ESTRO 31 S427

initially drawn on the PTV margins, and were then gradually expanded

(in steps of 5 mm) up to achievement of the following dose/volume

constraint: D98%> 95%. The distances of the field edges from bony

landmarks and anterior rectal wall were measured. The same

procedure was repeated using 6-MV photon beams and beams

produced by a telecobalt unit.

Results: The results of the analysis are shown in the table. Reported

measures (in millimetres) represents the minimum distance able to

meet the PTV constraint in 4/5 patients.

fields margin

beams

Cobalt

60

6

MV

15

MV

anterior-

posterior

lateral from the center of the

symphysis pubis (laterally)

70 55 55

inferior from the bottom of ischial

tuberosities (below)

20 5 5

superior from the top of the

symphysis pubis (above)

60 50 50

lateral anterior from the posterior margin

of the symphysis pubis

(posteriorly)

25 20 20

posterior from the most anterior

point of the rectum

(posteriorly)

50 45 45

Conclusions: Using a group of patients with 'large' PTV, based on a 3D

dosimetric evaluation, we propose new indications for 2D treatment

of high risk CAP, based on current criteria for definition of risk

category (NCCN), CTV (EORTC) and PTV.

EP-1104

IS OBESITY CORRELATED WITH GASTROINTESTINAL TOXICITY INDUCED

BY RADIOTHERAPY FOR PROSTATE CANCER?

H. Doi1

, F. Ishimaru2

, M. Tanooka1

, H. Miura1

, H. Inoue1

, Y. Takada1

,

M. Fujiwara1

, S. Yamamoto3

, N. Kamikonya1

, S. Hirota1

1

Hyogo College of Medicine, Department of Radiology, Nishinomiya,

Japan

2

The Hospital of Hyogo College of Medicine, Department of Clinical

Radiology, Nishinomiya, Japan

3

Hyogo College of Medicine, Department of Urology, Nishinomiya,

Japan

Purpose/Objective: There are only a few reports about the

correlation between radiation-induced gastrointestinal (GI) toxicity

and obesity. The purpose of the present study is to determine the

impact of obesity on GI toxicity.

Materials and Methods: 181 patients with prostate cancer were

treated with radiotherapy (RT) from 2008 to 2009. 27 patients with

prostate cancer were treated with three-dimensional conformal RT as

a primary therapy, and had the available data. The median age was

72.3 years, median initial PSA was 74.6 ng/mL, and median Gleason

score was 8.1. RT was delivered to prostate with or without seminal

vesicle. Dosimetric parameters included V40, V50, V60, V65 and V70

of the rectum, and the mean dose of PTV. The distance between the

rectum and the prostate, the abdominal circumference, the area of

subcutaneous fat, and the area of visceral fat were obtained from the

data of CT scanning. GI toxicity was assessed regarding the acute

symptoms induced by RT. The results were compared according to

patients without any GI toxicity (Group A) or patients with GI toxicity

(Group B), as applicable.

Results: Group A contained 19 patients. Group B contained the

remaining 8 patients. There were no patients with grade 3 or greater

toxicities. The results are shown in the Table. Higher BMI and larger

area of subcutaneous fat had a tendency to decrease the incidence of

GI toxicity in the present study, although there were no significant

differences between the groups in all criteria.

Conclusions: Our study demonstrated that acute GI toxicity induced

by RT was likely associated with BMI and the subcutaneous fat.

EP-1105

A LOW-DOSE RATE PROSTATE BRACHYTHERAPY POST-IMPLANT

SECTORS EVALUATION

C. Chiumento1

, A. Fiorentino1

, R. Caivano1

, M. Cozzolino1

, S.

Clemente1

, P. Pedicini1

, V. Fusco1

1

I.R.C.C.S.-CROB, Radiotherapy Department, Rionero in Vulture, Italy

Purpose/Objective: The aim of this study was to compare post

implant doses delivered to benign and malignant sectors of prostate

gland after low-dose rate prostate brachytherapy in patients with no

evidence of biochemical disease.

Materials and Methods: Patients with low and intermediate prostate

cancer (D’Amico risk classification) treated with I-125 monotherapy to

a prescribe dose of 145 Gy were evaluated. Inclusion criteria were a

prostate biopsy from six sectors of gland (right and left portion of the

base, mid-gland and apex), a CT post-implant dosimetry performed 7

weeks after implants, neo-adjuvant hormonal therapy ≤ 6 months and

no biochemical evidence disease at last follow-up. Prostate gland in

six anatomical regions called 'sectors' corresponding to biopsy sites

was divided.

Sectors analysis was performed evaluating D100 (dose delivered to 100

% of the volume) on post-implant CT scan of each sector .D100 min,

D100 max and D100 median for benign and malignant sectors were

obtained.

Results: From June 2003 to October 2009, 61 pts were retrospectively

assessed, with a median follow-up time of 64 months (range13-101).

All pts were free from biochemical disease.

There were 238 benign sectors and 128 malignant sectors. Benign and

malignant sectors were distributed in 40%, 25%, 35% and 20%, 49%,

31% with respect to prostate base, mid-gland and apex. D100 min,

D100 max, D100 median of 50.3 Gy, 182.68 Gy , 91.856 Gy and 52.6

Gy,181.9 Gy and 96.275 Gy from a post implant CT dosimetry scan

were obtained for benign and malignant sectors respectively.

Conclusions: We observed a good clinical outcome in pts with clinical

localized prostate cancer treated with low-dose rate brachytherapy,

although the median D100 post implant was lower than the

prescription dose. Further dose de-escalation studies would be

performed in this setting of patients.

EP-1106

NO ADDITIONAL VALUE OF MRI TO ULTRASOUND IMAGING IN EXTERNAL

BEAM TREATMENT PLANNING OF LOCALIZED PROSTATE CANCER

W. Grootjans1

, C.J.M. Hoekstra1

, S.M.G. van de Pol1

, H. Westendorp1

,

A.W.H. Minken1

1

RISO, Radiotherapy, Deventer, The Netherlands;

Purpose/Objective: The purpose of this study was to assess the added

value of MRI with respect to transrectal ultrasound (TRUS) imaging for

treatment planning of localized prostate cancer.

Materials and Methods: Nine patients with intermediate and high risk

localized adenocarcinoma of the prostate, who received EBRT

treatment at our institute, were included in this study. One

experienced radiation oncologist delineated the prostate CTV on MRI

and TRUS images combined with CT information. We analyzed the

contour variability and spatial conformity by using the Jaccard-index.

Dose coverage of different prostate segments (base, mid-gland and

apex) is quantified by assessing the dose delivered to the delineated

target volumes on TRUS and MRI.

S428 ESTRO 31

Results Delineation on neither one of the imaging modalities resulted

in significantly larger or smaller prostate volumes (average MRI/TRUS

volume ratio: 0.94±0.11). In general, the MRI and TRUS contours were

highly similar in the postero- and anterolateral regions of the prostate

mid-gland segment. In most patients, the conformity of the TRUS and

MRI delineations decreased near the base of the seminal vesicles and

prostate apex. Analysis of MRI and TRUS contour variability reveals

that the encountered contour deviations are in the range of 2 to 5

mm. The mean values of the Jaccard-index for the mid-gland/apex

and mid-gland segments are respectively 0.77±0.05 and 0.81±0.05,

indicating good spatial conformity of the defined target volumes. MRI

and TRUS delineated CTVs were equally covered. The mean difference

in the V95% (volume receiving 95% of prescription dose) value of the

MRI and TRUS derived CTVs for the mid-gland/apex and mid-gland

segment of the prostate is respectively 1.07%±0.69 and 1.02%±0.69.

The minimum dose of the MRI derived CTV is consistently lower

compared to the minimum dose of the TRUS derived CTV. The mean

difference in minimum dose between these CTVs is 3.47%±3.06.

Conclusions: The MRI and TRUS prostate delineations demonstrate a

high degree of similarity and spatial conformity. There are no

differences in dose coverage of the TRUS and MRI derived CTVs. These

results indicate a limited additional value of MR imaging for the

purpose of planning in EBRT treatment of localized prostate cancer

for this observer.

EP-1107

HYPOFRACTIONATED IMRT TO PROSTATE AND PELVIC LYMPH NODES:

ANALYSIS OF ACUTE TOXICITY

A. Martin1

, P. Treasure1

, R. Verma1

, P. Ostler1

, P. Hoskin1

, N.

Anyamene1

, R. Alonzi1

, R. Hughes1

1

Mount Vernon Cancer Centre, Radiotherapy, London, United Kingdom

Purpose/Objective: Hypofractionated radiotherapy schedules have

potential benefits in the treatment of prostate cancer. Published data

have demonstrated acceptable acute toxicity when delivering

hypofractionated radiotherapy to the prostate alone. The toxicities

associated with delivering hypofractionation to larger pelvic

treatment fields are unclear.

Materials and Methods: 33 patients with locally advanced prostate

cancer (LAPC) and a predicted pelvic lymph node involvement risk of

greater than 20 %, treated at this institution between May 2010 and

September 2011, were prescribed a standardised IMRT protocol of 60

Gy in 20 fractions over 28 days to the prostate and seminal vesicles,

with 47 Gy in 20 fractions to the pelvic lymph nodes delivered

concurrently. 3 patients received an in-field boost of 52 Gy in 20

fractions to radiologically enlarged nodes. Acute radiotherapy toxicity

data were collected prospectively pre-treatment, then weekly during

treatment and at 6 weeks post radiotherapy, using the EORTC/RTOG

Common Toxicity Criteria for skin, GI and GU toxicity. All patients

remain on androgen suppression.

Results: Acute toxicity data during radiotherapy are available for 32

patients, 28 of whom also had a toxicity assessment at 6 weeks post

treatment (see Table 1). Only 1 of 32 patients (3 %) experienced grade

3 toxicity (diarrhoea): this resolved to grade 2 by 6 weeks. All other

toxicities seen were grade 1-2 in severity. The most common

symptoms were dysuria (affecting 75 % patients) and diarrhoea (59 %),

however these decreased to 21 % and 7 % respectively at 6 weeks post

treatment. Acute toxicity peaked during the final week of

radiotherapy. No skin toxicity was observed. 32 % patients (9/28) had

no residual toxicity at the 6 week assessment.

Grade 1 Grade 2 Grade 3

Desquamation 0 0 0

Dry Skin 0 0 0

Anorexia 1 (3 %) 0 0

Constipation 2 (6 %) 2 (6 %) 0

Diarrhoea 14 (44 %) 4 (13 %) 1 (3 %)

Proctitis 8 (25 %) 0 0

Vomiting 1 (3 %) 0 0

Haematuria 2 (6 %) 0 0

Pelvic Pain 2 (6 %) 0 0

Dysuria 10 (31 %) 1 (3 %) 0

Urinary Incontinence 1 (3 %) 3 (9 %) 0

Urinary Frequency 23 (72 %) 1 (3 %) 0

Table 1: Number (and percentage) of patients experiencing acute

toxicity during radiotherapy or at 6 weeks post treatment.

Conclusions: Hypofractionated IMRT to prostate and pelvic lymph

nodes is feasible and well-tolerated in the acute setting, with side

effects comparable to that seen with smaller field prostate-only

hypofractionated treatments. The risk of late toxicity is a major

consideration in hypofractionated radiotherapy, therefore further

follow-up is necessary to establish the longer term safety and efficacy

of this treatment regimen.

EP-1108

THE EFFECT OF BOWEL PREPARATION PRIOR TO PLANNING CT ON

RECTAL VOLUME & ISOCENTRE SHIFT DURING PROSTATE

RADIOTHERAPY

L. Pettit1

, K. Tune-Blundell1

, S. Tirmazy1

, P. Ramachandra1

1

New Cross Hospital, Deansley Centre, Wolverhampton, United

Kingdom

Purpose/Objective: The position of the prostate gland varies during

radiotherapy due to rectal distention. A distended rectum on the

planning CT scan may compromise the posterior coverage of the PTV.

This may be due to the prostate moving posteriorly as the rectum

becomes less distended throughout radiotherapy. Rectal distention

has been shown to increase the risk of local and biochemical failure.

The posterior margin is critical given the high frequency of tumors

located within the peripheral zone. PTV margins are generally tighter

posteriorly in order to spare rectal toxicity. At present there is no

consensus for bowel preparation prior to the planning scan. This study

retrospectively compared patients who had a single bowel preparation

(BP) prior to the planning scan to patients who had not.

Materials and Methods: A retrospective review of patients undergoing

radical radiotherapy for prostate cancer was undertaken.

Radiotherapy was verified using a pre treatment cone beam CT (CBCT)

scan (day 0) followed by weekly CBCT’s with an offline correction

protocol. CBCT scans for beginning, mid, and end of treatment were

transferred to the prosoma planning system. The rectum was

contoured and rectal volume calculated. Deviations from the planning

scan were recorded. Isocentre shift and corrections required were

recorded.

Results: Five patients had BP and 8 had no BP. The median age was 71

years in both groups. The median number of CBCT’s was 9.4 in the BP

group and 13.4 in the non BP group. The median rectal volume on the

planning scan was 84 ml in the BP group and 106 ml in the non BP

group. The median deviation from the planning scan was 26.8 ml in

the BP group and 32.5 ml in the non BP group. Median isocentre

movement was 0.35 cm anteriorly in the BP group and 1.76 cm

anteriorly in the non BP group. The median actual isocentre moves

was 1.2 in the BP group and 4.5 in the non BP group. There were two

treatment delays in the non BP group.

Conclusions: A single bowel preparation prior to planning scan leads

to a lower rectal volume on planning scan, less deviation from the

planning scan, fewer CBCT’s, less isocentre shift and less corrections.

This has now been adopted as standard practice in the department.

EP-1109

POSTOPERATIVE RADIOTHERAPY IN PATIENTS WITH BIOCHEMICAL

FAILURE AFTER RADICAL PROSTATECTOMY: CLINICAL OUTCOME

J.G.M. Vemer - van den Hoek1

, P. van Rooij1

, C.H. Bangma2

, S.

Aluwini1

1

Erasmus Medical Centre, Radiation Oncology, Rotterdam, The

Netherlands

2

Erasmus Medical Centre, Urology, Rotterdam, The Netherlands

Purpose/Objective: Radiotherapy (RT) for post-prostatectomy

recurrences of prostate cancer offers a potentially curative treatment

for selected patients, but is still a topic of debate with many

questions to be answered. We evaluate 5 years of clinical outcomes

for this group regarding toxicity and tumor control.

Materials and Methods: A retrospective analysis was performed, in 81

patients treated in our institution with salvage conformal RT on the

prostate bed (68-72 Gy). The radical prostatectomy for stage T2-

4N0M0 prostate cancer was performed in different hospitals.

Results: The mean age was 61.9 years (range, 44-79 years). The mean

interval time between surgery and RT was 44.2 months (range 2-141

months). Mean follow-up was 73.5 months (range 10 - 81.4 months).

Mean preoperative PSA was 15.2 ng/mL (range 1.3 - 68.0 ng/mL),

while the mean recurrence PSA-level before RT was 1.7 ng/mL (range