Does gastric volume impact lung’s exposure in loco-regional left-sided breast cancer radiotherapy?
PO-2338
Abstract
Does gastric volume impact lung’s exposure in loco-regional left-sided breast cancer radiotherapy?
Authors: Zeineb Naimi1, Meriem El Bessi1, Meriem Bohli1, Raouia Ben Amor1, Awatef Hamdoun1, Rihab Haddad1, Lotfi Kochbati1
1Abderrahmen Mami Hospital, Radiation Oncology Department, Ariana, Tunisia
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Purpose or Objective
The aim of this study was to assess the impact of gastric volume on doses delivered to the homolateral lung in left-sided loco-regional breast cancer irradiation.
Material and Methods
We prospectively evaluated fifty women referred for adjuvant left-sided breast cancer loco-regional radiotherapy. All patients underwent 3D-conformal hypofractionated radiotherapy (40 Gy/15 fractions ± boost of 13.35 Gy), by two breast tangential fields plus a supraclavicular field, using a mono-isocentric technique. For each patient, the stomach was contoured and the gastric volume was assessed. Dose-volume histograms were generated. Statistical associations between gastric volume and left lung’s dosimetric parameters (mean dose, V20Gy, V30Gy) were analysed.
Results
Mean age was 47.5 years. Thirty-eight patients (77,6%) had T1-2 tumors. Breast conservative surgery was performed in 38% of cases. All patients received chemotherapy, neoadjuvant in 18% of the cases. Forty-three patients (86%) underwent adjuvant endocrine therapy and 32% received trastuzumab. All patients were planned for loco-regional radiotherapy. An additional boost was delivered in 42% of cases.
Mean gastric volume was 194,38 (78-573) cc. No statistically significant correlation was found between gastric volume and V20 Gy, V30 Gy and the mean lung dose with Pearson correlation coefficient of - 0,6 (p=0,66), - 0,7 (p=0,6) and -0,6 (p=0,67), respectively. The contribution of supraclavicular field to lung’s doses et exposed volumes was on average of 37%, 32% and 39% respectively for the mean lung dose, V20 Gy and V30 Gy. Although not statistically significant, gastric volume tended to correlate with V30 Gy to the lung, when considering only the supraclavicular field dose contribution (p=0.02). Neither the primary (CTVp) nor nodal clinical target volumes (CTVn) volumes were correlated to lung’s doses.
Conclusion
This study showed that gastric volume did not impact doses delivered to the left lung, suggesting that pre-planning/treatment fast protocols are not needed in left-sided breast cancer radiotherapy.