Physica Medica: European Journal of Medical Physics - Volume 32 - Supplement 1

Conclusions:

ART workflow, based on patients’ daily image and sup-

ported by hybrid algorithms, structures re-mapping and dose accumulation

evaluations, could be integrated with novel predictive models to detect lo-

calized intra-organ displacements. Possible set-up errors could be localized

during a specific treatment session. By using SIS epidemic model applied

to RT, decision making process finalized to a re-planning strategy could be

supported considering predicted PG variation and motion.

http://dx.doi.org/10.1016/j.ejmp.2016.01.134

A.131

EVALUATION OF DOSE COMING FROM RADIOLOGICAL MONITOR IMAGES

TO PACEMAKER IN PATIENT UNDERGOING CYBERKNIFE® TREATMENT

S. Maffei

, L. Iadanza, V. Borzillo, L. D’Ambrosio, S. Imbimbo, M. Mormile,

N. Villani, C. Zambella, V. Cerciello.

Istituto Nazionale Tumori, Fondazione G.

Pascale, Napoli, Italy

Introduction:

The aim of present work is showing a procedure to evalu-

ate the radiological monitor dose to pacemaker of patient undergoing

treatment with CyberKnife® (Accuray, Sunnyvale, CA). Radiological monitor

dose is dose coming from radiological images that are generated by x-ray

tubes to monitor patient positioning during radiotherapy dose delivering.

The generation of such images gives patient total dose a contribution that

is not accounted by treatment planning system (tps); tps in fact just takes

into account radiotherapy dose and not even radiological monitor dose. In

some situations this cannot be overlooked and it has to be accounted for;

one of these may be a patient with a pacemaker. For this device manu-

facturer likely indicates a threshold dose value over witch functioning is

compromised. Our patient to be treated with CyberKnife® has a pacemak-

er with a dose threshold value indicated by manufacturer as 2 Gy.

Materials and Methods:

To evaluate dose from radiological monitor images

to the pacemaker we proceed with this tree step way:

1. measurement of dose in air in the same point pacemaker will be placed

during patient treatment;

2. calculation in that same point of ratio between dose to pacemaker and

dose in air; to do so we use Geant4 toolkit for the simulation of the

passage of particles through matter;

3. evaluation of dose to pacemaker multiplying previous ratio by mea-

surement of dose in air.

Results:

We get that dose in air is 0.650 mGy per image couple, and that

the ratio between dose to pacemaker and dose in air is about 3.5; so mul-

tiplying 0.650 by 3.5 and by the total number of monitor image couples

we obtain a estimation of dose to pacemaker.

Conclusions:

The sum of radiotherapy dose calculated by tps (1.4 Gy) and

radiological monitor dose (0.4 Gy) is lower than threshold value of 2 Gy.

The accuracy in evaluation of the dose to the pacemaker can be increased

by knowing the real x-ray tubes emission spectra; we just used a rough

estimation of it.

http://dx.doi.org/10.1016/j.ejmp.2016.01.135

A.132

IS THE OUTCOME OF PROSTATE CANCER PATIENTS TREATED WITH 3D

CONFORMAL RADIOTHERAPY INFLUENCED BY RECTAL/BLADDER

PREPARATION?

A. Maggio

* , a ,

E. Garibaldi

b ,

D. Gabriele

c ,

S. Bresciani

a ,

E. Delmastro

b ,

A. Di Dia

a ,

A. Miranti

a ,

M. Poli

a ,

P. Gabriele

b ,

M. Stas

i a .

Medical Physic

Department, Candiolo Cancer Institute – FPO, IRCCS, Candiolo, Italy;

Radiotherapy Department, Candiolo Cancer Institute – FPO, IRCCS, Candiolo,

Italy;

Neuroscience Department, Physiology Unit, University of Torino, Torino,

Italy

Purpose:

To test the hypothesis that Cancer Specific Overall Survival (CSOS),

Clinical Disease Free (CDFS) and Biochemical Disease free Survival (BDFS)

are influenced by rectal/bladder preparation

Material and Methods:

From 1999 to 2012, 1080 prostate cancer pa-

tients (PCa) were treated with 3DCRT. 761 patients (pts) were treated with

empty rectum and comfortable full bladder while for 319 pts no rectal/

bladder preparation (NRBP) protocol was adopted. The mean prescribed

dose was 76

2 Gy. The mean follow-up was 81

39 months. Survival anal-

ysis was performed by Kaplan–Meier method. Comparison between groups

was performed by the log–rank test. Cox proportional hazards model was

applied for univariate (UVA) and multivariate analysis (MVA) while Hazard

Ratio (HR) allowed to measure how rapidly an event occurs.

Results:

Pts with rectal/bladder preparation (RBP) have significantly lower

risk of dying of PCa, lower biochemical and clinical failures rates respect

to NRBP pts (p

0.0001). At 140 months for RBP and NRPB, the CSOS was

95% vs 85%, the CDFS was 81% vs 71%, the BDFS was 64% vs 48%, respec-

tively. In MVA, for CSOS the Gleason Score (GS) and RBP predicted for death

from PCa; for CDSF and BDFS the GS, D’Amico Risk, PSA, dose

75 Gy, clin-

ical stage and RBP predicted for clinical and biochemical failures. MVA

indicates that RBP is an independent risk factor for biochemical failure

0.003, HR

0.6) while it is the strongest risk factor for clinical fail-

ures and PCa deaths (p

0.0001, HR

0.5). No statistical significant difference

in rectal volume between RBP (mean volume 62.4

24.5 cc) and NRPB (mean

volume 63.4

27 cc) was observed (p

0.52).

Conclusion:

We found strong evidence that rectal/bladder preparation sig-

nificantly decreased (HR

0.6, b

< −

0.5) the probability of death from PCa,

biochemical and clinical failures in pts treated with 3DCRT for PCa, pre-

sumably because pts with RBP are able to maintain a reproducible empty

rectum and comfortable full bladder for all the treatment.

http://dx.doi.org/10.1016/j.ejmp.2016.01.136

A.133

DOSIMETRIC COMPARISON OF EXTERNAL BEAM RADIOTHERAPY WITH

3DCRT, FORWARD-PLANNING IMRT AND VOLUMETRIC ARC THERAPY

(VMAT) IN PANCREATIC CANCER

A. Mameli

, E. Infusino, L. Bellesi, D. Gaudino, G. Stimato, C. Di Venanzio,

M. Fiore, B. Floreno, P. Matteucci, A. Carnevale, S. Ramella,

R.M. D’angelillo.

Universita’ Campus Biomedico, Roma, Italy

Purpose:

To evaluate conformity, homogeneity and dose distribution to PTV

and organ at risk (OAR) of three different types of radiotherapy tech-

niques in pancreatic cancer.

Materials and Methods:

Three radiotherapy treatment plans, including

3DCRT, forward-planning IMRT and volumetric arc therapy (VMAT) were

created for 18 consecutive patients with pancreatic cancer. Dose Volume

Histogram (DVH) comparative analysis was performed for PTV and OAR.

Paired t-test was used for statistical analysis.

Results:

All plans exhibited similar PTV coverage (V95%) and conformity

(all p

0.05). The Homogeneity Index (HI) was acceptable for all plans; in

particular, it was higher in VMAT plans than in 3D-CRT and IMRT plans.

The mean dose to the liver was 13.5 Gy for 3D, 12.1 Gy for IMRT, 10.9 Gy

for VMAT (p

0.001) to the benefit of VMAT. Volumes of kidneys irradi-

ated to doses of 20 Gy (V20), 23 Gy (V23), 28 Gy (V28) by the VMAT plans

were significantly less than those of the IMRT and 3D-CRT plans. The volume

of kidneys irradiated to a dose of 12 Gy (V12) was not significantly differ-

ent comparing the three techniques. Mean of the maximum point dose to

spinal cord was better in VMAT plans (3D-CRT vs IMRT vs VMAT, 30.6 Gy,

34.1 Gy, 26.5 Gy, respectively; p

0.001).

Conclusions:

VMAT can be a better option in treating pancreatic cancer

as compared to IMRT and 3D-CRT. The VMAT plans resulted in equivalent

or superior dose distribution with a reduction in the dose to organ at risk.

http://dx.doi.org/10.1016/j.ejmp.2016.01.137

A.134

MULTICENTER EVALUATION OF THE DOSIMETRIC CHARACTERIZATION

OF LINAC SMALL BEAMS USING A PLASTIC SCINTILLATOR DETECTOR

P. Mancosu

* , a ,

V. Ardu

b ,

G. Benecchi

c ,

C. Gasperri

d ,

S. Linsalata

e ,

G. Loi

f ,

E. Menghi

g ,

E. Mone

s f ,

R. Nigr

o h ,

F. Palleri

c ,

M. Pasquino

i ,

C. Pellegrin

i b ,

S. Riccardi

h ,

L. Spiazzi

j ,

M. Stasi

i .

Radiotherapy Department, Humanitas,

Milano, Italy;

Radiotherapy Department, Policlinico San Donato, San Donato

M.se

, Italy;

Medical Physics Department, AO Parma, Parma, Italy;

Radiotherapy Department, USL 8 Arezzo, Arezzo, Italy;

Medical Physics

Department, USL Lucca, Lucca, Italy;

Medical Physics Department, AOU

Maggiore delle Carità, Novara, Italy;

Medical Physics Department, I.R.S.T.,

Meldola, Italy;

Radiotherapy Department, O.G.P. S.Camillo de Lellis, Rieti, Italy;

AO Ordine Mauriziano Medical Physics Department, Torino, Italy;

Radiotherapy

Department, AO Treviglio e Caravaggio, Treviglio, Italy

e39

Abstracts/Physica Medica 32 (2016) e1–e70