Abstract
Purpose: The study was performed comparing dosimetric characteristics of volumetric modulated arc therapy (VMAT) and field-in-field (FiF) techniques on a patient with synchronous bilateral breast carcinoma. Methods: The patients with bilateral breast cancer treatment were included in this study. A total dose of 40.05 Gy in 15 fractions was prescribed to the Planning Target Volume (PTV) of the whole bilateral breast cancer with the supraclavicular and infraclavicular nodes, with a complementary boost of 10 Gy in 4 fractions to the surgical bed (PTVboost). For both radiotherapy techniques, several VxGy parameters were analyzed for the PTVs, together with the Conformity index (CI), the Homogeneity index (HI) and the critical organs at risk (OARs), lungs and heart. Results: The patient was treated by the VMAT technique and the daily treatment time was less than 20 minutes with daily CBCT imaging. In the VMAT plan, the PTV 95% dose covered 38.89 ± 0.81 Gy, compared to 37.26 ± 1.02 Gy in the FiF technique. The VMAT plan improved the dose homogeneity index and lower dose in lung towards high dose region. Conclusion: The study demonstrates the viability of the VMAT technique in the treatment of bilateral breast cancer. The introduced single isocentric VMAT technique is fast to deliver and it increases the dose homogeneity of the target volume with some limitations. The treatment was well tolerated, without interruption of the treatment courses caused by treatment-related toxicities.
Highlights
Breast cancer is the most common cancer in women, constituting 24.2% according to GLOBOCAN 2018 [1]
We compared the two treatment plans to determine which one would offer the best coverage of our target areas, while at the same time minimizing the dose to organs at risk (OARs)
For the 15 volumetric modulated arc therapy (VMAT) sessions, a single daily cone-beam CT (CBCT) imaging was performed for patient setup
Summary
Breast cancer is the most common cancer in women, constituting 24.2% according to GLOBOCAN 2018 [1]. Synchronous bilateral breast cancer (BBC) is defined as two or more malignant tumors occurring simultaneously in both breasts. Synchronous bilateral breast cancer is an uncommon finding in women, presenting multiple breast lumps with an estimated incidence of 2.1% [2]. Bilateral breast cancers are classified depending on the time of occurrence into synchronous (detected simultaneously or within a 6 months gap) or metachronous [3] (detected in an interval longer than 6 months). Risk factors are familial breast cancer, young age, lobular invasive carcinoma, multicentricity, BRCA 1 & 2 gene mutations and radiation exposure [4]. Adjuvant radiotherapy for breast cancer is classically given using medial and lateral tangential fields
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