURA ALLAIRE: "After Dr. Morgan has checked me and says I'm healthy enough, she says I can get my chemotherapy. For chemo, my medicines are ordered and then I go see Melody. Melody gives me my medicine through a port."

CAT WISE: The chemotherapy and radiation Allaire received are well-known weapons in the battle against cancer. Powerful chemicals in chemotherapy drugs attack cells that are rapidly dividing. And high-energy beams used in radiation kill cancer cells by damaging their DNA.

LAURA ALLAIRE: I had a mass in my chest, and so the radiation was directed there. And my doctors actually gave me a small tattoo after I was done with the radiation, so that I would always know exactly where the radiation was directed towards.

CAT WISE: But, ironically, the same treatments that saved Allaire's and so many other cancer patients' lives also come with a downside. In the process of killing the cancer cells, they can damage surrounding healthy cells, which can lead to other health problems known as late effects.

That's particularly dangerous for those who beat cancer when they are young and have years to develop late effects. A recent study found that adult survivors of childhood cancer are five times more likely than their siblings to develop new cancers, heart problems and other serious health conditions after the age of 35.

DR. ROBERT GOLDSBY, Survivors of Childhood Cancer Program, University of California, San Francisco: The good news is, more people are surviving cancer. The bad news is those that survive, more than half have a long-term issue.

CAT WISE: Dr. Robert Goldsby is a pediatric oncologist at the University of California, San Francisco, Benioff Children's Hospital. And he directs the Survivors of Childhood Cancer program, also known as the Survivors Clinic.

It's one of a number of similar programs around the country that are caring for the more than 300,000 survivors of pediatric cancer and studying their long-term health.

WOMAN: How are you feeling today? Can I listen?

CAT WISE: In addition to getting frequent checkups, survivors and their families are educated about health risks they face, based on the specific treatments they received, and where they received them.

DR. ROBERT GOLDSBY: The organs in our bodies can be beaten up by the chemotherapy, the radiation, the surgeries. So, we have to monitor heart function, lung function, liver, kidneys, all the organs. Some survivors deal with infertility, post-traumatic stress syndrome.

CAT WISE: Laura Allaire knows all too well the possible side effects of the radiation and chemo treatment she received as a child. On a recent day, she was at the Survivors Clinic for a regular checkup with Dr. Goldsby. Last year, Allaire had her thyroid removed after an ultrasound revealed a suspicious growth. And she's been on medication for a heart problem, conditions Dr. Goldsby says are likely caused by her cancer treatments as a youngster.

But about 5 percent of all pediatric cancer survivors face a far more serious repercussion: secondary cancer. That risk increases with age and with certain therapies.

Eleven-year-old Samantha Schwarz is battling cancer for the second time in her life. The bone cancer discovered in her temple last year was most likely caused by radiation she received in the same area as an infant to treat a tumor behind her left eye.

SAMANTHA SCHWARZ: It's been a little tough coming to the hospital every two weeks. It's been tough not seeing my brother, and my dog, and my dad.

DR. ROBERT GOLDSBY: And the radiation probably came this way and this way and this way.

CAT WISE: Dr. Goldsby helped to diagnose Samantha's second cancer while she was being seen at the Survivors Clinic at UCSF Benioff Children's Hospital in San Francisco.

DR. ROBERT GOLDSBY: And this round thing there, that's your second cancer. And it's related to your treatment.

The fact that they have to go through therapy again may increase their risk for other long-term-related issues.

Marilyn Schwarz is Samantha's mom.

MARILYN SCHWARZ: The doctors did tell us about some of the after-effects of chemotherapy and radiation, but, for us, there was no choice. We just knew that our child needed help right away. So when the doctors told us the second cancer was here in the head, in the same spot, I think, for both my husband and I, our hearts just dropped.

CAT WISE: Besides just living longer than adults treated for cancer, there's another reason pediatric patients are more at risk for recurrences, according to Dr. Jean Nakamura, a radiation oncologist at the university.

DR. JEAN NAKAMURA, Radiation Oncology, University of California, San Francisco, Benioff Children's Hospital: Young children have developing tissues. They undergo rapid proliferation of — multiple organs are growing. There's a lot of cell activity, and so that probably is a basic reason that contributes to second cancer risk uniquely in young children, as compared to everybody else.

CAT WISE: Dr. Nakamura is leading a team of scientists who are studying the genetic makeup of second cancer tumors to understand why they form in some patients after treatment.

DR. JEAN NAKAMURA: If one could identify genes or molecular pathways that are specifically altered in second cancers, we might actually be able to screen for second cancers, and not have to wait until something develops and is visible.

CAT WISE: But, as research continues to unfold into secondary cancers and other late effects caused by chemo and radiation, doctors treating critically ill patients today must still rely on those same treatments.

Dr. Mignon Loh is chair of pediatric molecular oncology at Benioff Children's Hospital.

DR. MIGNON LOH, Pediatric Molecular Oncology, University of California, San Francisco: I would say that most families are really focused on getting their child to feel better, and I think that's where their focus should lie.

I think, as physicians, we have the responsibility to inform them about potential late effects, not to completely overwhelm them. But I would say our priority currently remains curing the first cancer. And I don't think anybody wants to compromise on the ability to cure the first cancer.

CAT WISE: For her part, survivor Laura Allaire says she doesn't like to dwell on what might lie ahead.

LAURA ALLAIRE: I don't think about it on a daily basis, because that's not how I want to live my life. I have been through a lot, and I understand that this isn't something that most people go through. But I'm in a unique situation, and I need to be proactive and make sure I take care of myself.

CAT WISE: And she goes forward more knowledgeable about what she went through as a child, and hopeful for a healthy future.

JUDY WOODRUFF: On our Web page, you can see what all patients of UCSF Survivors Clinics receive, a health passport, which gives detailed information about their past treatments and follow-up care they need in the future.