Purpose: To study patterns of recurrence in patients with focal primary glioblastoma treated on Northern California Oncology Group protocol 6G-82-2 including surgery, focal external beam radiotherapy (59.4-60 Gy) with oral hydroxyurea followed by temporary brain implant with high-activity iodine-125 sources (50 Gy), and six cycles of chemotherapy with procarbazine, lomustine, and vincristine.
Methods and materials: Serial brain imaging scans were available for review in 25 of 34 patients with glioblastoma who underwent brain implant boost. Of 381 scans performed between the date of diagnosis and the date of death or last follow-up, 362 (95%) were re-reviewed. Disease progression was scored as local (within 2 cm of the implant site), separate within the brain parenchyma (> or = 2 cm from the implant site), subependymal, or systemic. Both initial and subsequent failures were scored.
Results: Three patients are 5-year survivors, without evidence of disease, at 267, 292, and 308 weeks. Of the 22 initial sites of failure, 17 (77%) were local, three (14%) were separate brain lesions (one of which was due in retrospect to multicentric disease at diagnosis), one (5%) subependymal, and one (5%) systemic. Five patients with local failure later had other sites of failure, including a separate brain lesion in 1, subependymal spread in 3, and both in 1. One patient with separate brain failure later had local progression and then subependymal spread.
Conclusion: Although there was a significant risk of separate brain lesions or subependymal spread over time, local tumor progression was the predominant pattern of failure.