Abstract OT3-15-03: The ARETTA Trial Experience: Radiotherapy Quality Assurance in an International Breast Cancer Trial

Abstract Background The ARETTA trial is a Phase II feasibility study that tests the efficacy of Taxotere + Herceptin subcutaneous (SC) X 4 cycles in the neoadjuvant setting and one year of Herceptin SC as adjuvant therapy for HER2 positive breast cancer among Nigerian women. This study is being used to test an emerging platform for future biomarker based multi-institutional oncology clinical trials in Nigeria and across Sub-Saharan Africa. Radiotherapy is an integral part of multimodality breast cancer care. However, there are fewer than ten radiotherapy centers in Nigeria and limited experience in delivering radiotherapy within the context of a clinical trial. We describe the processes incorporated within the ARETTA trial to ensure protocol compliance and radiotherapy quality and to enhance patient safety. Methods To centralize treatment, patients from the five participating sites throughout Nigeria were all referred to the Department of Radiotherapy, Lagos University Teaching Hospital (LUTH) to receive radiotherapy. A Radiation Therapy Quality Assurance (RTQA) program was also implemented to ensure protocol compliance and enhance patient safety. This consisted of preparatory educational lectures on breast radiotherapy contours, treatment planning and plan assessment. Subsequently, pre-treatment review of contours was conducted by two radiation oncologists with expertise in breast cancer. Feedback on contours was provided via Zoom conference and email correspondence and weekly ARETTA trial meetings were used to track patient progress and adverse effects. An audit was conducted after treating 24 patients (half of the target enrollment). Patients were registered after lumpectomy or mastectomy and treated as follows: Hypofractionated radiation to the breast alone, breast and regional nodes, chest wall alone, or chest wall and regional nodes. The regional nodes will consist of the supraclavicular fossa, axilla and internal mammary nodal basin. The prescribed dose is 42.56 Gy in 16 daily 2.66 Gy fractions. Boost dose for the lumpectomy cavity or close/positive margins post-mastectomy is 10 Gy in 5 fractions of 2 Gy for cumulative total doses of 52.56 Gy. If there is suspected gross disease, these regions are treated with a boost dose of 18 Gy in 9 fractions of 2 Gy for a total dose of 60.56 Gy in 25 fractions. Treatment is given 5 days a week for 3-4 weeks. In the case of a departmental holiday, RT may be given 4 days a week. In case of medical illness or RT side effect(s), treatment breaks are allowed as needed per standard practice. Results The average surgery to RT start interval was 82 days (range 73 – 161 days). The average duration of RT was 23.1 days (range 18-35 days) and all patients who began RT completed their course of treatment. Radiation oncologists were able to independently and accurately contour targets after attending preparatory lectures and intensive review of the first ten patients. While breast and chestwall target coverage met protocol stipulations, deviations of mean heart dose and internal mammary chain target goals were noted. No Grade 3 or 4 side effects were noted. Conclusion The implementation of RTQA procedures enhanced protocol compliance. Additional educational efforts focused on dosimetric planning and plan assessment are needed to enhance adherence to organ constraints and target goals as stipulated in the protocol. Citation Format: Onyinye Balogun, Anthonia Sowunmi, Atara Ntekim, Adewumi Alabi, Olufunmilayo I. Olopade. The ARETTA Trial Experience: Radiotherapy Quality Assurance in an International Breast Cancer Trial [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr OT3-15-03.