The feasibility of a QA program for ISIORT Trials

(1)

Baveno, Italy June 22-24, 2012

The feasibility of a QA program

for ISIORT Trials

Frank W. Hensley1_{, Don A. Goer}2_{, Sebastian Adamczyk}3_{, Falk Roeder}1_,

Felix Sedlmayer4_{, Peter Kopp}4

1_{University Clinics Heidelberg, Dept. of Radiation Oncology, D 69120 Heidelberg, Germany} 2_{Intraop Medical Company, 570 Del Rey Avenue, Sunnyvale, CA 94085, USA}

3_{Medical Physics Department, Greater Poland Cancer Centre, 61-866 Poznań, Poland} 4_{University Hospital Salzburg, Dept. of Radiation Oncology, 5020 Salzburg, Austria}

(2)

Issue :

Can we design a QA protocol for IORT trials

which assures that IORT patients treated

- at different centers

- with different IORT and EBRT accelerators

all recieve the protocol prescription

so that the analysis of clinical results is meaningful ?

(3)

FWH ISIORT Baveno 2012 3

HIOB trial:

Hypofractionated Whole-Breast Irradiation preceded by

Intra-Operative Radiotherapy with Electrons as anticipated Boost

prospective, non- randomised multi-center trial

to test the combination of

an advanced IORT boost

11.1Gy @ Dmax ( = 10Gy @ 90%)

combined with

- consecutive hypofractionionated EBRT

15 x 2.7 Gy = 40.5 Gy

(4)

The HIOB protocol requires QA for:

• Target preparation

• Selection of applicator and beam energy

for IORT

• Documentation of IORT

• Documentation of standardized WBRT

(and, of course, criteria for patient selection, combination with chemotherapy, etc.)

(5)

Target

• coverage of complete target with prescribed dose at 90% isodose

• selection of applicator • selection of beam energy + documentation of all steps

Target preparation

(6)

HIOB:

measure and report:

• target diameter

= 3D volume of tissue reaching

at least 2 cm beyond the former macroscopic tumor edge

(excluding skin)

• depth of distal margin of target ( = depth to pectoralis)

measured preferably by intraoperative sonography or (mobile) CT

• depth of rib

Dose limit to anterior rib surface: 5 Gy pectoralis

(7)

HIOB: dose prescription

• IOERT Dose (11.1 Gy) is specified at the point of maximum dose on the central axis depth dose curve.

• The PTV should be encompassed by 90% of the prescribed dose (i.e. 10 Gy).

• A dose inhomogeneity of -10% within the target volume is acceptable.

In the beam entrance region, small volumes of underdosage down to 80% are acceptable

(8)

HIOB : selection of applicator

Typical electron dose distribution:

80-90% region

~ 1cm smaller

than diam. of applicator

 Applicator diameter must be

min. 1cm larger than target

Different for different types of acclerators

Hiob participants must therefore report parameters of

dose distributions for all energies and

(9)

d_rib- d_pectoralis

HIOB: selection of electron energy

governed by:

- targe coverage by 90%-isodose

- dose limit to anterior rib surface: 5 Gy thickness of pectoralis typiclly ~ 1cm

R₈₀ -

(10)

HIOB: dosimetric QA

• Calibration of the EBRT & IOERT beams according to one of the dosimetry protocols: IAEA TRS 398, TG 51, OeNORM S5234-3 or DIN 6800-2, and identify which protocol is being used.

• Initial MU calibration - verified by transfer dosimetry (e.g. TLD) in cooperation with an accredited dosimetry laboratory. Participants in the USA encouraged to use the RPC mailed TLD program.

• Beam output constancy for mobile & stationary IOERT units - method and frequency of measurement varies depending on the type of system in use, but all methods assure the output is constant to +/- 3% per AAPM TG 72, and that the 90% depth dose is within 2 mm of the initial calibration.

• EBRT x-ray output of the energy used must be validated weekly to assure that the precision of dose to the reference point is within +/- 2%.

(11)

FWH 03 / 2012

IOERT _WS FFM 07.03.12 11

Tägliche QA :

Einfacher reproduzierbarer Aufbau

• schneller Aufbau

• möglichst geringer Dosisverbrauch

(12)

Einfacher reproduzierbarer Aufbau

(13)

FWH 03 / 2012

Notwendige Dosis für Prüfung

hängt ab von:

– Linearität des Monitors

– Reproduzierbarkeit der Abschaltdosis

Ziel :

Dosisunsicherheit im Referenzpunkt <

±

2 -2.5 %

(14)

Arbeitstägliche QA

Reproduzierbarkeit der Monitordosis

(15)

FWH 03 / 2012

Reproduzierbarkeit der Abschaltdosis

• Min. 3 Messungen bei jeder Energie

• Dosis 10Gy (wie therapeutische Dosis)

 120 Gy QA-Dosis pro Tag

bei Betriebsbelastung 380 Gy / Woche

(16)

Stabilität der Elektronenenergie

Möglicherweise Änderungen aufgrund von

Energieänderungen im flexiblen Hohlleiter

 regelmäßige Überprüfung der e

-

_-Energie

(17)

FWH 03 / 2012

Filmdosimetrie mit Radiochrom- Filmen

(18)

HIOB: WBRT

Time factors

WBRT starts after day 36 p.o. but until day 56 p.o.(in case of adjuvant hormonal treatment or no further tumor specific medication)

In case of adjuvant chemotherapy, a time – gap between IOERT and WBRT up to 6 months is allowed

Treatment technique

• PTV - whole breast gland with the adjacent chest-wall

• 3D CRT (tangential wedged fields or IMRT) on individual CT-slices

• WBRT - delivered by photons – with a minimum energy of 4 MV on Linacs • Weekly patient set-up verification

Dosage and duration of WBRT

• Single fx dose = 2,7 Gy (ICRU)

• 15 fx – 5 fx/week with regular RT-breaks (weekend/feast days) • V20 < 20 % of ipsilateral lung

• D50% < 5% of heart volume

First WBRT treatment plan and portal images are analyze by the HIOB QA team to ensure compliance with the protocol. Subsequent treatment plans randomly review by the HIOB QA

(19)

Example: dose distribution for a patient treated

according to QA protocol

IORT

: Pat. 1 48y pT1 tumor Diameter : 19 mm complete resection  Target diameter ≤ 40mm target thickness : 20 mm depth rib : 28 mm 40 mm 20 mm 28 mm

Energy:

10 MeV

Applicator:

5cm straight

(20)

(21)

Example: dose distribution for a patient treated

according to QA protocol

(22)

Example: dose distribution for a patient treated

according to QA protocol

(23)

Example: dose distribution for a patient treated

according to QA protocol

IORT

: Pat. 2 66y pT1 tumor Diameter : 12 mm complete resection  Target diameter ≤ 40mm target thickness : 16 mm

Shielding plate diameter : 70 mm

Shielding plate thickness : 5 mm Shielding plate H₂O equivalent : 20 mm

40 mm

16 mm

Energy:

6 MeV

(24)

Example: dose distribution for a patient treated

according to QA protocol

(25)

Conclusion

It is possible to develop a practical

QA program to assure proper

radiation delivery for an ISIORT

(26)

Thank you for your attention

and …

Find also:

Intraoperative radiotherapy in breast cancer treatment using high energy electrons – four years of experience - Sebastian Adamczyk, Marcin Litoborski – poster presentation