On the cutting edge of intensity modulated radiotherapy and simultaneous integrated boost (IMRT-SIB): The case of a patient with 8 brain metastases.

Background: Patients with multiple brain metastases, especially those with more than 3 lesions, usually undergo to palliative whole brain (WB) radiotherapy (RT).

Methods: A breast cancer patient with 8 brain metastases was treated on the brain by a radical RT regimen. Prescription doses were according to the simultaneous integrated boost-intensity modulated radiation therapy (SIB-IMRT) technique with all lesions as well brain irradiated simultaneously in 20 daily fractions. Doses of 40.0 Gy (2.0 Gy/fraction) and 50.0 Gy (2.5 Gy/fraction) were prescribed to the whole brain and to eight individual metastases, respectively.

Results: Mean volume of the eight metastases was 8.1 cc (range: 3.8-10.1 cc). For all lesions, the volume receiving 95% of prescribed dose was 100% and dose homogeneity was within 3%. Moreover, maximum doses were less than 105% of prescribed dose, while average mean dose to lesions was 50.6 Gy (range: 49.7-51.5 Gy). Whole brain mean dose was 45.2 Gy. Maximum doses to brainstem and optic chiasma were limited to 44.5 Gy and 42.9 Gy, respectively, while maximum doses to eyes, lens and optic nerves were limited to 9.2 Gy, 4.9 Gy and 41.0 Gy, respectively. From a clinical point of view, subsequent MRI brain controls showed a complete clinical response. Forty months after treatment the patient is disease free and shows no late brain and skin toxicities.

Conclusion: This case demonstrates the technical feasibility of a SIB-IMRT treatment in patients with more than 3 brain metastases.