Update on RTOG Trial of Radiosurgery for Glioblastoma

Radiation Therapy Oncology Group (RTOG) trial 93-05 started slowly,but is now accruing on target, enrolling three patients per month,says Dr. Luis Souhami, chair of the study. To date, 40 patientsare enrolled in the study.

RTOG 93-05 is evaluating whether radiosurgery can increase localcontrol and survival of patients with glioblastoma multiforme.Toxicity and quality of life issues also are end points of thestudy.

The current treatment for patients with glioblastoma multiformeis surgery (if feasible) followed by external beam radiation therapyand carmustine (BCNU [BiCNU]).

All patients enrolled in RTOG 93-05 will undergo surgery (if feasible),conventional radiation therapy, and chemotherapy (BCNU). Conventionalradiation therapy will be given at 2 Gy in 30 fractions for atotal dose of 60 Gy in 6 weeks. BCNU (80 mg/m²) will be givenon days 1, 2, and 3 of radiation therapy, then every 2 monthsfor a total of six cycles.

Half of the patients will be randomized to also undergo radiosurgery,says Dr. Souhami. The radiosurgery dose is tumor dependent. Patientswith tumors 20 mm or less will receive 21 Gy; patients with tumors21 mm to 30 mm will be given 18 Gy; and patients with tumors 31mm to 40 mm will be treated with 15 Gy. Patients with tumors >40 mm after surgery are not eligible to participate in the study.Patients undergo radiosurgery before external-beam radiation treatmentsbegin.

Earlier studies have indicated that higher doses of radiationtherapy can increase median survival of these patients, says Dr.Souhami. "By adding radiosurgery we can give that higherdose of radiation to the brain while still sparing normal tissue,"he says.