{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

HYPO_HSR - Hypofractionation with Tomotherapy experience at...

Info icon This preview shows pages 1–10. Sign up to view the full content.

View Full Document Right Arrow Icon
Hypofractionation with Hypofractionation with Tomotherapy: experience at HSR Tomotherapy: experience at HSR Radiation Therapy DPT, San Raffaele Hospital, IRCCS Milano, Italy Di Muzio Nadia Napoli 8-9 Giugno 2009
Image of page 1

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Summary Summary Classical applied radiobiology Hypofractionated RT: pro’s and con’s Hypofractionated protocols at HSR Lung mets (details) Liver mets (details) Pancreatic carcinoma (details) Pleural Mesothelioma (details) ….. further informations in other course lessons (head- neck, prostate, etc) Conclusions
Image of page 2
The effect of radiation on cells is described by the Linear-Quadratic (LQ) model – extensively verified provided d > 0.5 Gy and dose-rate not too low Radiobiological basis: from the beginning between - in recovery full ) ( ) ( 2 E e SF and d D d d n E - = + = + = β α β α where the α and β are coefficients which describe the radiosensitivity of the cells in the normal tissue /tumour
Image of page 3

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Using different fractionation regimens the model enables one to convert from one regimen to another, by equating BED Classical applied radiobiology: BED BED= E/ α = D[1+d/( α / β )] Biological Effective Dose Basic assumptions: - Complete repair of sublethal damage between fractions - The effects of proliferation are negligible - Dose distributions are uniform
Image of page 4
In case of rapid repopulation during treatment: Classical applied radiobiology: BED BED= E/ α = D[1+d/( α / β )]-h(T-T K ) T= Overall treatment time (days) T k =Proliferation starts at T k days (20-30 days) h=0.4-0.8 Gy/day: Rate of loss after T k For tumours with rapid repopulation during treatment the reduction in overall treatment time could increase the local control
Image of page 5

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
To convert a total dose D given in fractions of size d into the isoeffective total dose EQD 2 given in 2-Gy fractions β α β α + + = = 2 D E 2 assuming 2Gy d D Q d ref Classical applied radiobiology: EQD 2 Withers formula (assuming complete repair, negligible repopulation, etc.) d and D are the doses prescribed for the tumour (…nothing about dose distribution and OAR behaviour)
Image of page 6
Classical applied radiobiology: α and β α / β (Gy): ratio used in the LQ model to quantify the fractionation sensitivity of tissues Normal Tissues: - Low α / β (0.5-6 Gy) late effects, expressed months to years after irradiation - High α / β (7-20Gy) acute effects, expressed within a period of days to weeks after irradiation Tumours: - High α / β (7-20Gy) (few exception in melanomas, sarcomas, prostate (?))
Image of page 7

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
But don’t forget the assumptions the absorbed dose of the OAR is the same than the absorbed dose of the tumour: while it’s quite obvious the fact that if we can half the dose to the OAR we could double the dose/fraction without any incremental risk for the OARs • No differences have been considered between serial and parallel organs: while the volume effect could have a great influence in the determination of the toxicity of the treatment in all the parallel OARs
Image of page 8
Hypofractionation: PRO’S square4 Potentially favourable with tumours with high rate of repopulation during treatments square4 Favourable for tumour with α / β smaller than α
Image of page 9

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 10
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern