Cancer

08 September 2006

Stem cells fight child cancer

A highly targeted treatment that relies on the patient's own stem cells improves outcomes for children with brain tumours called medulloblastomas, US researchers report.

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A highly targeted treatment that relies on the patient's own stem cells improves outcomes for children with brain tumours called medulloblastomas, US researchers report.

Children with high-risk medulloblastoma have a 30% to 40% chance of surviving to five years, and chemotherapy usually lasts for about 12 months.

"Not only can we now cure about 70% of children with high-risk medulloblastoma, we can also cure more than 80% of those with standard-risk disease with a shorter, and therefore more convenient, chemotherapy approach," lead researcher Dr Amar Gajjar, from St Jude's Children's Research Hospital in Memphis, said in a prepared statement.

In this new treatment regimen, radiation therapy is tailored to the severity of the disease and is then followed by a shorter course of chemotherapy than used by doctors in the past. The new regimen resulted in substantially improved survival, say researchers reporting in the September 7 online edition of The Lancet Oncology.

Implanting stem cells
The shorter course of chemotherapy is made possible because stem cells taken from the child before chemotherapy are implanted after each round of chemotherapy, essentially allowing the child's body to recover from the damage caused by chemotherapy before the next round begins.

In their study, Gajjar's team treated 134 children with medulloblastoma. The researchers adjusted doses of radiation therapy depending on how severe the disease was. Children were classified as "standard-risk" cases if any tumours remaining after surgery were small and there was no evidence that cancer had spread to the rest of the body. Children were classified as high risk if they had larger tumours, or any evidence of metastasis.

During treatment, children in the high-risk group were given higher doses of radiation than the children in the standard-risk group. Both groups were given a shortened course of chemotherapy and a re-infusion of bone marrow stem cells after each cycle of chemotherapy, the researchers said.

By using their risk-adapted approach to radiotherapy, Gajjar's group was able to increase the survival rate of affected children to about 70%.

Alleviating neurotoxicity
"By reducing the amount of [chemotherapy drug] cisplatin from eight doses to four doses, and the amount of vincristine from 32 doses to just eight doses, we could alleviate a lot of the neurotoxicity associated with the higher dose of vincristine without reducing survival," Gajjar said. He believes the findings could mark a real advance in neuro-oncology.

"Our research focused on understanding the biology of medulloblastoma," Gajjar explained. "We now need to develop a biological system of staging that works in conjunction with the current clinical staging system, to further refine treatment for this disease."

Until then, "investigators should consider adopting a similar therapeutic strategy to ours for their high-risk patients," Gajjar said. "This approach should be feasible in most pediatric oncology units at academic medical centers, but meticulous staging and careful attention to detail during radiotherapy planning and treatment are essential to obtaining similar outcomes," he added.

However, another expert said the findings won't change her current practice.

Statistics not that different
"What the researchers have shown is that, with comparable doses we have used in the past, you can treat children with medulloblastoma with intense chemotherapy and stem cell rescue and get results pretty close to what has been reported in the past with other intensive treatments," said Dr Anna J. Janss, co-director of the Neuro-Oncology Program at the Aflac Cancer Center of Children's Healthcare of Atlanta.

Moreover, the groups' survival statistics are not very different from what has been published for the two risk groups in the past, Janss said.

"This study doesn't make me say: 'Oh, I want to treat all my patients this way,'" Janss said. "It makes me say this is an approach that is as good as what has been done before, but it doesn't make me want to harvest stem cells from every child I take care of," she said.

For standard medulloblastoma, Janss said she wouldn't use short-course chemotherapy. "The survival statistics aren't sufficiently impressive for the standard-risk group to justify the cost of this intensive treatment," she said. "The last results published showed five-year survival at 79 percent, which is statistically no different than this study."

"When you look at the high-risk group, the survival statistics are not a whole lot different from what's been published," Janss said. "At five years, survival is as high as 67%. I'm not sure that's a real difference." Janss also noted the researchers didn't comment on the long-term effects of their treatment.

"The disease is horrible, and the treatment has significant consequences on the child's brain function, learning ability, memory and hormone function," she noted. -(HealthDayNews, September 2006)

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