The POLO (Partially Omitted Lobe) approach to safely treat in-breast recurrence after intraoperative radiotherapy with electrons

Objectives: The aim of this study is to evaluate feasibility of salvage 4-week hypofractionated whole breast radiotherapy (WBRT) in patients with in-breast recurrence after receiving intraoperative radiotherapy with electrons (IOERT) for primary breast cancer (BC). Methods: BC patients who had repeated quadrantectomy underwent modified WBRT with intensity-modulated radiotherapy using Helical Tomotherapy to underdose the IOERT region. This approach, called POLO (Partially Omitted Lobe), excluded the IOERT volume from receiving the full prescription dose. Results: Nine patients were treated with this approach, receiving 45 Gy in 20 fractions. A simultaneous integrated boost of 2.5 Gy in 20 fractions was delivered in 6/9 patients. Dose constraints and planning objectives were reported. No severe toxicity was reported while local control and overall survival were 100%. Conclusion: The POLO approach is technically feasible and capable to achieve a significant reduction of radiation dose delivered to the previous treated IOERT area. Advances in knowledge: The study demonstrates the technical and dosimetric feasibility of conservative salvage whole breast radiotherapy, while sparing the area already treated with IORT, in patients with in-breast recurrence.