Dosimetric study of SIB-IMRT versus SIB-3DCRT for breast cancer with breath-hold gated technique

Suresh Moorthy,Hamdi Sakr,Narayana Murthy,Shaima Al-Janahi,Jacob Samuel,Shubber Hasan

doi:10.14319/ijcto.0101.10

Abstract

Background and Purpose: 3-dimensional conformal therapy (3DCRT) is widely employed radiation therapy technique for breast cancer, but there is still need to minimize the doses to organ at risk (OAR) using 3DCRT. A few clinical studies have discussed using intensity modulated radiation therapy (IMRT) to address this shortfall. Simultaneous integrated boost (SIB) has been used in head and neck and prostate cancer, and there is a growing interest in using SIB for breast cancer too. This study aimed to compare SIB-IMRT versus SIB-3DCRT for breast cancer patients. Materials and Methods: SIB-3DCRT treatment plans were created for 36 consecutive patients. Dose was prescribed as 45 Gy in 25 fractions to the planning target volume (PTV)-1 and 60 Gy in 25 fractions to PTV-2. Treatment plans were normalized to 95% of PTV volume receiving 95% of the prescription dose. The conformity index (CI), homogeneity index (HI), lung dose, heart dose, left anterior descending artery(LAD) dose, and low dose volume and integral dose of normal healthy tissue were recorded and analyzed. Results: With the use of IMRT technique, there was an improvement in CI (0.14) when compared to CI of 3DCRT (0.18; p = 0.01). However, there was no significant difference in the HI (p = 0.45). On average, the V 20Gy of ipsilateral lung was 37.9 % for 3DCRT and 22.4 % (p < 0.01) for IMRT, whereas the V 20Gy of total lung (ipsilateral + contralateral) was 21.8% for 3DCRT and 12.14 (p < 0.01) for IMRT. Similarly, average V 40Gy of heart was 7.5 % for 3DCRT and 2.13 % (p = 0.01) for IMRT. The LAD maximum dose to left side breast patients, on average, was 39.5 Gy for 3DCRT and 29.17 Gy (p = 0.03) for IMRT. The average number of monitor units was about 180 for 3DCRT and 1441 (p < 0.01) for IMRT. Conclusion: IMRT for breast cancer treatment is feasible. In comparison to 3DCRT, IMRT can reduce the maximum dose to the target volume, and dose to the OAR. However, 3DCRT technique is superior in terms of low dose volume, integral dose, and treatment time. With the use of breath-hold gated technique in IMRT, it can further improve the target coverage and reduction of doses to the heart, lung, and LAD. SIB technique could reduce the overall treatment duration by about one week. ---------------------------------- Cite this article as: Moorthy S, Sakr H, Hasan S, Samuel J, Al-Janahi S, Murthy N. Dosimetric study of SIB-IMRT versus SIB-3DCRT for breast cancer with breath-hold gated technique. Int J Cancer Ther Oncol 2013; 1 (1):010110. DOI : http://dx.doi.org/10.14319/ijcto.0101.10

Highlights

Breast cancer is the most common malignancy in women
An introduction of linear accelerators has made 3-dimensional conformal radiotherapy (3DCRT) as a standard treatment technique, which can re-duce the doses to the lung, heart, and other critical structure doses in the breast cancer treatment
It is possible to obtain concave and convex shape dose distributions with intensity modulated radiation therapy (IMRT), and it has the ability to conform radiation dose to irregular target volumes sparing the underlying critical structures resulting in better tumor control probability (TCP) and reduced normal tissue complication probability (NTCP)

Summary

Introduction

Breast cancer is the most common malignancy in women. Radiotherapy is an integral part of breast cancer management either in breast conservation surgery (BCS) or in postCite this article as: Moorthy S, Sakr H, Hasan S, Samuel J, Al-Janahi S, Murthy N. Using 3DCRT, it is not always possible to achieve adequate normal tissue sparing, especially when treating left side chest wall patients. This is mainly due to overlying concave shape of the target, which can result more doses to adjacent structures such as heart and lung. It is possible to obtain concave and convex shape dose distributions with IMRT, and it has the ability to conform radiation dose to irregular target volumes sparing the underlying critical structures resulting in better tumor control probability (TCP) and reduced normal tissue complication probability (NTCP). The main purpose of this study was to further evaluate normal tissue sparing and dosimetric analysis of simultaneous integrated boost (SIB)-3DCRT and SIB-IMRT in breast patients, with focus on breath-hold gated technique

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