Interim Tumor Progression and Volumetric Changes of Surgical Cavities during the Surgery-to-Radiotherapy Interval in Anaplastic Gliomas: Implications for Additional Pre-radiotherapy Magnetic Resonance Imaging

PURPOSE

This study was designed to investigate the incidence of interim disease progression (IPD) and volumetric changes of the surgical cavity (SC) during the surgery-to-radiotherapy interval (SRI), and eventually assess the value of magnetic resonance imaging (MRI) at the time of radiotherapy (RT) planning in newly diagnosed anaplastic gliomas.

MATERIALS AND METHODS

Among 195 anaplastic glioma patients who underwent RT, 121 were evaluable with two separate MRIs during SRI. The presence of IPD was determined using the updated Response Assessment in Neuro-Oncology size criteria. In 84 patients who underwent surgical resection, each SC was contoured by a radiation oncologist and the volumetric changes of the SCs were calculated between the two separate MRIs. Daily rate of change in the SC volume was calculated assuming an exponential and linear change.

RESULTS

Five of 121 patients (4.13%) demonstrated IPD during SRI, and the incidence was significantly higher in patients undergoing biopsy (vs. surgical resection, 12.9% vs. 1.1%, p=0.015) and in patients with remnant contrast-enhancing tumor after surgery (15.8 vs. 2.0%, p=0.027). The mean daily rate of absolute change in SC was 1.06% (95% confidence interval [CI], 0.89 to 1.23) and 0.89% (95% CI, 0.77 to 1.02) according to the exponential and linear model, respectively. The expected mean volumetric change at 2 weeks were 16.64% (95% CI, 13.77 to 19.52) and 12.51% (95% CI, 10.77 to 14.26), respectively.

CONCLUSION

IPD during the SRI is rare in surgically resected anaplastic gliomas. However, pre-RT MRI is essential for accurate RT-target delineation and disease evaluation for patients initiating RT beyond postoperative 2 weeks and undergoing biopsy, respectively.

Impact of interim progression during the surgery-to-radiotherapy interval and its predictors in glioblastoma treated with temozolomide-based radiochemotherapy

This study was designed to investigate the impact of interim progression of disease (PD) during the surgery-to-radiotherapy interval (SRI) and its predictors in glioblastoma based on MRIs. A total of 222 patients were planned for radiotherapy (RT) and 166 of them were evaluable for the presence of interim PD by 2 separate MRIs. The size criteria from the updated Response Assessment in Neuro-Oncology criteria was adopted to determine interim PD. 32 (19.3%) patients experienced interim PD, and their median survival (MS) was shorter than patients without PD in univariate (11.3 vs. 19.6 months, p < 0.001) and multivariate analysis (HR 2.237, 95% CI 1.367-3.660, p = 0.002). The volume of residual enhancing tumor (p = 0.003) and prolongation of the SRI (p = 0.004) were significant predictors of interim PD. Every 1-cc increase in residual enhancing tumor and every 1-day prolongation of the SRI significantly increased the risk of interim PD by 3.9% (p = 0.003) and 8.1% (p = 0.004), respectively. A significant portion of patients demonstrate interim PD during SRI and these patients have poor prognosis. The presence of interim PD should be concerned as a significant confounding factor for stratification in future clinical trials. A baseline pre-RT MRI is essential for accurate disease evaluation and RT-target delineation, especially in patients with larger residual disease after surgery and prolonged SRI due to the high risk of interim PD.