3759 - Association Between Organ Puncture and Acute Toxicity Following CT-Guided Interstitial HDR Brachytherapy for Gynecologic Malignancies: A Retrospective Cohort Study
Presenter(s)
S. Amin1, J. M. Grant2, L. A. Garrett3,4, and J. W. Jang1,4; 1Department of Radiation Oncology, Beth Israel Deaconess Medical Center, Boston, MA, 2Beth Israel Deaconess Medical Center, Department of Obstetrics and Gynecology, Boston, MA, 3Beth Israel Deaconess Medical Center, Department of Obstetrics and Gynecology, Division of Gynecologic Oncology, Boston, MA, 4Harvard Medical School, Boston, MA
Purpose/Objective(s): Interstitial brachytherapy (ISBT) is often preferred to intracavitary brachytherapy for bulky cervical or vaginal cancers and vaginal recurrences of endometrial cancer. During interstitial needle placement, non-gynecologic organs may be intentionally or unintentionally punctured, which can be identified radiographically, raising concern for complications such as peritonitis, sepsis, and bleeding, although the clinical significance remains uncertain. We evaluated whether radiographic organ puncture during CT-guided interstitial HDR brachytherapy is associated with increased acute toxicity within the first 3 months of finishing treatment.
Materials/Methods: We retrospectively reviewed patients treated with CT-guided ISBT from 2014–2025. CT simulation images were assessed for radiographic organ puncture (OP) versus no puncture (NOP). Acute toxicities were graded per CTCAE v6.0 and analyzed at the patient level by organ system. Baseline, treatment, dosimetric variables, and toxicity distributions were compared using Wilcoxon rank-sum and Fisher’s exact tests.
Results: We identified 79 patients treated with ISBT, with a median follow-up of 2.7 months. Most patients had cervical (39%), endometrial (31%), vaginal (25%), vulvar (4%) or other subtypes (1%) cancer, with 32% having recurrent disease. Organ puncture was identified retrospectively in 40 patients (51%), involving the sigmoid (60%), rectum (33%), bladder (20%), and small bowel (18%). Compared with NOP, the OP cohort had lower body mass index (BMI, 28 vs 31 kg/m², p=0.01), more needles inserted (19 vs 16, p=0.03), and higher sigmoid D2cc (55.8 vs 52.7 Gy EQD2, p=0.03). Most acute toxicities were Grade 1–2. There were no differences in Grade =3 gastrointestinal or genitourinary toxicities between the OP and NOP groups. In the OP cohort, 10% of patients had a Grade =3 gynecologic toxicity compared to 2.6% in the NOP cohort (p=0.02). No gynecologic Grade 4 events occurred. There were no Grade 5 events, and no Grade =3 events required surgical intervention in any domain. Skin and other toxicities were infrequent and similar between groups.
Conclusion: Organ puncture during CT-guided ISBT was associated with lower BMI, greater needle number, and higher sigmoid dose. However, radiographic organ punctures did not translate into clinically meaningful gastrointestinal or genitourinary morbidity. Although Grade =3 gynecologic toxicity differed statistically, overall high-grade events were infrequent and did not require surgical intervention. Overall, no acute life-threatening complications occurred. These findings support the safety and tolerability of CT-guided interstitial HDR brachytherapy when intracavitary techniques are insufficient.