Table 2 Target volume definitions

GTV

Gross tumor in the bone, including soft tissue extension

Consider fusing diagnostic imaging including PET. MRI is recommended for spinal metastases.

Consider reviewing diagnostic and/or simulation imaging with a diagnostic radiologist.

CTV

Margin for microscopic extension of tumor

GTV + 5 mm but not extending beyond the bone unless direct extension with adjacent tissue invasion is present.

NOTE: For lesions in the spine undergoing SBRT, published guidelines will be followed [24]

PTV

Margin for setup error (patient positioning and treatment delivery)

CTV + 3 mm (if using daily CBCT)