Cancer That Kills the Young May Have Met Its Match
"About 10 or 12 years ago, we realized that if we attached
a higher amount of radiation to the MIBG, we might be able to kill the
tumors," Yanik says. His team has now treated 11 children aged two to 14
years with a protocol of MIBG with high radiation followed two weeks later by a
high dose of chemotherapy. "It's a double knockout punch."
However, the knockout punch damages the bone marrow that
produces both red blood cells that transport oxygen and white blood cells that
fight infection. So one week after the chemotherapy, doctors transplant bone
marrow stem cells which had been previously harvested from the child.
"Think of it as using a chemical to take out the weeds but
in killing the weeds we kill the whole lawn. Then we need to put down new
seed," he says in explaining why bone marrow cells must be
Robert Seeger and Patrick Reynolds, doctors at the Children's
Hospital of Los Angeles, have developed a process to purge the patients' bone
marrow of any neuroblastoma cells that might be present. In this way,
physicians know that they are not reintroducing the disease.
Yanik says that the use of the MIBG radioactive compound
improves treatment outcome because shrinking of the tumors in all of the
children occurred before the chemotherapy dosage was administered.
"The current study is for those who would have less than a
10% cure rate; we have selected the most severe cases," he says. "The
tumor shrink rates showed promise; all [the patients] have achieved some
response and eight achieved remission within three months of therapy."
However he cautions that it's too early to know how much this
treatment will improve cure rates because none of the patients have been
followed long term. The researchers are still trying to discover the optimal
dosages of MIBG and of the chemotherapy.
Duke University researchers have collaborated with Yanik on the
protocol and are beginning treatment of their third patient. Each of the ones
they have seen has been two and one-half years old when accepted for the
therapy. Children diagnosed after the age of one usually have advanced disease
and their rate of survival is low.
"The two we have done are doing exceptionally well,"
says Timothy Driscoll, MD, of the Duke Pediatric Stem Cell Transplant Program.
"What's nice about this therapy is that the tumor cells have little bumps
that actually take up the chemical without harming the child's other cells.
"It's very exciting that we may be able to cure them and
spare them the toxicity. The children tolerate this treatment very
Driscoll and his colleagues will be trying something new with
their third patient. The young boy has so much damage to his bone marrow from
previous radiation and chemotherapy and so many neuroblastoma cells in it that
the purging process can't be used. "His bone marrow is just tired out,"
says Driscoll. Instead doctors will be using bone marrow from a sibling that is
a complete match.