A. Lukez1, B. Egleston2, P. L. Lee1, and J. G. Price3; 1Department of Radiation Oncology, Fox Chase Cancer Center, Philadelphia, PA, 2Department of Biostatistics and Bioinformatics, Fox Chase Cancer Center, Philadelphia, PA, 3Fox Chase Cancer Center at Temple University Hospital, Philadelphia, PA
Purpose/Objective(s):This study aims to leveragea national hospital-based cancer registry to examine the evolving trends in radiation therapy (RT) modality with outcomes among medically inoperable endometrial cancer patients treated with varying radiation doses.Materials/
Methods: The analysis included patients in the National Cancer Database (NCDB) with International Federation of Gynecology and Obstetrics stage I–IIIC2 inoperable endometrial cancer treated with radiation, with or without chemotherapy, from 2004 to 2019. Practice patterns compared external beam radiation therapy (EBRT) and brachytherapy (BT) modality and total RT doses, categorized into three groups: EBRT palliative (= 3,000 cGy), EBRT +/- BT definitive low dose (DLD, 4,500 – 6,249 cGy), and EBRT +/- BT definitive high dose (DHD, = 6,250 cGy). Overall survival (OS) was evaluated using the Kaplan-Meier method, and multivariable (MVA) Cox proportional hazard modeling assessed variables associated with OS. Results: The NCDB dataset comprised 1,755 patients (palliative: 541, DLD: 530, DHD: 684). The palliative cohort was older (median age [y] palliative: 76, DLD: 70, DHD: 69) and presented more frequently with advanced stage (p < 0.001) and higher-grade tumors (p < 0.001). The prescription of a palliative dose regimen decreased over time (p < 0.001), notably between 2014 (palliative EBRT cases: 58 [41%], definitive EBRT + HDR: 84 [59%]) and 2019 (palliative EBRT cases: 11 [10%], definitive EBRT + HDR: 96 [90%]).Predictors of palliative dose, compared to DHD, included stage III disease (OR 2.69, p = 0.029), Black race (OR 1.66, p</span> = 0.008), N2 disease (OR 3.36, p = 0.029), poorly differentiated (PD) tumors (OR 1.64, p = 0.02), and undifferentiated (UD) tumors (OR 3.41, p = 0.002). Chemotherapy administration was associated with decreased utilization of a palliative dose regimen (OR 0.040, p < 0.001). Predictors of DLD, compared to DHD, included stage III disease (OR 3.29, p = 0.011), Hispanic origin (OR 1.95, p = 0.021), and Black race (OR 1.56, p = 0.023).MVA exhibited a lower mortality rate for definitive dose with external beam boost (HR 0.54, p < 0.001) or BT boost (HR 0.45, p < 0.001) compared to palliative dose. There was no significant difference in mortality between DLD (HR 1.02, p = 0.76) versus DHD. Receipt of chemotherapy was associated with reduced mortality (HR 0.58, p < 0.001). Worse OS was associated with increasing age (HR 1.03, p < 0.001), increasing clinical T stage (T1 vs T2 HR 1.52, p = 0.038), lymph node involvement (N0 vs N1 HR 1.68, p < 0.001; N0 vs. N2 HR 2.05, p < 0.001), and worse grade (well differentiated (WD) vs. moderately differentiated HR 1.29, p = 0.007; WD vs PD HR 1.70, p</span> < 0.001; WD vs UD HR 2.58, p < 0.001). Conclusion: A definitiveRT dose for medically inoperable endometrial cancer is associated with improved OS. Over time, a combined definitive approach involving EBRT and BT has increased relative to palliative EBRT.
