ESTRO 36 Abstract Book

S976 ESTRO 36 _______________________________________________________________________________________________

Conclusion The pilot study demonstrated the feasibility of randomization between treatment with IGRT alone vs IGRT + HDR boost. Treatment compliance was good including adherence quality assurance. EP-1775 Acute toxicity in early cancer prostate patients: low dose rate vs high dose rate monotherapy. S. Rodríguez Villalba 1 , A. Otal Palacín 1 , J. Richart Sanchez 1 , J. Pérez-Calatayud 2,3 , M. Santos Ortega 1 1 Clinica Benidorm, Radiotherapy Department, Benidorm, Spain 2 Clinica Benidorm and Hospital La Fe, Radiotherapy Department, Benidorm, Spain 3 Hospital La Fe, Radiothetherapy Department, Valencia, Spain Purpose or Objective Brachytherapy (BT) in their two modalities, Low dose rate (LDR) and High Dose Rate (HDR) are used in prostate cancer. At present, all available clinical data regarding these two techniques suggests that they are equally effective, providing high tumor control rates. We compare our experience considering acute toxicity in patients with low or intermediate stages treated with LDR BT or HDR BT in monotherapy. Material and Methods Between January 2004 and June 2016 we have treated 113 patients with BT as an exclusively treatment, 85 patients with permanent LDR with Iodine-125 seeds and 28 with HDR Ir-192. Both modalities were performed using ultrasound based intraoperative techniques. Results LDR BT PATIENTS: Median age 68 years (48-81 y), median Gleason 5 (2-7), median value of PSA at diagnosis 7,3 ng/ml (2,5-16,3). 70 patients (82%) low risk (DÁmico classification) and 15 (18%) intermediate risk. In 25 cases (29%) the prescription dose was 145 Gy and in 60 (71%) 160 Gy. Thirty-three (39%) received hormonal treatment. HDR BT PATIENTS: Median age 70,5 years (55-80 y), median Gleason 6 (3-8), median value of PSA at diagnosis 9,08 ng/ml (3-19,75). 12 patients (42%) low risk (DÁmico classification) and 16 (58%) intermediate risk. All patients were treated with 2 applications of 13,5 Gy in monotherapy. Twenty (71%) received hormonal treatment. We analyze the acute toxicity of both treatments following criteria CTCEV.3 and the results are presented on the table. There are not Grade 3 o 4 acute toxicity.

Conclusion In this analyses the acute genitourinary toxicity was higher when the patient were treated with LDR BT including 2 patients (3%) who needed urinary catheter after the implant. We did not find any differences in gastrointestinal toxicity with and excellent tolerance in both groups.

Electronic Poster: Brachytherapy: Gynaecolgy

EP-1776 Is a single CT plan for vaginal cylinder brachytherapy adequate? M. Zahra 1 , M. Doak 1 , W. Keough 2 1 Western General Hospital- Edinburgh Cancer Centre, Clinical Oncology, Edinburgh, United Kingdom 2 Western General Hospital- Edinburgh Cancer Centre, medical Physics, Edinburgh, United Kingdom Purpose or Objective To assess if the target coverage and dose to organs at risk (OARs) from a vaginal vault brachytherapy CT plan are representative of dose delivered during the actual treatment. Material and Methods 28 patients scheduled for post-operative vaginal vault brachytherapy had an initial planning CT scan (CT1) done a few days before the first fraction, with the vaginal cylinder in-situ to generate a treatment plan. The PTV was the cranial 4cm of the vagina to a depth of 0.5cm, and the OARs outlined included the rectum, sigmoid, small bowel and bladder. On the day of the first fraction the patients has a second CT scan with the vaginal cylinder (CT2) and the PTV and OARs were outlined. Then the plan from CT1 was superimposed on CT2 to assess for variation in V100 and d90 to the PTV and the d2cc to the OARs. Prescribed dose was 21Gy in 3 fractions to the PTV, aiming for a V100 of >95% and d90 of 7Gy per fraction. Results Total of 56 scans were analysed. Mean PTV V100 for CT1: 95.8% (range 99.6% - 83.2%); CT2: 96% (range 99.8% – 90%). Mean d90 for CT1: 7.4Gy( range 7.8 – 6.7Gy); CT2: 7.3Gy (range 7.9 – 6.3Gy). Mean difference in d90 per fraction was 0.23 Gy per fraction (range: 0.56 – 0.01Gy).

Small Bowel 3.16 (range 7.0 3.18 (range 6.8 0.3)

Sigmoid Rectum Bladder

4.1 (range 6.4 - 1.9) 3.8 (range 5.9 - 1.4)

5.5 (rnage 7.0 - 3.9) 5.6 (range 7.1 - 3.6)

6.0 (range 6.7 - 4.9) 6.0 (range 7.2 - 4.9)

GRADE 1 LDR/HD R

GRADE 2 LDR/HD R

Mean d2cc (Gy) CT1

GRADE

0

-

LDR/HDR

HAEMATURIA

100%/ 100% 0%/ 0% 0%/ 0%

Mean d2cc (Gy) CT2

CYSTITIS

35%/ 100%

3%/ 0% 21%/ 0%

-

0.3)

INCONTINENCY URYNARY OBSTRUCCION URYNARY

97%/ 87%

0%/ 8% 3%/ 4%

Man difference in d2cc between CT1 and CT2

0.8

0.7

0.9

0.5

60%/ 100% 15%/ 0% 30%/0%

Conclusion The variation in d2cc doses when using the initial CT plan on the second scan taken on the day of the first fraction were minimal and not clinically significant. Differences in PTV coverage are mostly due to slight differences in PTV outlining mainly because of changes in the angle of the cylinder compared to the treatment couch. There does not appear to be the need to plan every single fraction for post-operative vaginal vault brachytherapy as the dosimetry using the initial plan was representative of the dose delivered on the day of treatment.

URINARY FRECUENCY/URGEN CY

41%/ 96%

9%/ 0% 47%/ 4%

URINARY RETENTION 94%/ 100%

3%/ 0% 3%/ 0%

DIARRHEA

94%/ 100% 3%/ 0% 3%/ 0%

RECTAL INCONTINENCY

100%/ 100% 0%/ 0% 0%/ 0%

RECTITIS

94%/ 96% 6%/ 4% 0%/ 0%