All-out attack on deadly bone cancer.

All-out attack on deadly bone cancer

Total-body radiation and extra chemotherapy added to conventional treatment sounds like a drastic approach to a childhood cancer. Yet in the case of Ewing's sarcoma, the extra treatment may provide hope for patients at high risk of relapse and death, according to research presented last week at the American Cancer Society's 31st Science Writers' Seminar in Irvine, Calif.

Robert B. Marcus Jr. and his colleagues at the University of Florida in Gainesville have treated 20 high-risk patients with the experimental therapy; statistical projections indicate 60 percent will remain disease-free up to four years after the end of treatment. In contrast, 25 similar patients treated conventionally from 1977 to 1984 had only a 20 percent chance of disease-free survival after four years, Marcus reports.

Ewing's sarcoma, a particularly lethal cancer, usually strikes people between the ages of 10 and 25. Standard treatment involves radiation targeting only the primary tumor, followed by chemotherapy. But such treatment often fails to kill the microscopic seeds of cancer that have traveled to distant parts of the body. "Almost all of the patients are in complete remission as far as we can detect it after standard chemotherapy," Marcus says. "But we know from the cure rate that 80 or 90 percent will relapse."

To combat these odds, Marcus and his colleaues gave high-risk patients -- those with tumors larger than 10 centimeters and evidence of cancer spread -- five cycles of standard chemotherapy consisting of vincristine, cyclophosphamide and doxorubicin hydrochloride. Patients also got primary-tumor radiation. In addition, they received 800 centigrays of total-body radiation followed by a final chemotherapy dose.

The treatment is a harsh one. The radiation blast kills tumor cells, but it also destroys normal bone marrow and white blood cells, leaving patients vulnerable to life-threatening infection, Marcus says. The researchers take the bone marrow from each patient after the second chemotherapy cycle and transfuse it back into the patient's bloodstream after the final radiation treatment. Patients must remain in isolation for six weeks while the autologous transplant takes hold.

The researchers say they believe the transplanted marrow is cancer-free, pointing out that chemotherapy and freezing should kill any cancer cells. "We can't be 100 percent sure," Marcus notes, acknowledging that some patients have already relapsed. Other researchers, including Eli Glatstein at the National Cancer Institute, echo the uncertainty. Glatstein points to a trial, described in the March 1988 JOURNAL OF CLINICAL ONCOLOGY, in which he and his colleagues gave Ewing's sarcoma patient chemotherapy -- with drugs that differed from Marcus' regimen -- and total-body radiation followed by an autologous marrow transplant. The team's early success was marred by a high relapse rate three to five years after treatment, he says.

Marcus and his colleagues are tinkering with their regimen to make it safer and more effective. Long-range follow-up is needed to see whether these patients will survive the cancer and the treatment, Marcus says.