Data on a study assessing the mortality rates among childhood cancer survivors was recently presented during the 2015 American Society of Clinical Oncology (ASCO) Annual Meeting held in Chicago, May 29 to June 2. The abstract was presented by Dr. Gregory T. Armstrong from St. Jude Children’s Research Hospital in Memphis, Tennessee and was entitled “Reduction in late mortality among 5-year survivors of childhood cancer: A report from the Childhood Cancer Survivor Study (CCSS)” (Abstract No. LBA2).
Childhood cancer treatment has changed significantly over the last four decades with increasing patient survival rates, follow-up care and reduction in the risk of life-threatening conditions. It has been previously estimated that up to 18% of five-year childhood cancer survivors die within 30 years post cancer diagnosis; and death in these cases is associated to three main causes: progression/recurrence of the primary cancer, external events (accidents or suicide) and other health-related causes, which are often linked to late effects of cancer therapy. Mortality associated with these causes is known to increase over time.
In this retrospective study, researchers examined data from the Childhood Cancer Survivor Study (an American-Canadian project that assessed long-term clinical outcomes in five-year survivors of childhood cancer diagnosed between 1970 and 1999) and the National Death Index (a database of death record information). The team assessed the mortality rates of 34,033 five-year childhood cancer survivors, all younger than 21 at the time of diagnosis. Patients were followed-up with for an average of 21 years after diagnosis. Mortality associated to health-related causes, including deaths due to late-effects of cancer therapy, were also evaluated.
Researchers found that 12% of patients died during the follow-up period, with 41% of these deaths due to other health-related causes besides cancer. The mortality rate within 15 years after diagnosis decreased by half in recent decades, from 12.4% in patients diagnosed in the early 1970s to only 6% in patients diagnosed in the early 1990s. Cancer survivors diagnosed in more recent years were also found to have a lower mortality rate linked to other health-related causes (2.1%) than patients diagnosed in the 1970s (3.5%).
The team suggests that this decrease in mortality is due to the lower number of deaths related to late effects of cancer therapy, most likely resulting from changes in care and gradual treatment optimization that reduced the intensity of therapy without compromising effectiveness, which in turn, decreased the risk for medical conditions like cardiac and lung disorders.
Mortality reduction was especially observed among survivors of disorders like Hodgkin lymphoma, a cancer that affects immune cells called lymphocytes, a type of white blood cell that defends the body from infections. Over time, the radiotherapy dose applied in patients with Hodgkin lymphoma has been reduced, as well as the cumulative dose exposure of anthracycline, a chemotherapy drug strongly linked to cardiac toxicity.
“Fifty years ago, only one in five children would survive cancer, and today over 80% are alive five years after diagnosis. Yet, these survivors still grow up with increased risk of dying from late effects, like heart disease and second cancers, (…) Now, we’ve not only helped more children survive their primary cancer, but we’ve also extended their overall lifespan by reducing the overall toxicity of treatment in more modern eras.” noted Dr. Armstrong in a news release. “While the modernization of cancer therapy has probably made the most significant difference, improvements in supportive care for survivors, and screening, detection, and treatment of late effects, like new cancers and heart and lung disease, have played an important role in extending their lifespan as well”.
Dr. Stephen Hunger concluded “For decades, we’ve strived to avoid the paradox in which children survive cancer, only to become sick or die years later because of the treatment they received. By carefully refining pediatric cancer treatment, we have improved long-term care and outcomes by leaps and bounds. Cure rates have increased with parallel decreases in death due to complications of cancer treatment. We hope that the positive trends we’re seeing today will continue as our therapeutic approaches continue to improve over time.”