The influence of respiratory motion on dose distribution in accelerated partial breast irradiation using volumetric modulated arc therapy

Abstract

Accelerated partial breast irradiation (APBI) is alternative treatment option for patients with early stage breast cancer. The interplay effect on volumetric modulated arc therapy APBI (VMAT-APBI) has not been clarified. This study aimed to evaluate the feasibility of VMAT-APBI for patients with small breasts and investigate the amplitude of respiratory motion during VMAT-APBI delivery that significantly affects dose distribution. Methods: The VMAT-APBI plans were generated with 28.5 Gy in five fractions. We performed patient-specific quality assurance using Delta 4 phantom under static conditions. We also measured point dose and dose distribution using the ionization chamber and radiochromic film under static and moving conditions of 2, 3 and 5 mm. We compared the measured and calculated point doses and dose distributions by dose difference and gamma passing rates. Results: A total of 20 plans were generated; the dose distributions were consistent with those of previous reports. For all measurements under static conditions, the measured and calculated point doses and dose distributions showed good agreement. The dose differences for chamber measurement were within 3%, regardless of moving conditions. The mean gamma passing rates with 3%/2 mm criteria in the film measurement under static conditions and with 2 mm, 3 mm, and 5 mm of amplitude were 95.0 ± 2.0%, 93.3 ± 3.3%, 92.1 ± 6.2% and 84.8 ± 7.8%, respectively. The difference between 5 mm amplitude and other conditions was statistically significant. Conclusions: Respiratory management should be considered for the risk of unintended dose distribution if the respiratory amplitude is >5 mm.

Residual Image Registration Error by Fiducial Markers in Accelerated Partial Breast Irradiation Using C-Arm Linac: A Phantom Study

“…Yamauchi et al investigated the amplitude of the respiratory motion during VMAT-APBI delivery, which signi cantly affects dose distribution, and recommended considering respiratory motion management (e.g., breath-hold and shallow breathing) if the amplitude is >5 mm [10]. We believe that treatment during free breathing is reasonable and the feasibility of nongated IGRT during a single fraction was veri ed.…”

“…Yue et al reported that the phase difference uncertainty in the respiratory cycle between images is considered insigni cant due to the fact that the respiration induced target movement is relatively small [21]. In previous studies examining respiratory motion of the breast, the mean ± SD of the respiratory motion in the LR, SI, and AP directions were 0.5 ± 0.6 mm, 1.7 ± 1.3 mm, and 2.3 ± 1.8 mm in the study by Yamauchi et al [10] and 1.0 ± 0.6 mm, 1.3 ± 0.5 mm, and 2.6 ± 1.4 mm in the study by Kinoshita et al [25].…”

“…The percentage of patients with a vertical amplitude of 3.1-5.0 mm and >5.0 mm was 8% and 12%, respectively [10]. Because the patients who exhibited amplitudes of 3 and 5 mm had a certain probability, we investigated the effect based on these amplitudes.…”

“…Several studies on the long-term e cacy of external beam accelerated partial breast irradiation (APBI) are currently being conducted and have demonstrated an outcome comparable to standard whole breast irradiation after breast conservation surgery [4][5][6][7][8][9]. To increase the dose homogeneity and conformity at the target and improve cosmesis, APBI with intensitymodulated radiation therapy or volumetric modulated arc therapy (VMAT) has been used in some clinical trials [8][9][10]. APBI requires more positional accuracy than whole breast irradiation as it involves delivering a high dose in hypofractions to a relatively small area.…”

Is it advantageous to use deep inspiration breath hold (DIBH) over free breathing for FAST-Forward dose fractionation scheme in treating carcinoma of left-sided breast? A dosimetric study

“…8 Hence, in DIBH, dose can be delivered as per plan to critical structures as well as PTV compared to FB. 23 This phenomenon should be weighed high when we are delivering high dose per fraction of few fractions (1-5 fractions).…”