Dosimetric evaluation of a conformal seven-field coplanar technique for planning lung stereotactic body radiotherapy

To assess the effectiveness of a seven-field coplanar planning technique in producing dosimetrically acceptable treatment plans when measured against the dose constraints of the ROSEL trial quality assurance working party.

Nineteen patients with non-small cell lung cancer staged at T1-T2 underwent computed tomography scanning in preparation for lung stereotactic body radiotherapy treatment. Planning target volumes ranged from 17 to 100 cm(3). Dose plans were created with the enhanced collapsed cone algorithm on the Oncentra Masterplan treatment planning system using an open-field conformal coplanar technique. The plan acceptance criteria in the ROSEL study protocol were used for critical evaluation of the plans to determine their suitability for clinical use.

Clinically acceptable plans were produced for 17 of the 19 patients with no more than two minor dosimetric deviations from protocol. The two patients where conflicts between adequate tumour coverage and unacceptably high doses to surrounding tissue could not be reconciled were characterised by low average Hounsfield Unit values in the planning target volume, i.e. less than about -700 Hounsfield Units. This tissue density was comparable with that of the surrounding healthy lung tissue.

This planning technique produces clinically acceptable plans for most lung stereotactic body radiotherapy patients without the need to resort to more complex methods of treatment planning and delivery.