Send to

Choose Destination
Int J Radiat Oncol Biol Phys. 2008 Dec 1;72(5):1385-95. doi: 10.1016/j.ijrobp.2008.03.007. Epub 2008 May 15.

Effects of interfractional motion and anatomic changes on proton therapy dose distribution in lung cancer.

Author information

Department of Radiation Phyiscs, The University of Texas M. D. Anderson Cancer Center, Houston, TX, USA.



Proton doses are sensitive to intra- and interfractional anatomic changes. We analyzed the effects of interfractional anatomic changes in doses to lung tumors treated with proton therapy.


Weekly four-dimensional computed tomography (4D-CT) scans were acquired for 8 patients with mobile Stage III non-small cell lung cancer who were actually treated with intensity-modulated photon radiotherapy. A conformal proton therapy passive scattering plan was designed for each patient. Dose distributions were recalculated at end-inspiration and end-expiration breathing phases on each weekly 4D-CT data set using the same plans with alignment based on bone registration.


Clinical target volume (CTV) coverage was compromised (from 99% to 90.9%) in 1 patient because of anatomic changes and motion pattern variation. For the rest of the patients, the mean CTV coverage on the repeated weekly 4D-CT data sets was 98.4%, compared with 99% for the original plans. For all 8 patients, however, a mean 4% increase in the volume of the contralateral lung receiving a dose of at least 5 Gy (V5) and a mean 4.4-Gy increase in the spinal cord maximum dose was observed in the repeated 4D-CT data sets. A strong correlation between the CTV density change resulting from tumor shrinkage or anatomic variations and mean contralateral lung dose was observed.


Adaptive re-planning during proton therapy may be indicated in selected patients with non-small cell lung cancer. For most patients, however, CTV coverage is adequate if tumor motion is taken into consideration in the original simulation and planning processes.

[Indexed for MEDLINE]
Free PMC Article

Supplemental Content

Full text links

Icon for Elsevier Science Icon for PubMed Central
Loading ...
Support Center