Dosimetric comparison of four high performance techniques for irradiation of breast cancer patients

The use of IMRT for the treatment of breast cancer has been growing considerably in our institution since 2009. Alternatively, helical tomotherapy (HT) using a field width of 2.5 and 5cm (HT_FW_5), volumetric-modulated arc therapy (VMAT), or proton therapy with pencil-beam scanning (PT-PBS) have also been used to reduce treatment duration or optimize organ-at-risk (OAR) sparing. The purpose of this study was to compare the 4 treatment modalities available at our site.

We studied 10 patients treated for breast cancer with lymph node involvement. The prescribed dose was 51.8Gy to the breast with a simultaneous integrated boost up to 63Gy, and 50.4Gy to lymph nodes in 28 fractions. The CTV was delineated according to ESTRO Guidelines. Dosimetric planning in routine clinical practice was performed using HT_FW_2.5. The approved clinical plan was compared to the 3 other plans. Dosimetric goals for PTV coverage were D95%≥95% and D2%≤107% of the prescribed dose. Mean and maximum doses to OAR were recorded.

HT_FW_5 and VMAT plans ensure equivalent or even better PTV coverage compared to the initial clinically approved plan but at the cost of poorer OAR sparing. PT_PBS plans showed that an excellent PTV coverage can be maintained with significantly lower doses to OAR.

HT_FW_5 and VMAT plans allow a significant reduction of treatment duration and can be a good alternative to HT_FW_2.5 for specific populations. HT_FW_2.5 could be chosen for patients at higher risk of side effects. In addition, PT_PBS should be considered in the near future as it has been shown to have a major potential benefit to lower the risk of side effects with the same level of PTV coverage.