Findings may account for relatively poor outcomes.
Second cancers in children and adolescents and young adults (AYA) are far deadlier than they are in older adults and may partially account for the relatively poor outcomes of cancer patients ages 15–39 overall, a new study by UC Davis researchers has found.

The study also found that survival after almost all types of cancer is much higher when the cancer occurs as a primary malignancy than if it is a second cancer, and these survival differences are most pronounced in patients under age 40. The article, entitled "Second Primary Malignant Neoplasms and Survival in Adolescent and Adult Cancer Survivors," was published in JAMA Oncology journal.

Researchers hope the findings help guide clinicians in providing age–specific recommendations on cancer prevention, screening, treatment and survivorship, especially among the AYA population for whom survival rates have not improved to the same extent as they have for children and older adults.

“Although the increased incidence of second cancers is well known among cancer survivors, less is known about outcomes of these cancers or the influence of age,” said Theresa Keegan, a cancer epidemiologist at the UC Davis Comprehensive Cancer Center and the study’s lead author. “Second cancers are a serious late effect of having a prior cancer and, for most cancers, have a substantial impact on survival.”

Keegan and colleagues at UC Davis, Oregon Health and Science University and the John Wayne Cancer Institute identified all patients diagnosed with only one or a first and second malignancy during 1992 through 2008 using Surveillance, Epidemiology and End Results (SEER) program data collected from 13 cancer registries. The researchers were careful not to capture recurrences of the same cancer when identifying secondary malignancies.

The authors collected data on the 14 most common cancer types that affect AYAs: female breast, thyroid, testicular, Hodgkin lymphoma, non–Hodgkin lymphoma, acute lymphoblastic leukemia, acute myeloid leukemia, soft tissue sarcoma, bone sarcoma, colorectal, central nervous system, cervical and ovarian cancer.

Overall, children and AYAs had an 80 percent chance of surviving five years after a diagnosis of a first cancer. But if the same cancer occurred as a secondary malignancy, 5–year survival dropped to 47 percent for children and 60 percent for the AYA population. The differences in survival were not nearly as marked in the older adult population, who had a 70 percent chance of surviving five years overall for a first cancer and 61 percent for a new, second malignancy.

When the researchers looked at 5–year survival by age and individual cancer types, they found striking differences depending on whether it was a first or secondary malignancy in all but two of the 14 cancer types, testes and melanoma.

For example, AYA patients diagnosed with acute myeloid leukemia as a first cancer had a 57 percent chance of surviving for five years, but that dropped to 29 percent if it was the second cancer. For AYA patients diagnosed with breast cancer, the 5–year survival was 81 percent for a first cancer but 63 percent if it was a second cancer.

Keegan said an explanation for worse outcomes may be that those with a secondary cancer have a worse response to treatment, limitations on the types or doses of treatments that they can receive as a result of their prior cancer treatment or impaired physiologic reserves that impact their ability to tolerate treatment.

Goldfarb added that psychosocial issues may play an important role, or combine with other factors such as an underlying biological condition that predisposes someone to cancer.