In the 1950s -- a heady time for scientific and medical advances -- the color television was introduced to the American public and Jonas Salk discovered the polio vaccine. But a diagnosis of acute leukemia, the most common form of childhood cancer, would have been a sure death sentence.
Only 40 years later, scientists were not only busy cloning sheep and sending space probes to Mars, but they could also boast an almost 4,000 percent increase in survival rate for children with leukemia -- a figure that continues to rise.
More than 3,000 children are diagnosed with acute lymphoblastic leukemia every year, and while the cancer is more common in children younger than 5 years old, more than 12 percent of those diagnosed are older than 15.
In general, the prognosis for all of these young patients is good, with more than 85 percent still alive after five years. But for some reason, adolescents and teens don't seem to fare as well as their younger counterparts. How much worse they fared was not really known until today.
This revelation came with the results from the largest clinical trial to study how well chemotherapy worked against leukemia in adolescent and young adult patients, presented at the American Society of Clinical Oncology annual meeting in Chicago.
Researchers found that the five-year survival rate for adolescents and young adults was 80 percent, compared with younger children who enjoyed an 88.4 percent rate of survival. Moreover, those older than 15 were also about twice as likely to relapse or die from the treatment itself.
Leukemia is a cancer of the blood cells. These rapidly reproducing cells travel quickly through the blood stream wreaking havoc and invading every nook and cranny of the human body, unless they are stopped. Normal treatment, using chemotherapy, takes three years to complete, isn't without its own downsides, and it doesn't work as well in some as it does in others.
Dr. Eric Larsen, medical director of the Maine Children's Cancer Program and lead study author, said in an ASCO news release that one reason older teens and young adults tend not to do as well is that not all types of leukemia are created equal -- in other words, older patients tend to have more deadly, less curable forms of the disease. He also noted that not only do these older patients tend to have a disease that is more resistant to chemotherapy, but they also experience more toxic side effects from the treatment they receive.
Other doctors said this double whammy deserves more consideration when treating teens and young adults with ALL.
"It's really a double-edged sword," says Dr. Peter Adamson, chairman of the Children's Oncology Group, the world's largest organization devoted to childhood and adolescent cancer research. "Their outcome isn't good, and their ability to tolerate treatment isn't good either."
Exactly why these differences exist in the first place is less clear. Adamson said the underlying disease may have different biological characteristics. Additionally, an important component of treatment involves taking a pill every day for more than two years.
"Compliance is harder for adolescents and young adults" Adamson says, explaining that this may also contribute to worse outcomes in this population.
And then there is the state of the research. More than 90 percent of children who get leukemia in the United States participate in studies like this one -- a "major factor" that has led to better cure rates, says Adamson. But, he notes, "One of the gaps has been in the older adolescent and young adults, where participation is not as high."
Whatever the reasons, Adamson says the results reported at today's meeting will help guide the Children's Oncology Group in designing additional clinical trials to both enhance leukemia control and reduce the toxicity of treatment in this sub-group of patients.