Sep 29

QP 29 - Response Assessment and Risk Stratification in Gynecologic Cancers: Biomarkers, Imaging, and Outcomes

1173 - Morbidity of Pelvic Recurrence in Stage III Uterine Serous Carcinoma

05:40pm - 05:45pm ET

Room 257

Presenter(s)

Mary-Kate Lawlor, MD - Yale New Haven Health, New Haven, CT

M. K. K. Lawlor¹, V. Lee², S. E. Gueble³, and S. Damast⁴; ¹Yale New Haven Health, New Haven, CT, ²Department of Therapeutic Radiology, Yale School of Medicine, New Haven, CT, ³Yale School of Medicine, New Haven, CT, ⁴Department of Therapeutic Radiology, Yale University School of Medicine, New Haven, CT

Purpose/Objective(s):

Due to the poor prognosis of stage III p53abn/uterine serous carcinoma (USC), carboplatin/paclitaxel (C/T) is the mainstay of adjuvant therapy. The role of external beam radiotherapy (EBRT) remains controversial, and some patients receive vaginal brachytherapy (VBT) as an alternative; however, high rates of locoregional recurrence in the absence of EBRT can be morbid. We hypothesize that by delivering EBRT sequentially, following 6 cycles of C/T, there will be improved regional disease control without a detriment to distant control, and overall improved oncologic outcomes.

Materials/Methods:

This IRB-approved, retrospective, single institution analysis included all surgically staged, stage III USC patients treated from 1/2003 through 10/2025 with radiation (EBRT and/or VBT) sequentially with C/T. Primary outcomes were recurrence-free survival (RFS), overall survival (OS), and morbidity of treatment and recurrence. Chi-square and Kaplan- Meier methods were used for analyses. CTCAE v5 was used to grade toxicities.

Results:

Among 81 patients that met criteria, 50 patients received VBT and 31 received EBRT (+/- VBT). Other than higher median age in the VBT vs EBRT group (73 vs 65, p < 0.001), the two groups (VBT vs EBRT) had similar distributions of race, body mass index, nodal involvement (54% vs 71%), pure USC histology (70% vs 74% ), molecular profile (100% p53abn, 20% HER-2+), and completion of all 6 cycles of C/T (88% vs 94%).

The median follow-up was 45 months (41 vs 49 in the VBT vs EBRT groups). There were no differences in the 4-year RFS (44% vs 49%, p = 0.362) or distant metastasis free survival (77% vs 66%, p = 0.549). The 4-year OS, pelvic RFS and pelvic/para-aortic RFS were all worse in the VBT vs EBRT group (55% vs 87%, p = 0.02; 65% vs 95%, p = 0.01; and 53% vs 74%, p = 0.04, respectively). There were no = grade 3 toxicities related to EBRT, but among the 27 patients who suffered pelvic or para-aortic recurrences, = grade 3 toxicities related to disease were present in 44% (n=12) and included hospitalization for acute kidney injury, urosepsis, nephrostomy, colostomy, inferior vena cava filter, lymphedema, palliative debulking surgery, and inpatient pain control. In addition, survival among patients who suffered pelvic or para-aortic recurrences was significantly worse compared with those who did not (OS at 4 years 36% vs 83%, p < 0.001).

Conclusion:

Pelvic and regional nodal recurrences were prevalent, morbid, and generally not salvageable among surgically staged, stage III p53abn/USC patients that did not receive EBRT. EBRT was not associated with reduced ability to complete 6 cycles of C/T or increased risk of distant metastases. EBRT did not cause = G3 toxicity. While EBRT was not associated with improved RFS, it was associated with improved OS, possibly due to prevention of morbid and fatal regional nodal recurrences, though further prospective investigation is needed.