Dosimetric comparison between volumetric-modulated arc therapy (VMAT) and helical tomotherapy (HT) in the treatment of bilateral breast cancer (BBC).

Ten patients treated on HT were selected retrospectively. Dose prescription was 50 Gy in 25 fractions to breast/chest wall and supraclavicular fossa (SCF) while tumour bed was simultaneously boosted to 61 Gy in 25 fractions. VMAT plans were made with four mono-isocentric partial arcs. The monitoring unit (MU) and treatment time were used to quantify the treatment efficiency. Target volumes were compared for homogeneity index (HI), conformity index (CI) while organs at risk (OARs) were compared for relevant dose volumes and integral doses (IDs).

For targets, no significant difference is observed between VMAT and HT in CI but VMAT could give better HI. The mean lung dose, V20 and V5 is 10·6 Gy versus 8·4 Gy (p-value 0·03), 12% versus 11·5% (p-value 0·5) and 78·1% versus 43·4% (p-value 0·005), respectively. The mean heart dose, V30 and V5 is 4·9 Gy versus 4·7 Gy (p-value 0·88), 0·5% versus 1·5% (p-value 0·18) and 26·2% versus 22·8% (p-value 0·4). Integral dose (ID) for the whole body and heart are comparable: 289 Gy kg versus 299 Gy kg (p-value 0·24) and 2·9 Gy kg versus 2·8 Gy kg (p-value 0·80). ID for lungs was significantly higher with VMAT: 7·9 Gy kg versus 6·3 Gy kg (p-value 0·03). There is a 53% reduction in treatment time and 78% in MU with VMAT against HT.

VMAT can generate clinically acceptable plans comparable to HT for BBC. HT shows better control over low dose spillage in lungs compared to VMAT thereby increasing ID to lungs. VMAT shows better homogeneity and efficient treatment delivery than HT.

Breast cancer is the most common cancer among females worldwide. Increasing breast cancer incidence rates, improved diagnosis and management modalities and growing life expectancy have resulted in increasing numbers of women at risk of developing contralateral primary breast cancer. Bilateral breast cancer can occur synchronously or metachronously.

This study reports three cases of bilateral breast cancer patients treated at our oncology department between March 2018 and March 2019. The features of presentation, investigation, diagnosis and follow-up care are the highlights of this study.

Bilateral breast cancer was noted in three patients among the study population in the age group of 35 –55 years. Two of these patients had metachronous bilateral breast cancer, and one patient developed cancer in the second breast during the course of management. The second breast cancers differed histologically from primary breast cancer.

Poor awareness on breast cancer care and the lack of national screening guidelines and programmes, and poor infrastructure, all contribute to late presentation and difficult breast cancer management. Proper history, clinical examination and imaging of opposite breast should be done to ensure adequate and timely management of bilateral breast cancer.