D.K. Fujimoto

A Phase I/II Trial of 5 Fraction Stereotactic Radiosurgery With 5-mm Margins With Concurrent and Adjuvant Temozolomide in Newly Diagnosed Supratentorial Glioblastoma Multiforme.

The spine cases included a fifth lumbar spine (case 1), fifth thoracic spine (case 2), and 10th thoracic spine metastases (case 3). Targets and organs at risk (OAR) were contoured by one experienced radiation oncologist according to International Spine Radiosurgery Consortium Consensus Guidelines and a 2 mm planning target volume (PTV) applied. The DICOM files were sent to each institute for planning. The treatment planning guidelines in the previous study included, prescribed dose of 24 Gy in two fractions with more than 70% prescribed dose to encompass D95, D0.035 <140% of the prescribed dose, and a maximum dose to the spinal cord planning organ at risk volume (PRV) or thecal sac <17 Gy. New guidelines added (D95 should be as high as possible (AHAP), D50 should be between 110% and 115% of prescribed dose and AHAP and D0.035 should be between 125% and 135% of the prescribed dose). The dose volume histograms (DVHs) were centrally reviewed. Results: In our previous study the PTV D95 ranged from 70.0% to 99.6% in case 1 (mean SD; 21.21 2.43 Gy), 70.4% to 98.8% in case 2 (20.32 2.22 Gy), and 70.0% to 94.2% in case 3 (19.78 1.97 Gy), respectively, and D50 for PTV ranged from 99.2% to 116.3% in case 1 (25.62 1.34 Gy), 91.7% to 119.6% in case 2 (25.97 2.18 Gy) and 84.2% to 114.2% in case 3 (25.57 2.14 Gy), respectively. In this study PTV D95 ranged from 80.4% to 100.0% in case 1 (21.96 1.67 Gy), 76.3% to 95.8% in case 2 (20.91 1.67 Gy), and 70.4% to 94.2% in case 3 (20.3 1.86 Gy), respectively and D50 for PTV ranged from 109.6% to 115.4% in case 1 (27.02 0.53 Gy), 110.0% to 117.5% in case 2 (27.06 0.63 Gy) and 107.5% to 115.0% in case 3 (26.89 0.67 Gy), respectively. Conclusion: We succeeded to minimize the inter-institutional variations. This study highlights dose constraints of D95, D50, and D0.035 should be used to minimize the variations. Author Disclosure: H. Tanaka: None. T. Furuya: None. Y. Kumazaki: None. M. Nakayama: None. H. Nishimura: None. M.E. Ruschin: None. D. Pinnaduwage: None. J. Phua: None. I. Thibault: None. J. StHilaire: None. L. Ma: None. A. Sahgal: None. N. Shikama: None. K. Karasawa: None.

Newly diagnosed glioblastoma: adverse socioeconomic factors correlate with delay in radiotherapy initiation and worse overall survival

Abstract The optimal time for starting radiation in patients with glioblastoma (GBM) is controversial. We aimed to evaluate postoperative radiotherapy treatment patterns and the impact of timing of radiotherapy on survival outcomes in patients with GBM using a large, national hospital-based registry in the era of Stupp chemoradiation. We performed a retrospective cohort study using the National Cancer Data Base and identified adults with GBM diagnosed between 2010 and 2013 and treated with chemoradiation. We classified time from surgery/biopsy to radiation start into the following categories: <15 days, 15–21 days, 22–28 days, 29–35 days, 36–42 days and >42 days. We assessed the relation between time to radiation start and survival using Cox proportional hazards modeling adjusting for clinically relevant variables that were selected a priori. We used multivariate logistic modeling to determine factors independently associated with receipt of delayed radiation treatment. A total of 12 738 patients met our inclusion criteria after our cohort selection process. The majority of patients underwent either gross total (n = 5270, 41%) or subtotal (n = 4700, 37%) resection, while 2768 patients (22%) underwent biopsy only. Median time from definitive surgery or biopsy to initiation of radiation was 29 days (interquartile range 24–36 days). For patients who had biopsy or subtotal resection, earlier initiation of radiation did not appear to be associated with improved survival. However, among patients who underwent gross total resection, there appeared to be improved survival with early initiation of radiation. Patients who initiated radiation within 15–21 days of gross total resection had improved survival (hazard ratio 0.82, 95% confidence interval 0.69–0.98, P = 0.03) compared with patients who had delayed (>42 days after surgery) radiation. There was also a trend (P = 0.07 to 0.12) for improved survival for patients who initiated radiation within 22–35 days of gross total resection compared with patients who had delayed radiation. Patients who were black, had Medicaid or other government insurance or were not insured, and who lived in metropolitan areas or further away from the treating facility had higher odds of receiving radiation >35 days after gross total resection. Patients who lived in higher income areas had higher odds of receiving radiation within 35 days of a gross total resection. In a large cohort of patients with GBM treated with chemoradiation, our data suggest a survival benefit in initiating radiotherapy within 35 days after gross total resection. Further research is warranted to understand barriers to timely access to optimal therapy.

Stereotactic Radiosurgery for Skull Base Chordomas and Chondrosarcomas

Abstract Chordomas are slow-growing tumors of bone thought to arise in notochord remnants. They are rare, locally aggressive, and infiltrative tumors that can occur anywhere along the axial skeleton. Optimal surgery is often unattainable and multimodality treatment, which includes radiotherapy, is usually indicated. However, despite high-dose radiotherapy, tumors frequently recur. Local recurrence is the harbinger to mortality, through local progression or metastatic disease. There are currently no guidelines regarding the best management of recurrent chordoma. Stereotactic radiosurgery holds the promise to improve local control through its ability to escalate dose. Further research is needed to define the optimal patient selection, ideal dose, and target volume, and determine normal tissue tolerance for single or hypofractionated stereotactic radiosurgery.

The Role of Stereotactic Radiosurgery in the Reirradiation of Metastatic Spinal Tumors

The spine cases included a fifth lumbar spine (case 1), fifth thoracic spine (case 2), and 10th thoracic spine metastases (case 3). Targets and organs at risk (OAR) were contoured by one experienced radiation oncologist according to International Spine Radiosurgery Consortium Consensus Guidelines and a 2 mm planning target volume (PTV) applied. The DICOM files were sent to each institute for planning. The treatment planning guidelines in the previous study included, prescribed dose of 24 Gy in two fractions with more than 70% prescribed dose to encompass D95, D0.035 <140% of the prescribed dose, and a maximum dose to the spinal cord planning organ at risk volume (PRV) or thecal sac <17 Gy. New guidelines added (D95 should be as high as possible (AHAP), D50 should be between 110% and 115% of prescribed dose and AHAP and D0.035 should be between 125% and 135% of the prescribed dose). The dose volume histograms (DVHs) were centrally reviewed. Results: In our previous study the PTV D95 ranged from 70.0% to 99.6% in case 1 (mean SD; 21.21 2.43 Gy), 70.4% to 98.8% in case 2 (20.32 2.22 Gy), and 70.0% to 94.2% in case 3 (19.78 1.97 Gy), respectively, and D50 for PTV ranged from 99.2% to 116.3% in case 1 (25.62 1.34 Gy), 91.7% to 119.6% in case 2 (25.97 2.18 Gy) and 84.2% to 114.2% in case 3 (25.57 2.14 Gy), respectively. In this study PTV D95 ranged from 80.4% to 100.0% in case 1 (21.96 1.67 Gy), 76.3% to 95.8% in case 2 (20.91 1.67 Gy), and 70.4% to 94.2% in case 3 (20.3 1.86 Gy), respectively and D50 for PTV ranged from 109.6% to 115.4% in case 1 (27.02 0.53 Gy), 110.0% to 117.5% in case 2 (27.06 0.63 Gy) and 107.5% to 115.0% in case 3 (26.89 0.67 Gy), respectively. Conclusion: We succeeded to minimize the inter-institutional variations. This study highlights dose constraints of D95, D50, and D0.035 should be used to minimize the variations. Author Disclosure: H. Tanaka: None. T. Furuya: None. Y. Kumazaki: None. M. Nakayama: None. H. Nishimura: None. M.E. Ruschin: None. D. Pinnaduwage: None. J. Phua: None. I. Thibault: None. J. StHilaire: None. L. Ma: None. A. Sahgal: None. N. Shikama: None. K. Karasawa: None.