Radiation dose response for supratentorial low-grade glioma—institutional experience and literature review $ Simon S. Lo a, * , Walter A. Hall b , Kwan H. Cho a , Jamie Orner a , Chung K. Lee a , Kathryn E. Dusenbery a a Department of Therapeutic Radiology-Radiation Oncology, Fairview University Medical Center, University of Minnesota, Minneapolis, MN, USA b Department of Neurosurgery, Fairview University Medical Center, University of Minnesota, Minneapolis, MN, USA Received 25 February 2003; received in revised form 6 May 2003; accepted 27 May 2003 Abstract Purpose: To examine radiation dose response for low-grade glioma (LGG) based on our institutional experience and to review the literature on this topic. Methods and Materials: Sixty-seven patients with supratentorial low-grade nonpilocytic astrocytomas (n = 36) or oligodendrogliomas (n =31) were treated with postoperative radiation therapy (RT). Twenty-seven patients (group A) received 5520 cGy; 24 patients (group B) received 5940 cGy; and 16 patients (group C) received 6375 cGy. The corresponding median follow-up was 60, 35 and 91 months, respectively. Results: The disease-specific survival (DSS) at 5 and 10 years were 90.2% and 56.2%, 67.6% and 47.3%, and 62.5% and 50% for groups A, B and C, respectively ( P = 0.40). Only a greater extent of surgical resection and absence of contrast enhancement predicted DSS on multivariate analyses. Patients receiving higher doses of RT had higher complication rates. Conclusion: Our data confirmed the lack of radiation dose response for supratentorial LGG as demonstrated in the previous randomized trials. The radiation dose should not exceed 5520 cGy because dose escalation did not result in an improvement of DSS and it also increased the complication rates. Future research should focus on the eradication of radioresistant clones either by the improvement of surgical resection or the use of cytotoxic agents that can target on the radioresistant tumor cells. D 2003 Elsevier B.V. All rights reserved. Keywords: Radiotherapy; Dose response; Low-grade glioma 1. Introduction Low-grade gliomas (LGG) constitute 15% of all adult brain tumors. Surgical resection is regarded as the standard treatment for these tumors. While World Health Organi- zation (WHO) grade I tumors are associated with favor- able treatment outcomes after surgical resection, WHO grade II tumors carry a much worse prognosis [1,2]. To improve the treatment outcome of these tumors, postop- erative radiation therapy (RT) is frequently utilized after surgical resection [3]. From a radiobiological standpoint, a higher radiation dose should result in a higher tumor cell kill and hence better tumor control. However, two ran- domized trials showed no radiation dose response for LGG [2,4]. Here, we attempt to revisit the issue of radiation dose response for supratentorial nonpilocytic low-grade glioma in our cohort of patients with long-term follow-up at our institution and to review the literature on this topic. 2. Methods and materials From the database of our radiation oncology clinic, we have identified 67 patients (35 male and 32 female) with supratentorial low-grade nonpilocytic astrocytomas (n = 36) or oligodendrogliomas (n = 31) (WHO grade II tumors) treated with postoperative radiation therapy from January 1984 to April 2000. All patients had radiologic imaging with computerized tomography (CT) or magnetic resonance imaging (MRI) and pathologic diagnoses. All the neuropa- thology slides were read by two neuropathologists in our 0022-510X/03/$ - see front matter D 2003 Elsevier B.V. All rights reserved. doi:10.1016/S0022-510X(03)00181-3 $ This paper was presented at the Annual Meeting of the Radiological Society of North America Meeting in Chicago, IL, in December 2002. There were no grants or financial support associated with this study. * Corresponding author. Department of Radiation Oncology, Loyola University Medical Center, Building 105, Ste 2944, 2160 S. First Avenue, Maywood, IL 60153, USA. Tel.: +1-708-2162557; fax: +1-708-2164498. E-mail addresses: smlo@hotmail.com, slo@lumc.edu (S.S. Lo). www.elsevier.com/locate/jns Journal of the Neurological Sciences 214 (2003) 43 – 48