Main Session
Sep 29
PQA 06 - Genitourinary Cancer, Gynecological Cancer, and Health Care Access and Engagement

3738 - Improving Outcomes in Bulky, Eccentric Locally Advanced Cervical Cancer: A Prospective Study of VMAT-Based Simultaneous Integrated Boost Radiotherapy for Lateral Para-cervical High-Tumor-Burden Region

02:15pm - 03:30pm ET
Poster Hall - Exhibit Hall A
Screen: 23
POSTER

Presenter(s)

Yuyan Gao, MD, PhD Headshot
Yuyan Gao, MD, PhD - Beijing Luhe Hospital, Beijing, beijing

Y. Gao1, X. Nan1, X. Liu1, X. Zheng2, Q. Liu3, S. Zhong2, and C. Fan2; 1Beijing Luhe Hospital, Beijing, China, 2Beijing Luhe Hospital, beijing, China, 3Department of Radiation Oncology, Beijing Luhe Hospital, Beijing, China

Purpose/Objective(s):

To evaluate the clinical efficacy and safety of a radiotherapy regimen combining volumetric modulated arc therapy (VMAT)-based simultaneous integrated boost (SIB) to the lateral para-cervical high-tumor-burden region during standard pelvic external beam radiotherapy (EBRT), followed by conventional intracavitary brachytherapy (ICBT), for patients with bulky, eccentric locally advanced cervical cancer (LACC).

Materials/Methods:

This prospective study enrolled 33 patients with pathologically confirmed LACC (FIGO IIA2-IVA) presenting with bulky tumors (maximal diameter =5 cm or volume =40 cm3), asymmetric lateral parametrial extension, and midline uterine deviation >1 cm. Between September 2021 and December 2024, all patients received EBRT with VMAT-based SIB followed by ICBT. The EBRT prescription was: 54-56.6 Gy in 25-27 fractions (2.1-2.2 Gy/fraction) to the Cervical lateral High-Tumor-Burden Region (GTV-H); 60-62.1 Gy in 25-27 fractions (2.3-2.4 Gy/fraction) to involved lymph nodes (PGTVnd); and 48.6-50 Gy in 25-27 fractions (1.8-2 Gy/fraction) to the planning target volume (PTV). ICBT delivered 5 fractions with a prescription dose of 6 Gy/fraction to the high-risk clinical target volume (HR-CTV) and 5 Gy/fraction to the intermediate-risk CTV (IR-CTV). Organs at risk included the rectum, sigmoid colon, bladder, small bowel, and femoral heads. All patients received concurrent weekly cisplatin (40 mg/m²).

Results: The initial mean tumor volume was 78.2 ± 56.7 cm³, which significantly reduced to 7.3 ± 11.5 cm³ at the time of brachytherapy. All patients completed the prescribed radiotherapy. For the high-risk clinical target volume (HR-CTV), the mean D90 was 90.89 ± 2.94 Gy, with an equivalent dose in 2 Gy fractions (EQD2) of 98.15 ± 5.33 Gy. Key organ-at-risk dose parameters were: bladder – Dmax 80.36 ± 5.4 Gy, D2cc 70.08 ± 4.9 Gy, V30 48.51 ± 3.89%; rectum – Dmax 77.14 ± 3.81 Gy, D2cc 65.71 ± 3.07 Gy; sigmoid colon – Dmax 71.43 ± 7.68 Gy, D2cc 59.96 ± 6.01 Gy; small bowel – Dmax 71.63 ± 8.36 Gy, D2cc 59.56 ± 5.53 Gy; left femoral head – Dmax 37.45 ± 3.57 Gy, V30 2.27 ± 4.16%; right femoral head – Dmax 37.04 ± 3.53 Gy, V30 1.64 ± 2.13%.Median follow-up was 34.45 months (8.26-54.96 months).Three-year overall survival rate, progression-free survival rate, and local control rate were 96.96%, 87.88%, and 100%, respectively.Grade 1-2 hematological toxicity occurred in 39.39% ,Grade 3-4 hematological toxicity occurred in 60.6%. Grade 1-2 rectal and genitourinary toxicities were observed in 21.21% and 9.09% , with no Grade =3 events.

Conclusion:

VMAT-based SIB radiotherapy targeting the cervical high-tumor-burden region during pelvic EBRT combined with conventional ICBT provides excellent local control and survival outcomes with an acceptable toxicity profile for patients with bulky, eccentric LACC.