Abstract Book

S817

ESTRO 37

Material and Methods We investigated examination and treatment results of 148 locally advanced cervical cancer patients treated at Azerbaijan National Center of Oncology from 2015 to 2017. Nineteen patients (12,8%) had adenocarcinoma while 129 (87,2%) had squamous cell carcinoma. Distribution by stages was as following: IIA - 20,3%, IIB - 44,1%, IIIB - 32,2%, IVA - 3,4% patients. Patients received concurrent chemoradiotherapy: external beam radiotherapy (IMRT) by 1,8 Gy fraction to 45, weekly cisplatin (40 mg/m2) and 4 fractions 7 Gy 3D image guided high dose rate brachytherapy. We investigated tumor samples to identify somatic hotspot mutations within the helical or the catalytic domains of PIK3CA gene. Analysis was conducted by RT-PCR method. Response rate was assessed by comparison of the highest tumor size in any direction on pretreatment and after 5 weeks EBRT pre-brachytherapy MRI images. Results We revealed activation of PIK3CA gene in 43 (29,1%) patients totally. PIK3CA mutations were found in four cases (21,1%) of adenocarcinomas and in 39 (30,2%) patients with squamous cell cervical cancer. The predominant mutation sites were E542K and E545K in the helical domain of the PIK3CA gene. Mean tumor shrinkage rate (defined be reduce in tumor’s greatest size) was 79,8% (SD 13,4) in PIK3CA mutated patients and 67,4% (SD 16,5) in wild type PIK3CA patients (p=0,064). Conclusion Our results showed that locally advanced cervical cancer patients with hotspot mutations of PIK3CA had higher tumor response rate (non-significantly) after concurrent chemoradiotherapy than patients without these mutations. Further investigation with a larger dataset is required to validate these findings and to explore probability of PIK3CA signaling pathway inhibitors use in patients with cervical cancer. Acknowledgment. This work was supported by the Science Development Foundation under the President of the Republic of Azerbaijan – Grant № EIF-KETPL-2-2015- 1(25)-56/37/3. EP-1508 FDG-PET/CT and MRI in definitive radiochemotherapy for locally advanced uterine cervical cancer A.C. Waldenström 1 , K. Bergmark 2 , A. Michanek 3 , F. Hashimi 4 , C. Olsson 1 , H. Leonhardt 4 , P. Gjertsson 3 1 University of Gothenburg, Regionalt Cancercentrum RCC väst, Gothenburg, Sweden 2 Sahlgrenska University Hospital, Oncology, Gothenburg, Sweden 3 Sahlgrenska University Hospital, Nuclear Medicine, Gothenburg, Sweden 4 Sahlgrenska University Hospital, Radiology, Gothenburg, Sweden Purpose or Objective In uterine cervical cancer, tumor spread reaching the para-aortic lymph nodes from the primary site in the cervix is the most significant independent pre-treatment predictor of progression-free survival. Introducing a PET- scanner in our hospital, the aim was to investigate how the information from pre-treatment FDG-PET/CT compared to MRI, and how it would affect the prescribed radiation treatment in patients with advanced uterine cervical cancer and relate this to survival. Material and Methods In a prospective study, we investigated 25 consecutive patients with uterine cervical cancer who were planned

OAR EBRT doses are detailed in the table below. Median EBRT duration and overall treatment time (OTT) were 35 (26-43) and 50 (41-72) days, and were not prolonged in 88% and 55%, respectively. Chemotherapy was not completed in 9 (22%) due to hematologic, 5 and GI toxicity, 1; aggravation of pre-existing renal insufficiency, 2; and tumor bleeding, 1. Mean interval between EBRT and IGABT was 10 (3-23) days. EBRT dosimetry did not compromise IGABT CTV-IR dose in any case. Mean nodal cumulative EQD2 doses (Gy) were: PA (n=26) 58.6 ±3.1; UP (n=88) 59.8 ±1.9; LP (n=111) 60.6 ±2.2); and ING (n=3) 60.3 ±0.21. Twelve patients (30%) had grade 3-4 acute toxicity (see table). At a median follow-up of 14 months (3-37), grade 3-4 late GI and GU toxicity was seen in 4 and 2 patients. Three-year DFS and OS rates were 58% and 76%, respectively. Fourteen (35%) recurred; the site of first failure was locoregional + distant in 5; regional + distant, 3; distant only, 3; local + distant, 2; and local only, 1. EBRT Dosimetry and Acute Toxicity Mean OAR doses (Gy) and constraints met (%) Dmax D50% Rectum (Dmax <50Gy, D50% ≤40Gy) 48.0 (85) 41.1 (38)

Bladder (Dmax <50Gy, D50% ≤40Gy) Bowel (Dmax <50Gy, D50% ≤30Gy) Grade 3-4 acute toxicity

39.6 (63) 22.7 (95)

50.9 (50)

52.6 (53)

N

%

Nausea

8

20

Vomiting

1

3

Diarrhea

1

3

Cystitis

8

20

Hematologic

4

10

Conclusion Our outcomes support the feasibility and effectiveness of SINB. With careful attention to OAR constraints, acute toxicity can be limited, treatment compliance preserved, and delivery of sufficient doses during brachytherapy not compromised. EP-1507 Tumor response rate depending on PIK3CA mutation status in Azerbaijanian cervical cancer patients K. Akbarov 1 , I. Isayev 1 , L. Melikova 1 , E. Quliyev 1 , N. Aliyeva 1 1 National Oncological Centre, Radiotherapy, Baku, Azerbaijan Purpose or Objective Cervical cancer is the third most common female cancer in Azerbaijan and the vast majority of these patients apply to the clinic at late stages. Today cisplatin-based concurrent chemoradiotherapy is the standard treatment for locally advanced cervical cancer. But in general the treatment results remains poor and response to treatment varies in a wide range. To define the probability of PIK3CA as an individual prognostic factor we evaluated the frequency of PIK3CA gene mutation and it’s impact on post chemoradiotherapy tumor response rate.