August 15, 2002 (American Society of Clinical Oncology) -- An international study of more than 32,000 Hodgkin's disease patients has shown that long-term survivors of the disease have double the normal risk of developing a subsequent cancer later in life. Researchers led by the National Cancer Institute measured the risk of these "second cancers" among Hodgkin's disease survivors using data from cancer registries in the U.S., Canada, and four Nordic countries. The research tracked cancer incidence and had among the longest follow-up periods of any study to date. Of the study population, 1,111 patients were followed for 25 years or longer.
The study found that the relative risk for developing a second cancer--compared to that of the general population--was significantly elevated in every age group of Hodgkin's disease survivors studied. Overall, survivors were twice as likely to develop a solid tumor, compared to the general population. This cancer risk remained significantly elevated for 25 years or more.
The researchers also found that the relative risk of solid tumors appeared to begin to decline 25 years after diagnosis of Hodgkin's disease. Previous studies had indicated that the risk of second cancers persisted for at least 20 years. However, the researchers cautioned that further study is needed to more precisely estimate risk after 25 years, given the comparatively small number of patients followed for this length of time.
"The long-term decline in relative risk for many solid tumors 25 years or more after Hodgkin's disease diagnosis was a notable finding," said Graηa M. Dores, M.D., of the National Cancer Institute, lead author of the study. "However, risks remained elevated compared to the general population, and further study is needed to confirm these results. Patients and their physicians need to remain aware of the persistent long-term risk of second cancers after treatment for Hodgkin's disease."
This study and earlier research has suggested a link between certain Hodgkin's disease treatments and increased risk of second cancers. However, Dr. Dores stressed that the findings should in no way discourage patients from undergoing therapy for Hodgkin's disease: "We have very effective therapies for this disease, which is now associated with an overall five-year relative survival rate of 85 percent. The benefits of treatment greatly outweigh the risk of developing a second cancer."
Unlike most other solid tumors, the increased relative risk for female breast cancer did not appear to decline at 25 years or beyond. Chest radiotherapy, including that used for treatment of Hodgkin's disease, is a well-established risk factor for breast cancer development. Among women with Hodgkin's disease, breast cancer accounted for the largest number of excess cancers, beyond what would be expected in the general population.
Dr. Dores also noted that treatment for Hodgkin's disease changed significantly over the period of the study, and that second cancer risk among long-term survivors often reflects earlier treatment protocols.
"This study provides a springboard for future research on the long-term effects of Hodgkin's disease and its associated treatments," Dr. Dores explained. "It provides us with a firm basis for future studies that account for specific treatments and tumor types."
