Ewing Sarcoma with New Approach 

During the past two decades there has been little improvement in the long-term survival rate of 75 percent for children and young adults with Ewing sarcoma whose cancer did not spread.

Survival for those whose disease returns after treatment is completed remains a dismal 20 percent or less.

“For us at St. Jude Children’s Research Hospital, this is just not good enough,” said Elizabeth Stewart, MD, a research associate in the hospital’s Department of Oncology. “This was an opportunity for us to spend some extra time studying it and, because these tumors are rare, it makes for a more challenging study.

“But with advanced technology in combination with some of the efforts of the Pediatric Cancer Genome Project, we’re discovering new ways to learn about the biology of these tumors and how else to treat them.”

Ewing sarcoma (EWS) is a cancerous tumor that grows in the bones or soft tissue and can occur in the legs, the pelvis, the ribs, the arms, the spine or just about any bone in the body. It spreads most often to the lungs, but can spread to other bones or into the bone marrow.

EWS is considered rare, yet is the second-most common type of bone cancer seen in children. About 200 children or young adults are found to have EWS each year in the United States and about half of those involve patients ages 10 to 20.

St. Jude sees 10 to 15 newly diagnosed EWS patients each year, while also doing considerable consultation and treating other patients whose disease has returned.

That posed a challenge for a team of doctors that includes both PhD and MD training.

“At St. Jude, these types of collaborative research efforts between PhDs and MDs are the norm,” said Michael Dyer, PhD, director of the hospital’s Division of Developmental Biology. “In fact, St. Jude was founded on the principle that to improve outcomes for childhood cancer, we must work across disciplines and bring the best science to the clinic.”

The current treatment for EWS involves a combination of surgery, chemotherapy and radiation, but soon a pair of clinical trials will begin, one using a two-drug combination for patients age 1 and older. A second trial – in collaboration with researchers at the Dana-Farber/Harvard Cancer Center in Boston – will use a three-drug combination for patients 16 and older.

The trials involve two chemotherapy drugs now being used to treat EWS with experimental drugs called poly-ADP ribose polymerase (PARP) inhibitors that interfere with DNA repair. PARP inhibitors already are in clinical trials in the treatment of some breast and ovarian cancers and other solid tumors.

The two-drug trial involves the use of the chemotherapy drug irinotecan with the PARP inhibitor talazoparib. Three-drug trial includes the chemotherapy drug temozolomide and irinotecan and the PARP inhibitor olaparib.

The trials are the result of a study that built on earlier research showing EWS cells in the laboratory were sensitive to olaparib. The new study noted that EWS cells have a defect in DNA damage repair and that this defect can be exploited to help patients by combining DNA-damaging chemotherapy with a PARP inhibitor.

Dyer said more than 30 experts have contributed to the research project.

“It really took a village to do this type of study,” added Stewart. “Fundamentally, the training for PhDs and MDs is different, but we capitalized on the strengths of both to find the best treatment for these children at St. Jude.”

Stewart, Dyer and Anang Shelat, PhD, an assistant member of the St. Jude Department of Chemical Biology and Therapeutics, are the corresponding authors of the study.

The clinical trials, which are expected to last two to three years, will begin as soon as FDA approval is given.