Repeat reirradiation of the spinal cord: multi-national expert treatment recommendations

Improved survival of patients with spinal bone metastases has resulted in an increased number of referrals for retreatment and repeat reirradiation. A consortium of expert radiation oncologists (RO) has been established with the aim of providing treatment recommendations for challenging clinical scenarios for which there are no established guidelines. In this case, a patient developed local progression of a T5 vertebral lesion after two prior courses of palliative radiotherapy (time interval > 12 months, assumed cumulative biologically equivalent dose in 2aEuroGy fractions [EQD2] for spinal cord [alpha/beta 2aEuroGy] 75aEuroGy). Expert recommendations were tabulated with the aim of providing guidance. Five of seven RO would offer a third course of radiotherapy, preferably with advanced techniques such as stereotactic radiotherapy. However, the dose-fractionation concepts were heterogeneous (3-20 fractions) and sometimes adjusted to different options for systemic treatment. All five RO would compromise target volume coverage to reduce the dose to the spinal cord. Definition of the spinal cord planning-organ-at-risk volume was heterogeneous. All five RO limited the EQD2 for spinal cord. Two were willing to accept more than 12.5aEuroGy and the highest EQD2 was 19aEuroGy. The increasing body of literature about bone metastases and spinal cord reirradiation has encouraged some expert RO to offer palliative reirradiation with cumulative cord doses above 75aEuroGy EQD2; however, no consensus was achieved. Strategies for harmonization of clinical practice and development of evidence-based dose constraints are discussed