Assessing radiation exposure of the left anterior descending artery, heart and lung in patients with left breast cancer: A dosimetric comparison between multicatheter accelerated partial breast irradiation and whole breast external beam radiotherapy.
OBJECTIVE
This study aims to quantify dosimetric reduction to the left anterior descending (LAD) artery, heart and lung when comparing whole breast external beam radiotherapy (WBEBRT) with multicatheter accelerated partial breast irradiation (MCABPI) for early stage left breast cancer.


METHODS
Planning CT data sets of 15 patients with left breast cancer receiving multicatheter brachytherapy post breast conserving surgery were used to create two independent treatment plans - WBEBRT prescribed to 50 Gy/25 fractions and MCABPI prescribed to 34 Gy/10 fractions. Dose parameters for (i) LAD artery, (ii) heart, and (iii) ipsilateral lung were calculated and compared between the two treatment modalities.


RESULTS
After adjusting for Equivalent Dose in 2 Gy fractions(EQD2), and comparing MCAPBI with WBEBRT, the largest dose reduction was for the LAD artery whose mean dose differed by a factor of 7.7, followed by the ipsilateral lung and heart with a factor of 4.6 and 2.6 respectively. Compared to WBEBRT, the mean MCAPBI LAD was significantly lower compared to WBEBRT (6.0 Gy vs 45.9 Gy; p<0.01). Mean MCAPBI heart D(0.1cc) (representing the dose received by the most highly exposed 0.1 cc of the risk organ, i.e. the dose peak) was significantly lower (16.3 Gy vs 50.6 Gy; p<0.01). Likewise, the mean heart dose (MHD) was significantly lower (2.3 Gy vs 6.0 Gy; p<0.01). Peak dose and mean lung dose (MLD) for ipsilateral lung was also lower for MCAPBI compared to WBEBRT (Peak dose: 22.2 Gy vs 52.0 Gy; p<0.01; MLD: 2.3 Gy vs 10.7 Gy; p<0.01).


CONCLUSIONS
Compared to WBEBRT, MCAPBI showed a significant reduction in radiation dose for the LAD, heart and lung. This may translate into better cardiac and pulmonary toxicities for patients undergoing MCAPBI.
National University Cancer Institute, Republic of Singapore. Electronic address: tabitha_chan@nuhs.edu.sg.
Tabitha Y
TY
Chan
National University Cancer Institute, Republic of Singapore. Electronic address: poh_wee_tan@nuhs.edu.sg.
Poh Wee
PW
Tan
National University Cancer Institute, Republic of Singapore. Electronic address: chek_wee_tan@nuhs.edu.sg.
Chek Wee
CW
Tan
National University Cancer Institute, Republic of Singapore. Electronic address: johann_tang@nuhs.edu.sg.
Johann I
JI
Tang
D000368:Aged; D001918:Brachytherapy / Q000009:adverse effects / Q000379:methods*; D001943:Breast Neoplasms / Q000532:radiotherapy* / Q000601:surgery; D003331:Coronary Vessels / Q000528:radiation effects; D005260:Female; D006321:Heart / Q000528:radiation effects; D006801:Humans; D008168:Lung / Q000528:radiation effects; D015412:Mastectomy, Segmental / Q000379:methods; D008875:Middle Aged; D000069079:Radiation Exposure / Q000009:adverse effects; D011874:Radiometry; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D014057:Tomography, X-Ray Computed
Dose reduction; Heart; Left anterior descending artery; Lung; Multicatheter accelerated partial breast irradiation; Whole breast external beam radiotherapy