Abstract book - ESTRO meets Asia

S9 ESTRO meets Asia 2018

OC-023 Whole pelvis intensity-modulated radiation therapy with central-shielding for cervical cancer Y. Mukai 1 , A. Sato 2 , H. Inoue 3 , Y. Tayama 2 , K. Matui 2 , T. Fukuda 3 , K. Onuma 3 , T. Inoue 4 , M. Hata 1 , M. Omura 2 1 Yokohama City University Graduate School of Medicine, Radiology, Yokohama, Japan 2 Shonan Kamakura General Hospital, Radiation Oncology, Kamakura, Japan 3 Shonan Kamakura General Hospital, Obstetrics and Gynecology Kamakura, Japan 4 Shonan Kamakura General Hospital, Advanced medical center Yokohama, Japan Purpose or Objective Reduction of the rectal dose is a critical issue for high- dose-rate intra-cavity brachytherapy (HDR-ICBT) of cervical cancer. Because Asian patients have smaller physique compared with Caucasians, it is difficult to keep enough space between HDR-ICBT source and rectal wall. In Japan, the standard external beam radiation therapy (EBRT) is a combination of the whole pelvic radiation therapy (WPRT) and a sequential WPRT with central- shielding (WPRT-CS) using three-dimensional conformal radiation therapy (3D-CRT). The CS was a simple rectangular block placed at the midline to reduce rectal dose before HDR-ICBT. In this study, we applied IMRT with WPRT and WPRT-CS instead of 3D-CRT and evaluate the treatment outcome and toxicities. Material and Methods Thirty consecutive cervical cancer patients treated from 8/2011 to 10/2016 were included in this retrospective analysis. IMRT was performed using TomoTherapy, started with the WPRT followed by WPRT-CS. The total dose of WPRT and WPRT-CS was 50-50.4 Gy/25-28 Fr. The fractions ratio of WPRT and WPRT-CS was determined depending on tumor volume reduction during WPRT. In WPRT-CS, the dose to the rectum and uterus regions where the intensive dose of HDR-ICBT may be distributed was reduced using the IMRT technique (Fig.1) . The dose to the lymph-node regions including pre-sacral region was maintained. The dose to rectum was defined as that to the International Commission on Radiation Units and Measurements (ICRU) reference point.

respectively ( Fig.2 ). Three patients experienced local recurrence and 2 of them developed simultaneous distant metastases. No pelvic lymph-node recurrence was observed. Univariate analysis showed the better OS for those with SCC than those with adenocarcinoma (p = 0.035). Three and 2 patients developed grade 2 (G2) acute gastrointestinal (GI) and genitourinary (GU) toxicities, respectively. Only 2 (6.6%) and no patients developed G2 late GI and GU toxicities, respectively. No ≥ G3 acute or late toxicity was observed.

Conclusion To our knowledge, this is the first report of WPRT and WPRT-CS using IMRT followed by HDR-ICBT for cervical cancer. This combination therapy resulted in excellent outcomes and tolerance rates. OC-024 ct DNA as screening and predictive marker in cervical cancer patients receiving radiotherapy J. Yang 1 , M. Fan 1 , J. Wang 1 , J. Wang 1 , M. Chen 1 , L. Pan 1 , L. Sun 1 1 Sichuan Cancer Hospital, Radiation Onocology, Chengdu, China Purpose or Objective There are no established genomic biomarkers to detect the sub-clinical or micro-residual tumor and predict therapeutic effect of cervical carcinoma. Circulating tumor DNA (ctDNA) is a promising 'liquid biopsy” approach to help us evaluate patient’s genomic background and tumor burdens. In this study we are aiming to use ctDNA to detect residual tumor and therapeutic effect in cervical carcioma. Material and Methods We performed deep targeted sequencing with a 422-gene panel in baseline ctDNA and pathology specimens from 10 radiotherapy-naive cervical cancer patients who received definitive radiation or post-surgery radiation. 8ml serum was collected before treatment for ctDNA detecting and FFPE blocks were collected and tested to provide baseline genomic information. Tumor mutation burdens (TMB) were reported as well. Genomic alterations in ctDNA were examined before and after radiotherapy. Results Table 1 showed the characteristics of patients and ctDNA datas at different checkpoint. ctDNA was detected in 4 of 4 (100.0%) patients receiving definitive radiotherapy at baseline, and the median TMB in ctDNA was 4.4(2.2 to

Results The median age was 64 (range, 38-91) years. Twenty–five had squamous cell carcinoma (SCC) and the other 5 had adenocarcinoma. Tumor stages (FIGO) were distributed as follows: IB: 6, IIA: 2, IIB: 3, IIIA: 1, IIIB: 7, IVA: 1. The median dose of WP and WPRT-CS was 36 (range, 20-41.4) Gy and 14.4 (range, 9-28) Gy, respectively. Median HDR - ICBT dose/fractions to point A was 25 Gy/5 Fr (range, 15- 30 Gy/3-5 Fr). Median total equivalent dose (EQD2) of combined EBRT and HDR-ICBT to the rectum (α/β=3) was 68.9 (range, 40.4-81.2) Gy. Twenty-two patients received weekly cisplatin, concomitantly. Median follow-up time was 32.5 (range, 4-78) months. The 2-year local control, disease-free survival and overall survival rates (OS) were 89.9%, 83.3%, and 86.3%,