University of Texas MD Anderson Cancer Center Houston, TX
K. E. Marqueen1, C. D. Fuller1, Z. Yu1, L. L. Lin2, A. Jhingran1, M. M. Joyner3, T. Cisneros Napravnik1, L. Colbert1, K. H. Lu4, Y. Kim5, A. H. Klopp1, and N. Taku6; 1Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, 2Division of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, 3Department of Breast Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, 4Department of Gynecologic Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, 5Department of Radiation Physics, University of Texas MD Anderson Cancer Center, Houston, TX, 6The University of Texas MD Anderson Cancer Center, Houston, TX
Purpose/Objective(s): Radiation therapy plays a key role in the multimodality management of gynecologic malignancies and involves advanced, conformal treatment delivery techniques that are enhanced with high quality on-board imaging. Magnetic resonance imaging–guided linear accelerators (MR-linacs) integrate real-time MR imaging with radiation treatment delivery to enable targeting MRI targets and daily adaptive treatment. Since MR imaging allows for improved soft tissue resolution over CT, particularly for gynecologic malignancies, the benefits of adaptive MR image guidance can lead to improved tumor coverage and decreased toxicity. Here, we report clinical outcomes for patients with gynecologic cancers treated with definitive radiation therapy using an MR-linac. Materials/
Methods: We identified a retrospective cohort of patients with gynecologic cancers who received at least 5 fractions on the MR-linac as part of a definitive course of therapy. These patients were treated at a tertiary academic cancer center from August 2019 to October 2023. MRL treatment was recommended for patients with gross disease, critical adjacent structures and not candidates for brachytherapy based on disease extent or co-morbidities. Adverse events were assessed using the Common Terminology Criteria for Adverse Events (CTCAE), version 5.0. The Kaplan-Meier method was used to estimate local progression free survival (PFS). Results: We identified 38 patients, with median follow up time of 33.6 months from the initiation of radiation therapy. Median age was 58 years at time of current disease diagnosis. The number of fractions on the MR-linac ranged from 5 to 28, at a median dose of 230 cGy per fraction. Final prescribed MR-linac dose ranged from 1000 to 6160 cGy. Patients were diagnosed with uterine cancer (55.2%), cervical cancer (15.8%), ovarian cancer (7.9%) or other gynecologic cancer (21.1%). 57.9% had recurrent cancers while the remainder were treated definitively for primary disease. Twenty-nine (76.3%) patients received an adapt to position for any fraction, and 12 (31.6%) required an adapt to shape for any fraction. Targets include vaginal cuff alone (12, 31.6%), lymph node (4, 10.5%) vaginal cuff plus a node (4, 10.5%), or other pelvic mass (15, 39.5%). There were no reported treatment-related grade 3+ adverse events. The percentage of patients who had complete response on PET was 55.2%. For all patients, local progression-free survival at 12 and 24 months was 100% and 96.4%, respectively. Conclusion: Use of the MR-linac for definitive treatment of high-risk gynecologic cancers is clinically feasible and effective, with a favorable toxicity profile. Further studies are warranted to confirm these findings in a larger population and identify patients who may benefit most from this technology.
