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

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).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.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%.The POLO approach is technically feasible and capable to achieve a significant reduction of radiation dose delivered to the previous treated IOERT area.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.