Whole-brain radiation therapy (WBRT) and stereotactic radiosurgery (SRS), when used together in the treatment of brain tumors, present a greater risk of significant decline in learning and memory function by four months, according to a randomized trial published in the November edition of Lancet Oncology.
Eric L. Chang, MD, associate professor of the division of radiation oncology at the University of Texas M. D. Anderson Cancer Center in Houston, and colleagues designed the randomized control trial to test their hypothesis that adding WBRT to SRS does not outweigh the possible neurocognitive risks associated with the treatment in the control of brain tumors.
In accordance with early stopping rules, the independent data monitoring committee supervising this trial terminated the study because there was a substantially higher probability (96 percent) that the patients randomly assigned to the SRS plus WBRT group would present a decline in memory and learning function at the four-month mark (mean posterior probability of decline 52 percent), as opposed to patients in the SRS only group at four months (mean posterior probability of decline 24 percent).
During the study, a total of 58 patients presenting one to three newly diagnosed brain metastases were recruited for trial. Thirty of them were classified in the SRS-treatment only group and 28 were placed in the SRS plus WBRT group. The patients were classified by recursive partitioning analysis class, number of brain metastases, and radioresistant histology. The researchers randomly assigned patients to either SRS plus WBRT or SRS alone from Jan. 2, 2001 to Sept. 14, 2007.
Both clinicians and patients were made aware of their treatment allocation at the point of assignation.
In the SRS plus WBRT group, there were eight deaths (29 percent) at the four-month mark, and 73 percent of the patients in this group were free from central nervous system recurrence at one year. Conversely, the SRS group experienced 27 percent CNS recurrence and half the amount of deaths at four months (four deaths).
Attributable to radiation treatment, Chang and his colleagues found one case of grade 3 toxicity (seizures, motor neuropathy, and depressed level of consciousness) in the SRS plus WBRT group. Likewise, one case of grade 3 toxicity (aphasia) was attributed to radiation treatment in the SRS only group.
Prior to the trial's termination, its determined endpoint was neurocognitive function, measured objectively as a significant deterioration (five-point drop compared with baseline) in the Hopkins Verbal Learning Test-Revised at four months.