Left-sided breast cancer loco-regional radiotherapy with deep inspiration breath-hold: Does volumetric-modulated arc radiotherapy reduce heart dose further compared with tangential intensity-modulated radiotherapy?
BACKGROUND
Left-sided breast cancer radiotherapy has been associated with an increase in cardiac mortality. This study investigated the potential heart-sparing effect of volumetric-modulated arc radiotherapy (VMAT). We compared VMAT to tangential intensity-modulated radiotherapy (t-IMRT) in the loco-regional treatment of left-sided breast cancer, including internal mammary nodal irradiation, based on deep inspiration breath-hold (DIBH) and free-breathing (FB).


METHODS
Radiotherapy for 15 patients was re-planned. Four plans were compared: t-IMRT-DIBH; VMAT-DIBH; t-IMRT-FB; VMAT-FB. Prescribed dose was 50 Gy in 25 fractions. T-IMRT plans were generated using tangentially orientated fields. VMAT plans were generated using two partial arcs (average arc 190°).


RESULTS
Mean heart dose (MHD) was 5 ± 2.4 Gy, 5.7 ± 1.4 Gy, 9.7 ± 3.3 Gy and 8.1 ± 2.0 Gy for t-IMRT-DIBH, VMAT-DIBH, IMRT-FB and VMAT-FB respectively. The difference in MHD between IMRT-DIBH and VMAT-DIBH was not significant (P = 0.14). VMAT-DIBH significantly spared the volume of heart irradiated to doses of 20 Gy and above (p < 0.05), however, resulted in a significantly higher V5 Gy (P < 0.001), compared to t-IMRT-DIBH. VMAT-DIBH resulted in higher combined lung mean (11 ± 0.8 Gy vs. 8.8 ± 1.1 Gy, P < 0.001) and higher contralateral breast mean dose (5 ± 1 Gy vs. 1.6 ± 1.2 Gy, P < 0.001) compared with t-IMRT-DIBH.


CONCLUSIONS
On average, there was no significant difference in MHD between VMAT-DIBH and t-IMRT-DIBH. However, VMAT-DIBH was found to benefit a select group of patients. For patients in whom the MHD was >6.3 Gy with t-IMRT-DIBH, the use of VMAT-DIBH resulted in a benefit in reducing the MHD.
Department of Radiation Oncology, Crown Princess Mary Cancer Centre Westmead, Sydney, New South Wales, Australia.|Breast Cancer Institute, Westmead, Sydney, New South Wales, Australia.
Trang T
TT
Pham
Department of Radiation Oncology, Crown Princess Mary Cancer Centre Westmead, Sydney, New South Wales, Australia.
Rachel
R
Ward
Department of Radiation Oncology, Crown Princess Mary Cancer Centre Westmead, Sydney, New South Wales, Australia.
Drew
D
Latty
Department of Radiation Oncology, Crown Princess Mary Cancer Centre Westmead, Sydney, New South Wales, Australia.
Catherine
C
Owen
Department of Radiation Oncology, Crown Princess Mary Cancer Centre Westmead, Sydney, New South Wales, Australia.|NHMRC Clinical Trials Centre, University of Sydney, Sydney, New South Wales, Australia.
Val
V
Gebski
Department of Radiation Oncology, Crown Princess Mary Cancer Centre Westmead, Sydney, New South Wales, Australia.
Jacek
J
Chojnowski
Department of Radiation Oncology, Crown Princess Mary Cancer Centre Westmead, Sydney, New South Wales, Australia.
Christopher
C
Kelly
Department of Radiation Oncology, Crown Princess Mary Cancer Centre Westmead, Sydney, New South Wales, Australia.|Breast Cancer Institute, Westmead, Sydney, New South Wales, Australia.|Faculty of Medicine, University of Sydney, Sydney, New South Wales, Australia.
Verity
V
Ahern
Department of Radiation Oncology, Crown Princess Mary Cancer Centre Westmead, Sydney, New South Wales, Australia.|Breast Cancer Institute, Westmead, Sydney, New South Wales, Australia.
Kenneth
K
Tiver
Department of Radiation Oncology, Crown Princess Mary Cancer Centre Westmead, Sydney, New South Wales, Australia.|Breast Cancer Institute, Westmead, Sydney, New South Wales, Australia.
Kirsty
K
Stuart
Department of Radiation Oncology, Crown Princess Mary Cancer Centre Westmead, Sydney, New South Wales, Australia.|Breast Cancer Institute, Westmead, Sydney, New South Wales, Australia.|Faculty of Medicine, University of Sydney, Sydney, New South Wales, Australia.
Wei
W
Wang
D062485:Breath Holding; D005260:Female; D006801:Humans; D058958:Organs at Risk; D011832:Radiation Injuries / Q000517:prevention & control*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D000069584:Unilateral Breast Neoplasms / Q000532:radiotherapy*
IMRT; VMAT; breast cancer; breath-hold; cardiac toxicity