Dose Constraints in Head and Neck Reirradiation

Critical Principles

The American Society of Radiation Oncology recommends that radiation plans must be based on accurate reconstruction of the previous RT dose distribution, taking into account expected morbidity of additional radiation 1, 2, 3
The degree of recovery from initial radiation is difficult to estimate and varies by organ, and the National Comprehensive Cancer Network suggests that this should be considered when planning reirradiation 1, 2, 3

If a new course of high-dose RT can be delivered without exceeding estimated dose constraints on organs at risk, the European Society for Radiotherapy and Oncology recommends treating with the same intent and approach as a radiation-naïve recurrence 1, 2, 4, 5
The American College of Radiology suggests that low-dose reirradiation with palliative intent is appropriate only if it can be performed with negligible risk of toxicity 1, 2, 4

Particular caution is warranted in reirradiating the carotid artery, as severe, life-threatening complications such as carotid blowout syndrome have been reported, according to the American Heart Association 1, 2, 4, 5, 3
The National Comprehensive Cancer Network recommends that the maximum dose to the spinal cord should be limited to 50 Gy with conventional fractionation for initial treatment 3

The American Society for Radiation Oncology recommends delivering at least 74 GyE using conventional fractionation for photon and proton therapy when previous RT was not to the same area 1, 2, 5
The National Comprehensive Cancer Network suggests that no optimal dose and fractionation scheme is established for reirradiating previously treated areas, and radiotherapists must exercise professional judgment 1, 2, 4, 5

The European Society for Radiotherapy and Oncology recommends not assuming complete tissue recovery from initial radiation, as the degree of recovery varies by organ 1, 2, 3
The American College of Radiology suggests not proceeding with reirradiation without accurate reconstruction of previous dose distribution 3
The American Society for Radiation Oncology recommends considering the timing between treatments, as the time interval between radiation treatments is a key factor for limiting toxicity 1, 2, 4

The American Society of Clinical Oncology recommends summing the cumulative doses to brainstem and spinal cord from both treatment courses when available, to ensure accurate planning for reirradiation 6

The National Comprehensive Cancer Network suggests applying similar conservative cumulative dose limits to the cerebellum as to the brainstem, given proximity to brainstem and shared neurotoxicity concerns 7
The American Society of Clinical Oncology notes that neurocognitive deficits can occur when CNS structures are within the radiation field, compounded by chemotherapy effects 7

For spinal metastases undergoing reirradiation with SBRT, the American College of Radiology recommends targeting a BED₁₀ of at least 100 Gy for optimal local control, using regimens such as 16-24 Gy in 1 fraction, 24 Gy in 2 fractions, or 24-27 Gy in 3 fractions, which achieve approximately 90% 1-year local control and 54% complete pain response in patients with spinal metastases 8

For renal cell carcinoma spinal metastases, a dose of 24 Gy in a single fraction using simultaneous integrated boost technique has been employed successfully, achieving 90% 2-year local control, according to the National Comprehensive Cancer Network guidelines 8