Static beam tomotherapy (TD) as an optimisation method in whole breast

radiation therapy (WBRT)Squires, M (BMRS (RT) MA MIR JP MBA(cand.)), Cheers, S (BAppSc (MRS)), Fong, A

(BSc(Med) MB BS MeH FRANZCR), Archibald-Heeren, B (BMRS (RT)), Hu, Y (BMP MSc), Teh, A (BSc(Med) MB BS (Hons) FRANZCR)

• The linear accelerator traditionally used in whole breast radiation therapy • Is tomotherapy a viable alternative?

Background

• What is tomotherapy?

Background

Background

• Traditional tangents• Helical (tomo / VMAT)• TomoDirect

Background

To evaluate static beam tomotherapy (TD) as a method of dose optimisation for the delivery of whole breast radiation therapy (WBRT)

Aim

• Treatment plans of 27 women previously optimised on RayStation v4.5 (RaySearch, Stockholm, Sweden) were replanned using TomoDirect (Accuray, Sunnyvale, California)

Methods and Materials

• A simple medial and lateral beam arrangement was utilised, with no OARs included in optimisation• A ring volume (+0.2cm-+2.0cm) was used to control integral dose.

Prescriptions were normalised to 50Gy and planning time recorded

Methods and Materials

• TD parameters included a field width of 2.5cm, a (default) pitch of 0.251 and a modulation factor of 2.000

Methods and Materials

• Both modalities fell within ICRU62 target homogeneity objectives• Median

TD = 51.1Gy vs IMRT = 50.9Gy, p=0.03

• D1 TD = 53.5Gy vs IMRT = 53.0Gy, p=0.02

• Homogeneity index (HI) TD = 0.11 vs IMRT = 0.10, p=0.03

Results

• Both modalities fell within ICRU62 target homogeneity objectives• VTD

TD = 85.5% vs IMRT = 82.0%, p=0.09 (No significant difference)

• D99 TD = 48.0Gy vs IMRT = 48.1Gy, p=0.26(No significant difference)

Results

• TD plans produced a statistically significant reduction in V5 ipsilateral lung doses

TD V5 = 23.2% vs IMRT = 27.2%, p=0.04

• TD reduced planning time considerably TD = 9.8m vs IMRT = 27.6m, p<0.01 saving an average planning time of 17.8 minutes per patient

Results

• Other queried OAR metrics remained statistically comparable

• Ipsilateral lung TD V20 = 13.2% vs IMRT = 14.6%, p=0.30

• Heart TD V5 = 2.7% vs IMRT = 2.8%, p=0.47 TD V10 = 1.7% vs IMRT = 1.8%, p=0.44

Results

Conclusion

Static beam tomotherapy (TD) can provide a superior method of whole breast radiation therapy (WBRT):

• Comparable target metrics • A reduced ipsilateral lung dose• A reduced user optimisation time

ROC Gosford

[1] Fields E, Rabinovitch R, Ryan N, Miften M, Westerly D 2013, ‘Á detailed evaluation of TomoDirect 3DCRT planning for whole-breast radiation therapy.’ Medical Dosimetry 38: 401-406[2] Franco P, Catuzzo P, Cante D, La Porta MR, Sciacero P, Girelli G, Casanova Borca, V, Pasquino M, Numico G, Tofani S, Meloni T, Ricardi U, Ozzello F 2011, ‘TomoDirect: an efficient means to deliver radiation at static angles with tomotherapy.’ Tumori 97: 498-502[3] Franco P, Ricardi U 2012, ‘Tomo Direct to deliver static angle tomotherapy treatments.’ Nuclear Medicine and Radiation Therapy 3:5

References & Acknowledgements