NIMG-40. TUMOR PROGRESSION BETWEEN SURGERY AND INITIATION OF ADJUVANT CONCURRENT CHEMORADIATION IN NEWLY DIAGNOSED GLIOBLASTOMA PATIENTS

Abstract

Glioblastoma remains a challenge due to its propensity for recurrence. Timely initiation of adjuvant chemoradiation after surgery has been encouraged due to fear of interval tumor progression. To characterize the incidence and clinical significance of tumor growth/progression between resection and chemoradiation, MRIs of 106 patients with newly diagnosed glioblastoma, enrolled on successive upfront trials at UCSF with similar eligibility, were analyzed by neuroradiology at three different time points: prior to surgical resection, after surgery, and prior to initiation of chemoradiation. The pre-chemoradiation images were compared to the postsurgical diffusion weighted imaging (DWI) to differentiate postsurgical infarct from increased enhancement attributable to tumor progression. New or increased contrast enhancement (CE) was seen on pre-chemoradiation scan in 66 patients. In 18 patients, new CE was seen only in the diffusion restricted areas seen on post-operative scan, while in 48 patients, the CE was indicative of tumor growth/progression. Median survival was 15.5 months for patients who had interval tumor progression and 21.7 months for patients who did not. A greater proportion of patients who suffered interval tumor growth had received less than gross total resection at time of surgery (75% vs. 34%, respectively). Interestingly, there was no significant difference in the time interval between surgery and initiation of chemoradiation between patients who had and did not have early interval tumor growth after surgery (29 and 32 days respectively). Increased CE indicative of tumor growth between surgery and chemoradiation is seen in nearly half of patients with newly diagnosed glioblastoma, and it appears associated with worse survival outcomes. Achieving gross total resection is associated with a lower likelihood early interval tumor growth prior to chemoradiation, however it remains unclear whether earlier initiation of chemoradiation would be beneficial. Relationship to other variables such as age, KPS, extent of resection etc. also will be discussed.