Low-dose radiation for Hodgkin's lymphoma leaves kids at high risk for second cancers

NEW YORK (Reuters Health) - Low-dose radiation for Hodgkin's lymphoma leaves children at a significant risk for second malignancies, according to researchers at Stanford University Medical Center in California.

"Because it is now well established that radiation exposure is associated with the development of second cancers, particularly solid tumors, later in life, we wanted to find out if adult survivors treated with a lower dose radiation based protocol as children would suffer second cancers," lead author Dr. Maureen M. O'Brien told Reuters Health by email. Dr. O'Brien is now at Cincinnati Children's Hospital Medical Center in Ohio.

In a February 1 online paper in the Journal of Clinical Oncology, she and her colleagues report on 110 pediatric Hodgkin's lymphoma survivors who received chemotherapy and low-dose radiation between 1970 and 1990. The children were treated with two combined modality treatment protocols that included 6 cycles of chemotherapy in addition to 15 to 25.5 Gy involved-field radiation plus 10 Gy boosts to bulky sites.

During follow-up over a median of 20.6 years, 18 patients developed at least one second cancer, including 4 cases of leukemia, 17 solid tumors, 5 thyroid carcinomas, 6 breast carcinomas, and 4 sarcomas.

The estimated cumulative incidence of an initial second malignancy was 17% at 20 years and 29.4% at 30 years after diagnosis. "The majority of the risk is due to solid tumors with a cumulative incidence of 14.3% at 20 years...and 27.2% at 30 years," the authors write.

Among patients who developed solid tumors, the mean 5-year disease-free survival was 76%, and the mean 5-year overall survival was 85% (with a median follow-up of 5 years since the diagnosis of the initial second cancer).

All of the patients with secondary leukemias died.

The standard incidence ratio for any second cancer was 22.9, and the absolute excess risk was 93.7 cases for every 10,000 person-years.

"These results support the need for continued basic science research to better understand the genetic factors that predispose some survivors to develop second cancers while others do not, despite exposure to similar treatment," Dr. O'Brien noted.

She added that the results are a "reminder of the importance of the need for ongoing care and education of cancer survivors, with close surveillance and screening for second cancers as well as other long term effects of treatment."

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