8/2/2017. Improving Dose Prescriptions for Safety, Reporting, and Clinical Guideline Consistency. Part III

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1 Improving Dose Prescriptions for Safety, Reporting, and Clinical Guideline Consistency Part III I Das, J Moran, M Langer Keeping Guidelines On Track: The Effect On Clinical Practice of Neglecting Guidelines for Dose Prescription and Reporting Mark Langer, MD Indiana University School of Medicine AAPM Member Why not go off the rails? Are guidelines followed? Why should the MD care? Why choose ICRU guidelines? How to get back on track? 1

2 allows dose volume-based prescription and reporting. In modern radiation therapy, the specification of the absorbed dose to relevant anatomic volumes rather than to single points is critical to the communication of the treatment intent. guidelines Prescription Format The report does not recommend any particular value of V in D v for a prescription. However, the median absorbed dose, D50 %, is likely to be a good measure of a typical absorbed dose in a relatively homogeneously irradiated tumor. Reporting The report recommends that the median absorbed dose, specified by D50 %, should be reported, as it is considered to correspond best with the previously defined dose at the ICRU reference point. 2

3 Reporting the following definition for homogeneity index is suggested: Das I. et al Practical Radiation Oncology (2017) 7, e145-e155 NRG HN-001 NRG HN-002 3

4 E ICRU 62 Prescription IMRT Planning All plans shall be normalized such that at least 95% of the volume of the PTV is covered by the prescribed isodose surface. Protocol Target Dose Criteria PTV V 100% 95% V 108% 3% D 95 95% D 99 93% Body V 110% 0% NRG HN001 NRG HN Dose Specifications (04May2017) IMRT Dose Prescription to PTVs the PTV69.96 (CTV margin) will receive Gy at 2.12 Gy per fraction. PTV=+11-13mm The treatment goal is that 95% of the volume of all PTVs must receive the prescribed dose minimum dose (defined as dose to 99% of PTVs) PTV V 100% =95% 90% D 99 90% 85% D.03cc 115% 120% PTV D 95=100% 105% D 99 93% 90% D.03cc 110% 115% E ICRU 62 Prescription IMRT Planning All plans shall be normalized such that at least 95% of the volume of the PTV is covered by the prescribed isodose surface. Protocol Target Dose Criteria PTV V 100% 95% V 108% 3% D 95 95% D 99 93% Body V 110% 0% NRG HN001 NRG HN Dose Specifications (04May2017) IMRT Dose Prescription to PTVs the PTV69.96 (CTV margin) will receive Gy at 2.12 Gy per fraction. PTV=+11-13mm The treatment goal is that 95% of the volume of all PTVs must receive the prescribed dose minimum dose (defined as dose to 99% of PTVs) PTV V 100% =95% 90% D 99 90% 85% D.03cc 115% 120% PTV D 95=100% 105% D 99 93% 90% D.03cc 110% 115% E ICRU 62 Prescription IMRT Planning All plans shall be normalized such that at least 95% of the volume of the PTV is covered by the prescribed isodose surface. Protocol Target Dose Criteria PTV V 100% 95% V 108% 3% D 95 95% D 99 93% Body V 110% 0% NRG HN001 NRG HN Dose Specifications (04May2017) IMRT Dose Prescription to PTVs the PTV69.96 (CTV margin) will receive Gy at 2.12 Gy per fraction. PTV=+11-13mm The treatment goal is that 95% of the volume of all PTVs must receive the prescribed dose minimum dose (defined as dose to 99% of PTVs) PTV V 100% =95% 90% D 99 90% 85% D.03cc 115% 120% PTV D 95=100% 105% D 99 93% 90% D.03cc 110% 115% 4

5 E ICRU 62 Reporting Prescription Dose Maximum point dose PTV V 110%,V 110%,V 110%,V 110%, mean Protocol Target Dose Criteria PTV V 100% 95% V 108% 3% D 95 95% D 99 93% Body V 110% 0% NRG HN001 Plan in DICOM RT Dose-Volume Analysis Review V 100%, D 0.03cc D 50,D 02, D 98 PTV V 100% =95% 90% D 99 90% 85% D.03cc 115% 120% NRG HN002 Plan in DICOM RT Dose-Volume Analysis Review V 100%, D 0.03cc,D 95%,D 99, D 0.03cc, PTV D 95=100% 105% D 99 93% 90% D.03cc 110% 115% Guidelines are not Always Followed Absorbed dose is not specified to a volume We don t see Rx=D v Dose bounds are placed on D 95 but not D 50 Homogeneity Index is not reported Maximum dose is determined as D abs vol. Mininum dose is determined as D 99 Reporting misses D 50 Why should the MD care? Why should there be guidelines? Why ICRU? 5

6 Why a Guideline? Absent a Prescription Rule, The Dose Plan is Undetermined under Competing Aims PTV D 95 95%Rx D.03cc 107% Rx V % Rx 1.08 Rx 1.0 Rx D 95 95%Rx D.03cc 107% Rx V % Rx D 95 = 100% Rx D.03cc = 108% Rx 1.08 Rx 95% 1.0 Rx D 95 95% Rx D.03cc 107% Rx 6

7 D 95 = 99% Rx D.03cc = 107% Rx 1.07 Rx.99 Rx 95% D 95 95% Rx D.03cc 107% Rx D 95 = 95% Rx D.03cc = 103% Rx 1.03 Rx 95%.95 Rx D 95 95% Rx D.03cc 107% Rx MD Directive X Dose Distribution Published Guideline X Dose Distribution It is strongly recommended that if the method of prescription in a protocol or treatment aim is changed from a point-dose to a dose-volume approach, the impact on the absorbed dose received by patients should be determined. 7

8 D 98 D 50 is close to ICRU reference points dose D 50% =60 Gy D 98% =60 Gy V 100 = 95% 90% D 99 =90-85% D.03cc %Rx 1.21 Rx 1.0 Rx V 100 = 95% Rx D.03cc = 121% Rx D 99 = 92% Rx 95%.92 Rx V 100 = 95% 90% D.03cc %Rx D 99 =90-85% 1.15 Rx 1.0 Rx 91%.95 Rx.87 Rx V 100 = 91% Rx D.03cc = 115% Rx D 99 = 87% Rx 8

9 V 100 = 95% 90% D.03cc %Rx D 99 =90-85% 1.19 Rx 1.0 Rx.98 Rx 93%.90 Rx V 100 = 93% Rx D.03cc = 119% Rx D 99 = 90% Rx Standardization Fosters Outcome Comparisons by Reducing Noise Population Agent Rx D 95 Rx D 50 Total A = B = C = D = E = Proportion of Cures in Sample Rx D 95 Rx D 50 All A B C D E

10 Actual Cures Agent Rx D 95 Rx D 50 Total A B C D E Observed Cures Agent Cures Not Cures A B C D E Probability if Independent by Chi Square= Population Observed Cures Agent Rx D 95 Rx D 50 Rx PTV Rx D 50 A B C D E Probability if Independent by Chi Square =

11 Population Actual Cures Agent Rx D 95 Rx D 50 Rx PTV Rx D 50 A B C D E Probability if Independent by Chi Square= Why? From, taken from Das, I (2008) D 95 =100% D 02 =110% Rx D 95 is easily manipulated OAR 1.15 Rx 1.0 Rx D 95 =100% D 02 =115% Rx 1.04 Rx 11

12 D 95 =100% D 02 =110% Rx OAR 1.10 Rx D 95 =100% D02 =110% Rx 1.0 Rx 0.96 Rx Das I. et al Practical Radiation Oncology (2017) 7, e145-e155 D/ V is small near D 50 The greatest slope for the cumulative DVH is at or close to the median absorbed dose D50 Why Report D 50 Without D 50 we lack information on dose given to the majority of the tumor You can t cure the tumor if you don t hit it Looking at min and max point doses discounts error in calculation and boundary position of the tumor 12

13 How to get back on track Specify a prescription value relative to D v = D v Plan to reach D v under the constraint bounds Demand proof if D v infeasible Use D v = D 50 If D 50 taken as mean, the formulation of the objective is not combinatorial. List all critical values in treatment guidelines Next Generation of Treatment Guidelines Training that is Hype, Hyper or Loopy 13