Multisegmented tangential breast fields: a rational way to treat breast cancer.
OBJECTIVE
Using three-dimensional conformal radiation therapy (3D-CRT) and multisegmented conformal radiation therapy (MS-CRT) for breast cancer treatment, the dose coverage of the planning target volume (PTV) and the radiation burden on the organs at risk (OARs) were evaluated.


METHODS
3D-CRT and MS-CRT were planned for 436 unilateral breasts (217 left). All patients were treated with MS-CRT between 2005 and 2007. For PTV delineation and beam orientation, supportive structures were applied. The mean PTV was 1,130 cm3 (in ten patients > 2,200 cm3). Three-dimensional planning with weight-optimized medial and lateral open fields at a total dose of 50.4/1.8 Gy was followed by multisegmented planning with a reasonably high-dose-level dose cloud to define the medial subfield, and renewed optimization. This was repeated for the lateral subfield with a final optimization. For PTV coverage evaluation, the ICRU 50 was considered: the PTV portions receiving 95-107%, < 95% and > 107% of the prescribed dose (PTVD95- 107%, PTV<D95% and PTV>D107%), and the PTV maximal dose (PTVDmax). To compare the OAR radiation burdens, the mean doses to the ipsi-/contralateral lung, contralateral breast, and whole heart were documented.


RESULTS
The multisegmented plans furnished significantly (p < 0.0001) better target coverage (PTVD95-107% 82.8% vs. 90.9%, PTV<D95% 11.4% vs. 8.8%, PTV>D107% 5.9% vs. 0.3% and PTVDmax 56.6 vs. 54.3 Gy). The mean OAR doses remained almost unchanged: ipsilateral lung 10.5 versus 10.4 Gy, contralateral lung 0.4 versus 0.4 Gy, contralateral breast 0.8 versus 0.8 Gy, and whole heart (for left-sided cancers) 4.8 versus 4.8 Gy. The subfields required a mean of 9.8 MU (monitor units), i.e., a mean total 7.6 MU increment. The planning took 10-20 min, and the delivery 5-10 min.


CONCLUSIONS
MS-CRT is a good alternative to breast intensity-modulated radiation therapy (IMRT) and seems adequate for right-sided cancers, whereas left-sided cancers necessitate a longer follow-up of heart-related side effects before a final assessment.
Gulybán
Akos
A
Department of Oncotherapy, University of Pécs, Hungary. akos.gulyban@gmail.com
Kovács
Péter
P
Sebestyén
Zsolt
Z
Farkas
Róbert
R
Csere
Tibor
T
Karácsonyi
Gábor
G
Dérczy
Katalin
K
Hideghéty
Katalin
K
Esik
Olga
O
D001822:Body Burden; D001940:Breast / Q000528:radiation effects; D001943:Breast Neoplasms / Q000532:radiotherapy*; D005260:Female; D006321:Heart / Q000528:radiation effects; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008168:Lung / Q000528:radiation effects; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D020266:Radiotherapy, Conformal / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D014057:Tomography, X-Ray Computed / Q000379:methods*