Comparison of two dimensional and three dimensional radiotherapy treatment planning in locally advanced non-small cell lung cancer treated with continuous hyperfractionated accelerated radiotherapy weekend less.
OBJECTIVE
Patients with inoperable non-small cell lung cancer being treated with continuous hyperfractionated accelerated radiotherapy weekend less (CHARTWEL) were planned and treated with a three dimensional (3D) conformal protocol and comparison made with two dimensional (2D) planning, as used previously, to compare past practice and methods.


METHODS
Twenty-four patients were planned initially using 3D and then replanned using a 2D system. The 2D plans were transferred onto the 3D system and recalculated. Dose volume histograms could then be constructed of planning target volumes for phases 1 and 2 (PTV 1 and 2, respectively), lung and spinal cord for the 2D plans and compared with the 3D plans.


RESULTS
There was a significantly lower absolute dose to the isocentre with 2D compared to 3D planning with dose reductions of 3.9% for phase 1, 4.4% for phase 2 and 4.7% for those treated with a single phase. Maximum dose to spinal cord was greater in 17 of the 24 2D plans with a median dose reduction of 0.82 Gy for 3D (P=0.04). The percentage volume of whole lung receiving > or =20 Gy (V20) was greater in 16 of the 24 2D plans with a median reduction in V20 of 2.4% for 3D (P=0.03).


CONCLUSIONS
A lower dose to tumour was obtained using 2D planning due to the method of dose calculation and spinal cord and lung doses were significantly higher.
Wilson
Elena M
EM
Department of Clinical Oncology, Mount Vernon Cancer Centre, Northwood, Middlesex, HA6 2RN, England, UK.
Joy Williams
Frances
F
Lyn
Basil Ethan
BE
Aird
Edwin G A
EG
D000368:Aged; D002289:Carcinoma, Non-Small-Cell Lung / Q000532:radiotherapy*; D019583:Dose Fractionation, Radiation; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D008175:Lung Neoplasms / Q000532:radiotherapy*; D008297:Male; D008875:Middle Aged; D011832:Radiation Injuries / Q000517:prevention & control; D020266:Radiotherapy, Conformal / Q000379:methods*; D013116:Spinal Cord / Q000528:radiation effects; D016896:Treatment Outcome