Effect of Bolus Frequency and its Thickness in Post- mastectomy Three-dimensional Conformal Radiotherapy on Skin Dose for Superposition Algorithm

Document Type: Original Paper

Authors

1 ESMaR, Faculty of Science, Mohammed V University in Rabat, Rabat, Morocco

2 LPMR, Faculty of Science, University Mohamed 1st, Oujda, Morocco

Abstract

Introduction: Postoperative radiotherapy is the treatment of choice to lower loco-regional recurrence rate and enhance the survival of high-risk breast cancer patients undergoing mastectomy. The post-mastectomy radiation therapy uses bolus to improve the coverage close to the skin, but it needs to be removed in case of the severe skin toxicity. This study investigates the effect of bolus parameters (frequency and thickness) for superposition algorithm (SUP) on skin dose in post-mastectomy three-dimensional conformal radiotherapy (3D-CRT).
Materials and methods: Twenty-two patients have been considered in this study. First, all the plans have been calculated without using bolus. Then, the plans have been recalculated using different bolus frequencies (5, 10, 15, 20 and 25) and thicknesses (0.5 and 1 cm). To evaluate the dose delivered to the skin, a 2 mm thick skin was profiled and a statistical analysis was performed by studying the dosimetric parameters (minimum, mean and maximum) of chest-wall skin.
Results: The superficial part coverage of planning tumor volume (PTV) was better using bolus. In the case of skin, for each bolus frequency, no statistical difference was observed when comparing skin dosimetric parameters 0.5 and 1 cm bolus thicknesses. The bolus frequency increase demonstrates a noticeable difference in the minimum and the mean skin doses (p≤0.05), while the maximum shows no significant difference with respect to bolus frequency (p˃0.05).
Conclusion: The results indicated that the bolus use has a significant effect on the chest-wall skin dosimetric parameters depending on bolus frequency not bolus thickness. However, these later parameters improved the superficial coverage of PTV. Therefore, the choice of bolus frequency and bolus thickness could influence, in certain cases, the clinical decisions.

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Articles in Press, Accepted Manuscript
Available Online from 04 December 2018
  • Receive Date: 18 September 2018
  • Revise Date: 17 November 2018
  • Accept Date: 04 December 2018