Breast Cancer

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TU_10_3415 - A Within Subject Study Comparing Utility and Comfort of Breast Board Immobilization with Vacuum Bag for Radiation Therapy in Breast Cancer

Tuesday, October 23
2:45 PM - 4:15 PM
Location: Innovation Hub, Exhibit Hall 3

A Within Subject Study Comparing Utility and Comfort of Breast Board Immobilization with Vacuum Bag for Radiation Therapy in Breast Cancer
S. Sundar1, B. K. Sasidharan2, S. S. Varghese2, E. S. Sam Jeyakumar3, S. Annamalai2, P. S. Premkumar4, R. R. Singh3, and S. Backianathan2; 1Apollo Speciality Hospitals, Department of Radiation Oncology, Chennai, India, 2Christian Medical College, Department of Radiation Oncology, Vellore, Tamil Nadu, India, 3Christian Medical College, Medical Physics, Vellore, Tamil Nadu, India, 4Christian Medical College, Department of Biostatistics, Vellore, Tamil Nadu, India

Purpose/Objective(s): Immobilization for breast cancer radiotherapy can be achieved using either Breast board (BB) or vacuum bag (VB). A prospective observational study was conducted to evaluate setup precision, patient comfort and treatment time between the two methods in supine position breast/chest-wall radiotherapy. A within subject design was used to negate the effect of confounding factors influencing setup precision.

Materials/Methods: Twenty-two patients recruited to the study underwent planning CT with BB and VB immobilization independently. Plans were generated delivering the same dose to the target volumes on each planning CT. Both the plans were evaluated independently and modified to be comparable with respect to target coverage and normal tissue dose. Patients who had comparable plans underwent radiotherapy with BB and VB immobilization in a daily alternating schedule. Setup errors along x, y and z axes were recorded using CBCT imaging. Median systematic error (MSE) and mean random error (MRE) for each immobilization device was calculated. The time needed for setup, the beam-on time, and in-room time were recorded. A questionnaire was used to record the patient’s preference and comfort on a weekly basis. Non-parametric and parametric testing were used to statistically correlate the differences in median systematic error and mean random error respectively. Paired t-test was used compare the difference in setup duration.

Results: A comparable plan was achieved in 16 of 22 patients for VC to BB. A total of 239 CBCT acquisitions were analysed for 16 patients. 117 translational errors in x, y and z axes with BB immobilisation and 122 with VB immobilisation were recorded. MRE (0.43 ± 0.19 vs 0.41 ± 0.21 cm and 0.46 ± 0.18 vs 0.44 ± 0.18 cm) and MSE (IQR) [0.2 (0.1,0.4) vs 0.3 (0.2,0.5) cm and 0.3 (0.2,0.4) vs 0.2 (0.1,0.3) cm] were not significantly different between BB and VB in x or y axes respectively. Mean random error in z-axis was lesser with VB (0.36 ± 0.13 vs 0.51 ± 0.23 cm, p = 0.03) than BB. The magnitude of difference in MRE along z-axis was higher favouring a vacuum bag among overweight (n=5, 0.52 ± 0.08 vs 0.28 ± 0.14 cm) and obese patients (n=4, 0.72 ± 0.35 vs 0.45 ± 0.10 cm). From the comfort questionnaire responses, 68% patients preferred to use a VB. The mean setup duration was longer with BB (8.2 ± 2.2 min) than with VB (7.2 ± 1.2 min, p = 0.03).

Conclusion: Target coverage and optimal plan was achieved in more patients with BB immobilization compared to VB. However, VB immobilization showed lesser random errors in longitudinal directions as compared to BB immobilization. VB may be preferred over use of BB among overweight and obese patients.
n(16)

MSE (IQR) in cm

MRE (SD) in cm

X

Y

Z

X

Y

Z

BB

0.2 (0.1,0.4)

0.3 (0.2,0.4)

0.3 (0.2,0.4)

0.43 (0.19)

0.46 (0.18)

0.51 (0.23)

VB

0.3 (0.2,0.5)

0.2 (0.1,0.3)

0.3 (0.2,0.5)

0.41 (0.21)

0.44 (0.18)

0.36 (0.13)

p-value

0.1

0.47

0.72

0.68

0.8

0.03

Author Disclosure: S. Sundar: None. B. Sasidharan: None. S. Varghese: None. E. Sam Jeyakumar: None. S. Annamalai: None. R. Singh: None. S. Backianathan: None.

Balu Krishna Sasidharan, MD, MBBS, DNB DMRT

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