Comparisons of static 7 field and dynamic conformal arc techniques for stereotactic lung radiotherapy

METHODS

Treatment of 33 lung tumors was planned using DCA or S7F
techniques, and tumors were allocated into groups according
to their volume (small: <25 cc, medium: 25-50 cc, large: >50
cc) and localization (central, peripheral). Plans were compared
in terms of lung volume receiving 5 Gy (V₅), spinal cord maximum
dose (spinal D_max), homogeneity index (HI), and monitor-
unit (MU) parameters.

RESULTS

No statistical difference was shown in RTOG criteria. HI was
lower with DCA (p=0.018) while V₅, spinal D_max and MU
were lower with S7F (p=0.007, p=0.001, p<0.001, respectively).
With the S7F technique, spinal Dmax in small tumors,
V₅, spinal Dmax and MU in medium tumors, V₅ and MU in
large tumors, V₅ and spinal Dmax in central tumors, and spinal
Dmax and MU in peripheral tumors were lower.

CONCLUSION

Spinal D_max, V₅ and MU were better with the S7F technique.
Both techniques are appropriate for planning according to
RTOG criteria.

Keywords: Lung cancer; radiotherapy; stereotactic radiotherapy