Correlation of Local Failure With Measures of Dose Insufficiency in the High-Dose Single-Fraction Treatment of Bony Metastases

Abstract

Purpose In the setting of high-dose single-fraction image-guided radiotherapy of spine metastases, the delivered dose is hypothesized to be a significant factor in local control. We investigated the dependence of local control on measures of dose insufficiency. Methods and Materials The minimum doses received by the hottest 100%, 98%, and 95% (Dmin, D98, and D95) of the gross target volume (GTV) were computed for 91 consecutively treated lesions observed in 79 patients. Prescribed doses of 18–24 Gy were delivered in a single fraction. The spinal cord and cauda equina were constrained to a maximum dose of 12–14 Gy and 16 Gy, respectively. A rank-sum test was used to assess the differences between radiographic local failure and local control. Results With a median follow-up of 18 months, seven local failures have occurred. The distributions of GTV Dmin, D98, and D95 for treatments resulting in local failure were found to be statistically different from the corresponding distributions of the patient group as a whole. Taking no account of histology, p values calculated for Dmin, D98, and D95 were 0.004, 0.012, and 0.031, respectively. No correlations between local failure and target volume or between local failure and anatomic location were found. Conclusions The results indicate that Dmin, D98, and D95 may be important risk factors for local failure. No local failures in any histology were observed when Dmin was >15 Gy, suggesting that this metric may be an important predictor of local control.

Local disease control for spinal metastases following “separation surgery” and adjuvant hypofractionated or high-dose single-fraction stereotactic radiosurgery: outcome analysis in 186 patients

“…7 The difference in tumor arrest mechanisms may account for the finding that SRS provides improved local tumor control irrespective of histology and size, which differs from the results observed with conventional fractionation. 4,19,28,30 Because SRS provides local tumor control irrespective of the tumor volume, the extent of tumor resection loses importance as long as there is adequate separation of the tumor from vital structures to allow for optimal radiation dosimetry.…”

Commissioning and initial stereotactic ablative radiotherapy experience with Vero

“…Initial clinical results from prospective single institution, and more recently, multi‐institutional clinical trials of SABR have documented high rates of tumor control coupled with a low incidence of serious toxicity despite the high‐dose fractions of radiation being delivered. In the setting of early stage lung cancer, three‐year local control rates of 88% to 97% have been reported 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 …”

Clinical practice of image-guided spine radiosurgery - results from an international research consortium

“…even the "high dose" approach of 40 Gy in 20 fractions would result in tumor control of less than 5% for NSCLC [33]. This hypothesis is supported by three studies, which reported a significant dose response relationship for primary [17,31] and re-irradiation [34] spine radiosurgery. The Memorial Sloan-Kettering Cancer Center (MSMCC) group reported excellent local control of > 95% for a prescription dose of 24 Gy and a minimum dose of > 15.1 Gy; however, the results are based on a retrospective review of serially dose-escalated patients and require validation before conclusions can be drawn.…”