Limited benefit of inversely optimised intensity modulation in breast conserving radiotherapy with simultaneously integrated boost.
OBJECTIVE
To examine whether in breast-conserving radiotherapy (RT) with simultaneously integrated boost (SIB), application of inversely planned intensity-modulated radiotherapy (IMRT-SIB) instead of three-dimensional RT (3D-CRT-SIB) has benefits that justify the additional costs, and to evaluate whether a potential benefit of IMRT-SIB depends on specific patient characteristics.


METHODS
3D-CRT-SIB and various IMRT-SIB treatment plans were constructed and optimised for 30 patients with early stage left-sided breast cancer. Coverage of planning target volumes (PTVs) and dose delivered to organs at risk (OARs) were determined for each plan. Overlap between heart and breast PTV (OHB), size of breast and boost PTVs and boost location were examined in their ability to identify patients that might benefit from IMRT-SIB.


RESULTS
All plans had adequate PTV coverage. IMRT-SIB generally reduced dose levels delivered to heart, lungs, and normal breast tissue relative to 3D-CRT-SIB. However, IMRT-SIB benefit differed per patient. For many patients, comparable results were obtained with 3D-CRT-SIB, while patients with OHB>1.4 cm and a relatively large boost PTV volume (>125 cm(3)) gained most from the use of IMRT-SIB.


CONCLUSIONS
In breast-conserving RT, results obtained with 3D-CRT-SIB and IMRT-SIB are generally comparable. Patient characteristics could be used to identify patients that are most likely to benefit from IMRT-SIB.
van der Laan
Hans Paul
HP
Department of Radiation Oncology, University Medical Center Groningen, University of Groningen, The Netherlands. h.p.van.der.laan@rt.umcg.nl
Dolsma
Wil V
WV
Schilstra
Cornelis
C
Korevaar
Erik W
EW
de Bock
Geertruida H
GH
Maduro
John H
JH
Langendijk
Johannes A
JA
D001943:Breast Neoplasms / Q000532:radiotherapy*; D005260:Female; D006801:Humans; D015412:Mastectomy, Segmental; D011879:Radiotherapy Dosage; D050397:Radiotherapy, Intensity-Modulated