Current best practices and rationalistic perspectives in causation-based prevention, early detection and multidisciplinary treatment of breast and gastric cancer

Gastric & Breast Cancer e-journal
DOI: 10.2122/gbc.2020.0291

Original Article

DOSIMETRIC COMPARISON OF PRONE VERSUS SUPINE HYPOFRACTIONATED PARTIAL BREAST IRRADIATION VIA EXTERNAL BEAM RADIOTHERAPY IN EARLY BREAST CANCER.

Arun T1, V Lokesh1,Uday Krishna A S1, Varathraj C2, Naveen T1, Bindu Joseph1, K P Jagannath1, Tanvir Pasha1, R Vinay Kumar1, Govardhan H B1, Sham Sundar1.

Affiliation:
1 Department of Medical Physics, Kidwai memorial institute of oncology, Bangalore, India.
2 Department of Radiation Oncology, Kidwai memorial institute of oncology, Bangalore, India.

Abstract
Objective
To analyzed the dosimetry of PTV and OARs - heart and lungs in prone versus supine hypofractionated partial breast irradiation.
Patients and Methods
Twenty histologically proven, newly diagnosed early stage carcinoma breast with informed consent were enrolled for the study.
All patient underwent breast conservation surgery followed by Adjuvant RT. A CTV of 1.5cm was generated from the cavity followed by 0.5 mm PTV margins. 3DCRT or IMRT plans were generated in both the positions. Patient was treated in supine position to a dose of 40Gy delivered in 15 fr at 2.66Gy per faction, 1 faction per day over 5 fractions per week. Dose constraints were applied to the OARs namely then ipsilateral lung V30<10%, V20<20%, V30<10% and the heart V20<5%, V10<10% and Dmean<5Gy.
In our study the PTV Dosimetric parameters were assessed using PTV D90, PTV V95 and PTV Dmax. Lung Dosimetric parameters were mean ipsilateral lung V30, V20 and V10 and Heart Dosimetric parameters were V20, V10 and mean heart dose..
Results
Between October 2014 and December 2016, 20 patients were enrolled on the study.
The PTV D90 was 37.91Gy in supine position and 38.03Gy in prone position. The PTV Dmax was 106.22Gy in supine position and 105.87Gy in prone position. The PTV V95 was 91.73% in supine and 93.77% in prone position.
The mean ipsilateral lung V30 was 6.69% in supine and 2.47% in prone position which was statistically significant (p =0.002). The mean ipsilateral lung V20 was 11.05% in supine and 4.87%% in prone position which was statistically significant (p = < 0.001). The mean ipsilateral lung V10 was 17.82% in supine and 7.97% in prone position which was statistically significant (p = < 0.001). The mean ipsilateral lung dose was 6.37Gy in supine position and 3.10Gy in prone position which was statistically significant (p = <0.001).
The Heart V20 was 1.28% in supine position and 1.53% in prone position. The Heart V10 was 3.99% in supine position and 3.19% in prone position. The mean heart dose was 1.86Gy in supine position and 1.48Gy in prone position. None of the parameters were statistically significant.
Conclusions
The DVH parameter for the PTV in prone position were not found to be statistically significant compared to supine position. Prone position in breast irradiation had better dosimetry with ipsilateral lung. Although the cardiac dose was reduced by prone position compared to supine position, DVH parameters V20, V10 and mean heart dose, were not statistically significant.

Key words: Breast, Partial, Hypofractionated, Prone, Supine, PTV, Lung, Heart

(Citation: Gastric & Breast Cancer 2020; 15(1): 8-15)

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last update: 31 January 2020