Analysing breast dose in female lymphoma patients who received radiotherapy: a retrospective audit

Abstract

Keywords: Lymphoma, Breast cancer, Involved field, Involved node, 3DCRT Introduction: Radiotherapy improves progression-free survival in lymphoma, though it increases the risk of secondary malignancies post-treatment1,2. Second primary breast cancers contribute most to the overall absolute excess risk of secondary malignancy in Hodgkin’s lymphoma patients, with radiotherapy thought to play a major role in carcinogenesis2. However, the relationship between doses received and risk is unclear, and referral to screening programmes is mainly based upon data from out-dated mantle treatments1-5. The aim of this study therefore was to audit breast dose in female patients treatment with conformal radiotherapy approaches for mediastinal-involved lymphoma. Methodology: Patients were selected retrospectively from a locally held database6 of women aged ≤36 who received supradiaphragmatic radiotherapy for lymphoma between 2008-2012. Inclusion criteria: •Mediastinal involvement.•30Gy prescription dose.•AP-PA field arrangement. Exclusion criteria:•Neck only treatments•Plans with breast tissue pre-contoured•Plans with incomplete breast tissue. All breast contours were constructed to RTOG/EORTC guidelines and reviewed by a radiologist7,8. Radiotherapy dose statistics were retrieved from the departmental planning software. Results: 26 patients were analysed. Mean dose to both breasts was 2.3Gy, with some patients with advanced disease receiving at least 4Gy to >80% of a single breast. A mean dose for both breasts of 10.6Gy was observed. Mean Dose to D1% of both breasts combined was 24.5Gy, despite most plans having no breast tissue within the PTV. Discussion and conclusion: Mean dose, V4Gy, V20Gy, and D1% results were predominantly within the maximum and minimum range of mean results in the literature for conformal treatments9-18. Differences in results between patients, stemmed from variability in disease spread and disease location, along with variation in field parameters. Subsequently, advanced stage patients tended to receive significantly higher breast doses, and further audits may wish to examine the implications of this. This audit was limited by a lack of information regarding target volume outlining decision-making and staging. Future audits may also wish to examine the effect of prospective peer review of target volumes on breast dose. Numerical References