Adolescents and adults under 40 who have been successfully treated for cancer are at heightened risk of developing a second unrelated cancer, on average 15 years later, according to a study published on Tuesday, Oct. 6.
The study, published in the journal Cancer, is the first to broadly quantify this risk among patients who had been treated for a primary malignancy between the ages of 15 to 39.
“This is a patient demographic that has been largely overlooked,” said senior author Robert Goldsby, MD, a professor in the Department of Pediatrics at UCSF Benioff Children’s Hospital San Francisco. “While cancer survivors under 15 are at highest risk for developing a second cancer, cancer in children is actually very rare. There are eight to 10 times as many primary cancers in adolescents and younger adults than primary cancers in children.”
The researchers combed through the National Cancer Institute’s registry to obtain data on cancer prevalence. In determining that a cancer was a second malignancy, rather than recurrence or metastasis, they excluded cases that were of the same cancer type, as well as those that had occurred within five years of the first diagnosis.
Goldsby and colleagues narrowed their investigation to the most common primary cancers in the 15 to 39 age-group: leukemia, lymphoma, testicular, ovarian, thyroid, breast, soft tissue and bone cancers. They omitted brain tumors due to the variations in outcomes.
The researchers found that the cumulative incidence of a second cancer over a 30-year period for this age-group was 13.9 percent. When they compared their cancer risk to the age and gender-matched general population, it was found to be 58 per cent higher. In contrast, those survivors who had been diagnosed over 40 were 10 percent more likely to get cancer than the age and gender-matched general population.
“Cancer patients used to be told that after they had reached five years of remission, they no longer had special health care needs, but our study demonstrates that adolescent and younger adult survivors require lifelong follow-up with regular medical screening,” said Goldsby.
“In older adults, cancer is frequently the result of aging and the cumulative effects of long-term exposures or habits, such as smoking or unhealthy diet. But younger patients may harbor genetic changes that influence the risk of cancer. They may need counselling if their lifestyle choices increase their existing risk.”
The researchers found that the adolescent and younger adult survivors were diagnosed with a second malignancy on average 15 years later. The most common second cancers for this younger group were breast, gastrointestinal and genital cancers, and melanoma. Survivors whose treatment included radiation therapy had a higher risk of a second cancer: 17.6 percent versus 12.4 percent at 30 years post first diagnosis.
Of the 7,384 adolescent and younger adults that developed second cancers, 1,195 developed a third cancer.
“These results could have treatment ramifications for adolescents and younger adults diagnosed with cancer,” said co-author Rebecca Olin, MD, a professor in the UCSF Department of Medicine. “For example, for patients with Hodgkin lymphoma, efforts to reduce the use of radiation may be especially important. For female survivors, breast cancer is the most common second cancer and therefore mammograms are paramount.
“Ultimately more research is needed to understand how best to translate these findings into clinical practice, but this study clearly identifies and describes a previously under-appreciated problem,” she said.
Approximately 70,000 people ages 15 to 39 are diagnosed with cancer each year, according to the National Cancer Institute. Cancer is the leading cause of disease-related death in this population.
This study was supported by a grant from Swim Across America, which is dedicated to raising money and awareness for cancer research, prevention and treatment through swimming-related events.
Other authors are Jean Lee, MD, and Steven DuBois, MD, of UCSF Benioff Children’s Hospital San Francisco; Peter Coccia, MD, of the University of Nebraska Medical Center in Omaha; and Archie Bleyer, MD, of the Oregon Health and Science University in Portland.
UCSF is a leading university dedicated to transforming health worldwide through advanced biomedical research, graduate-level education in the life sciences and health professions, and excellence in patient care. Founded in 1864 as a medical college, UCSF now includes top-ranked graduate schools of dentistry, medicine, nursing and pharmacy; a graduate division with world-renowned programs in the biological sciences, a preeminent biomedical research enterprise and top-tier hospitals, UCSF Medical Center and UCSF Benioff Children’s Hospitals.