ESTRO 2023 - Abstract Book

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ESTRO 2023

boost) with concurrent weekly cisplatin (40 mg/m2). Patients received IGBT of 7 Gy × 4 fractions to the High-Risk Clinical Target Volume (HR-CTV). The first fraction was done under MRI guidance and subsequent fractions under CT guidance. Acute toxicity was graded according to the Common Terminology Criteria for Adverse Events, version 5.0. Late toxicity was graded according to RTOG criteria. The primary endpoint was acute toxicity and secondary endpoint was late toxicity and clinical outcome in terms of loco-regional control. Results Patient characteristics are summarized in table 1. Median RT dose was 45Gy (45-55Gy). All patients received concurrent chemotherapy with median number of 5 cycles (4-5). Median overall treatment time was 8 weeks (7-10.5weeks). The median cumulative doses in terms of equivalent dose of 2 Gy (EQD2) of IGBT plus WP-IMRT for D90 HR-CTV,D2cc bladder,D2cc rectum, and D2cc sigmoid colon were 87Gy (81-95.8Gy), 72.95Gy (65.3-83.2Gy), 63.1Gy (57.8-68.8Gy) and 65.6Gy (61.2-75.2Gy), respectively. None of the patient reported grade 3 or 4 acute toxicity. Grade 1 and 2 diarrhea, grade 1 cystitis was reported in 4(16%), 3(12%) patients and 2(8%) patients respectively. Grade 1 anemia, grade 2 anemia, grade 1 dermatitis and grade 2 dermatitis were observed in 3(12%), 2(8%), 3(12%) and 3(12%) patients respectively. At a median follow-up of 24.6 months (18-30 months), late Grade 1 bladder toxicity was observed in 1(4%) patient. No late lower GI and skin toxicity seen till last date of follow-up.Loco-regional control at 6 and 12 months was 96% and 92% respectively.

Patient characteristics Median Age (Range) Median KPS (Range)

Distribution (n=25) 52 years (29-65 years)

90 (80-100) FIGO 2018 Stage IIA:IIB:IIIB:IIIC1 3(12%):10(40%):5(20%):7(28%) Table 1 showing patients characteristics.

Conclusion The combination of IG-IMRT and IGBT yielded favorable dose distribution to tumor volumes with sparing of OARs resulting in excellent outcome in terms of acute and late toxicity profile and loco-regional control.

PO-1430 Re-irradiation with intensity-modulated radiation therapy for pelvic recurrent cervical cancer

H.J. Kang 1 , M. Kimm 1

1 Incheon St. Mary's Hospital, Radiation Oncology, Incheon, Korea Republic of

Purpose or Objective Radiation therapy (RT) is generally used as a primary treatment for cervical cancer because it responds well to radiation. The main recurrence pattern in cervical cancer is intra-pelvic recurrence. This study aimed to investigate the feasibility and safety of re-irradiation using intensity-modulated radiation therapy (IMRT) for patients with cervical cancer who experienced intra-pelvic recurrence. Materials and Methods We retrospectively analyzed 22 patients with recurrent cervical cancer treated with re-irradiation for intra-pelvic recurrence using IMRT between July 2006 and July 2020. The irradiation dose and volume were determined according to the range considered safe considering the tumor , location, and previous irradiation dose. The median re-irradiation dose to the recurrent site was 50 (range: 26–56) Gy. The median cumulative dose from the previous RT and re-irradiation course was 110 (range: 83–148) Gy. Results The median follow-up period was 15 (range: 3–120) months, and the overall response rate was 63.6%. Of the symptomatic patients, 90% experienced symptom relief after treatment. The 1- and 2-year local progression free survival (LPFS) rates were 36.8% and 30.7%, respectively, whereas the 1- and 2-year overall survival (OS) rates were 68.2% and 25.0%, respectively. Multivariate analysis revealed that the interval between irradiations and gross tumor volume (GTV) were significant prognostic factors for LPFS. The response to re-irradiation showed borderline statistical significance for LPFS. The GTV and response to re-irradiation were also independent prognostic factors for OS. Grade 3 late toxicities were observed in 4 (18.2%) of the 22 patients. Recto- or vesico-vaginal fistula occurred in 4 patients. The irradiation dose was associated with fistula formation with borderline significance. Conclusion Re-irradiation using IMRT is a safe and effective treatment strategy for patients with recurrent cervical cancer who previously received RT. The interval between irradiations, tumor , response to re-irradiation, and radiation dose were the main factors affecting efficacy and safety.

PO-1431 A phase I/II study of SBRT boost in patients with cervical cancer who are ineligible for ICBT

K. Ito 1 , Y. Nakajima 1 , H. Ogawa 1 , A. Furusawa 2 , K. Murofushi 1 , S. Kito 1 , N. Kino 2 , T. Yasugi 2 , T. Uno 3 , K. Karasawa 1

1 Tokyo Metropolitan Komagome Hospital, Radiation Oncology, Tokyo, Japan; 2 Tokyo Metropolitan Komagome Hospital, Gynecology, Tokyo, Japan; 3 Chiba University, Radiology, Chiba, Japan

Purpose or Objective