TY - JOUR
T1 - Is Adaptive Treatment Planning Required for Stereotactic Radiotherapy of Stage I Non-Small-Cell Lung Cancer?
AU - Haasbeek, C. J A
AU - Lagerwaard, Frank J.
AU - Cuijpers, Johan P.
AU - Slotman, Ben J.
AU - Senan, Suresh
PY - 2007/4/1
Y1 - 2007/4/1
N2 - Purpose: Changes in position or size of target volumes have been observed during radiotherapy for lung cancer. The need for adaptive treatment planning during stereotactic radiotherapy of Stage I tumors was retrospectively analyzed using repeat four-dimensional computed tomography (4DCT) scans. Methods and Materials: A planning study was performed for 60 tumors in 59 patients using 4DCT scans repeated after two or more treatment fractions. Planning target volumes (PTV) encompassed all tumor mobility, and dose distributions from the initial plan were projected onto PTVs derived from the repeat 4DCT. A dosimetric and volumetric analysis was performed. Results: The repeat 4DCT scans were performed at a mean of 6.6 days (range, 2-12 days) after the first fraction of stereotactic radiotherapy. In 25% of cases the repeat PTV was larger, but the difference exceeded 1 mL in 5 patients only. The mean 3D displacement between the center of mass of both PTVs was 2.0 mm. The initial 80% prescription isodose ensured a mean coverage of 98% of repeat PTVs, and this isodose fully encompassed the repeat internal target volumes in all but 1 tumor. "Inadequate" coverage in the latter was caused by a new area of atelectasis adjacent to the tumor on the repeat 4DCT. Conclusions: Limited "time trends" were observed in PTVs generated by repeated uncoached 4DCT scans, and the dosimetric consequences proved to be minimal. Treatment based only on the initial PTV would not have resulted in major tumor underdosage, indicating that adaptive treatment planning is of limited value for fractionated stereotactic radiotherapy.
AB - Purpose: Changes in position or size of target volumes have been observed during radiotherapy for lung cancer. The need for adaptive treatment planning during stereotactic radiotherapy of Stage I tumors was retrospectively analyzed using repeat four-dimensional computed tomography (4DCT) scans. Methods and Materials: A planning study was performed for 60 tumors in 59 patients using 4DCT scans repeated after two or more treatment fractions. Planning target volumes (PTV) encompassed all tumor mobility, and dose distributions from the initial plan were projected onto PTVs derived from the repeat 4DCT. A dosimetric and volumetric analysis was performed. Results: The repeat 4DCT scans were performed at a mean of 6.6 days (range, 2-12 days) after the first fraction of stereotactic radiotherapy. In 25% of cases the repeat PTV was larger, but the difference exceeded 1 mL in 5 patients only. The mean 3D displacement between the center of mass of both PTVs was 2.0 mm. The initial 80% prescription isodose ensured a mean coverage of 98% of repeat PTVs, and this isodose fully encompassed the repeat internal target volumes in all but 1 tumor. "Inadequate" coverage in the latter was caused by a new area of atelectasis adjacent to the tumor on the repeat 4DCT. Conclusions: Limited "time trends" were observed in PTVs generated by repeated uncoached 4DCT scans, and the dosimetric consequences proved to be minimal. Treatment based only on the initial PTV would not have resulted in major tumor underdosage, indicating that adaptive treatment planning is of limited value for fractionated stereotactic radiotherapy.
KW - Adaptive radiotherapy
KW - Four-dimensional computed tomographic scan
KW - Lung cancer
KW - Planning target volumes
KW - Stereotactic radiotherapy
UR - http://www.scopus.com/inward/record.url?scp=33947547724&partnerID=8YFLogxK
U2 - https://doi.org/10.1016/j.ijrobp.2006.11.018
DO - https://doi.org/10.1016/j.ijrobp.2006.11.018
M3 - Article
C2 - 17275206
SN - 0360-3016
VL - 67
SP - 1370
EP - 1374
JO - International Journal of Radiation Oncology Biology Physics
JF - International Journal of Radiation Oncology Biology Physics
IS - 5
ER -