Organ at risk doses in hypo fractionated three dimensional conformal radiotherapy in carcinoma breast following breast conservation surgery

Abstract

Author(s): Joneetha Jones, Vinin NV, Geetha Muttath, Nabeel Yahiya, Shoaib Nawaz, Arun P Narendran, Ayisha Reja

Breast cancer is the most frequently diagnosed cancer globally and is the leading cause of cancer-related death in women. Adjuvant radiation forms an integral component in the treatment of patients following breast conservation surgery. Techniques for radiation has evolved from conventional 2D dimensional techniques to 3D conformal radiotherapy and Intensity modulated radiotherapy. The survival of breast cancer has improved because of advances in treatment and hence toxicities are of major concern as far as quality of life is concerned. In breast radiotherapy, organ at risk include lungs, heart, contra lateral breast and spinal cord. When compared to conventional 2D dimensional RT techniques 3DCRT can improve dose homogeneity and can better reduce the organ at risk doses. Hypo fractionated RT has gained significant popularity as adjuvant treatment post breast conserving surgery, based on the results of several randomized trials. This study aims to find out the organ at risk doses and dosimetric parameters in post breast conservation surgery treated with a hypo fractionated schedule at our centre. Materials and Methods: Dosimetric details of 32 patients treated with 3DCRT during the period from 01/01/2016 to 01/01/2018 were retrospectively analysed. All patients received EBRT dose of 40 Gy in 15 fractions followed by photon boost of 10 Gy in 5 fractions. Dose volume Histograms were analysed from the Eclipse treatment planning system and necessary data was collected. Results: A total of 32 patients were included. 17 patients had right sided tumours whereas 15 had left sided lesions. All patients were treated with 2 tangential fields, medial and lateral tangents. In addition 17 patients had radiation to supra clavicular fossa and 5 patients received radiation to axilla in addition. The mean ipsilateral lung dose in our study was found to be 11.05 Gy (Standard Deviation 2.55). The mean v20 of ipsilateral lung was found to be 21.27% (standard deviation 6.38). The mean contra lateral lung dose was 0.549 Gy (standard deviation 0.458). The mean heart dose was 6.51 Gy (SD 3.23) for left sided tumords.15 patients had right sided tumours. The mean heart dose was 1.50Gy (SD 1.69) %. In our study the mean V25 was 7.2% for heart for left sided tumours which was within acceptable limits. The mean Dmax to spinal cord achieved was 23.5 Gy (SD 16.53). The mean homogeneity index was 1.17 (sd-0.05). The mean conformity index was 0.89(SD-0.03). Conclusion: 3 Dimensional conformal radiotherapy technique can effectively reduce the organ at risk doses in breast radiotherapy. Also it can yield better dose distribution and better dose homogeneity.

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