Reirradiation with stereotactic body radiotherapy: analysis of human spinal cord tolerance using the generalized linear-quadratic model

Author： Huang Zhibin Mayr Nina A Yuh William T Wang Jian Z Lo Simon S

Publisher： Future Medicine

ISSN： 1479-6694

Source： Future Oncology, Vol.9, Iss.6, 2013-06, pp. : 879-887

Disclaimer: Any content in publications that violate the sovereignty, the constitution or regulations of the PRC is not accepted or approved by CNPIEC.

Previous Menu Next

Abstract

Aim: Using the generalized linear-quadratic (gLQ) model, we reanalyzed published dosimetric data from patients with radiation myelopathy (RM) after reirradiation with spinal stereotactic body radiotherapy (SBRT). Materials & methods: Based on a published study, the thecal sac dose of five RM patients and 14 no RM patients were reanalyzed using gLQ model. Maximum point doses (P_max) in the thecal sac were obtained. The gLQ-based biological effective doses were calculated and normalized (nBED_gLQ) to a 2-Gy equivalent dose (nBED_gLQ = Gy_{2/2_gLQ}). The initial conventional radiotherapy dose, converted to Gy_{2/2_gLQ}, was added. Results: Total (conventional radiotherapy + SBRT) mean P_max nBED_gLQ was lower in no RM than RM patients: 59.2 Gy_{2/2_gLQ} (range: 37.5-101.9) versus 94.8 Gy_{2/2_gLQ} (range: 70.2-133.4) (p = 0.0016). The proportion of total P_max nBED_gLQ accounted for by the SBRT P_max nBED_gLQ was higher for RM patients. No RMs were seen below a total spinal cord nBED_gLQ of 70 Gy_{2/2_gLQ}. Conclusion: The gLQ-derived spinal cord tolerance for total nBED_gLQ was 70 Gy_{2/2_gLQ}.