Dosimetric Evaluation of Oesophagus in Hypofractionated Supraclavicular Nodal Irradiation in Breast Cancer - A Retrospective Observational Study in a Tertiary Care Cancer Centre in Alappuzha, Kerala

BACKGROUND Acute esophagitis (AE) is a common toxicity seen in patients undergoing radiotherapy (RT) for breast cancer, which can affect their quality of life. Thus, majority of our patients receiving hypo fractionated dose of 40 Gy in 15 fractions were having AE. We conducted this study to evaluate the dosimetric parameters of oesophagus and correlate with published literature. METHODS Treatment plans of 80 post mastectomy patients who underwent radiotherapy for carcinoma of breast (Ca breast) with a dose of 40 Gy in 15 fractions to the chest wall along with supra clavicular fossa (SCF) were selected. Out of these, 44 patients (22 each in right and left side) were simulated in neck straight position and 36 in neck tilted position (18 each in right and left side). The oesophageal volume was contoured in already executed plans from the inferior border of cricoid cartilage to the inferior border of the SCF planning target volume (PTV). No plan modification was done after contouring the oesophagus. Dosimetric parameters like the maximum dose (Dmax) and mean dose (Dmean) to oesophagus, volume of oesophagus receiving ≥ 5 Gy (V5), ≥ 10 Gy (V10), ≥ 15 Gy (V15), ≥ 20 Gy (V20), ≥ 25 Gy (V25), ≥ 30 Gy (V30) were derived from dose volume histogram (DVH) data and analysed. RESULTS Dmean in straight neck group irrespective of side was 18.57 (± 7.30) Gy and in tilted neck 22.94 (± 9.53,) Gy, P = 0.023. Subgroup analysis shows Dmean was significantly high in patients with left sided disease than those with right sided disease (24.10 vs. 13.03, P = 0.00) in the straight neck cases. In the neck tilted group there was a nonsignificant increase in Dmean in left sided cases (25.36 vs. 20.53, P = 0.13). CONCLUSIONS Evaluation of oesophageal dosimetric parameters in hypofractionated dose showed that DmeanEQD2 was within the values of published studies in conventional fractionation. KEYWORDS Oesophageal Dosimetric Parameters, Breast Cancer