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Int J Radiat Oncol Biol Phys. 2006 Dec 1;66(5):1446-9. Epub 2006 Nov 2.

Update of human spinal cord reirradiation tolerance based on additional data from 38 patients.

Author information

1
Department of Radiation Oncology, Klinikum Rechts der Isar der Technischen Universit√§t M√ľnchen, Munich, Germany. cnied@hotmail.com

Abstract

PURPOSE:

To update a combined analysis of all published clinical data.

METHODS AND MATERIALS:

We collected data from 38 additional patients treated in our department or published in four different reports and calculated the biologically effective dose (BED) according to the linear-quadratic model using an alpha/beta value of 2 Gy for cervical and thoracic cord and 4 Gy for lumbar cord. In this model, a dose of 50 Gy given in single daily fractions of 2 Gy is equivalent to a BED of 100 Gy(2) or 75 Gy(4).

RESULTS:

The 2005 risk score based on three variables (cumulative BED, highest BED of all treatment series in a particular individual, and interval), which discriminate three different risk groups, does not require modification. The low-risk group now contains 1 case of radiation myelopathy (RM) after hypofractionated stereotactic reirradiation. Therefore, the rate increased from 0% to 3%. Intermediate-risk patients developed RM in 25%, and high-risk patients in 90%. When the interval between the two treatment courses is not shorter than 6 months and the dose of each course is < or =98 Gy(2), the cumulative BED where no case of RM has yet been reported is 120 Gy(2).

CONCLUSIONS:

Based on these updated results, the risk of RM appears small after < or =135.5 Gy(2) when the interval is not shorter than 6 months and the dose of each course is < or =98 Gy(2). We would recommend limiting the dose to the lowest feasible level. The influence of very steep dose gradients from stereotactic and intensity-modulated approaches (i.e., a more complex volume-effect) requires further evaluation.

PMID:
17084560
DOI:
10.1016/j.ijrobp.2006.07.1383
[Indexed for MEDLINE]
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