I MRT- - THE STATE OF THE THE STATE OF THE I MRT EVI DENCE EVI DENCE Bhadrasain Vikram, MD Bhadrasain Vikram, MD
COMPARI NG TREATMENTS COMPARI NG TREATMENTS I f I receive I MRT: I f I receive I MRT: Will I live longer? � Will I live longer? � Will I live better (not � Will I live better (not � suffer adverse effects)? suffer adverse effects)?
SUMMARY SUMMARY � The evidence that I MRT has helped The evidence that I MRT has helped � any cancer patient live either longer any cancer patient live either longer or with a better quality of life, in or with a better quality of life, in comparison to 3D- -CRT, is almost CRT, is almost comparison to 3D non- -existent. existent. non � Furthermore, there is substantial risk Furthermore, there is substantial risk � that tumor control may be worse that tumor control may be worse after I MRT because after I MRT because
� There are numerous practical There are numerous practical � difficulties in defining the size, difficulties in defining the size, shape and deformation of the shape and deformation of the clinical target volume clinical target volume � Hot and cold spots plague the Hot and cold spots plague the � treatment planning for I MRT, treatment planning for I MRT, and and � I rradiating with I MRT even a I rradiating with I MRT even a � stationary phantom accurately stationary phantom accurately has proven surprisingly difficult. has proven surprisingly difficult.
� The published randomized studies of The published randomized studies of � I MRT in breast cancer did not really I MRT in breast cancer did not really use I MRT (dose- -sculpting) sculpting) use I MRT (dose � They decreased dose heterogeneity They decreased dose heterogeneity � within the breast by techniques that did within the breast by techniques that did not rise to the level of I MRT, and had not rise to the level of I MRT, and had been available and already in use in been available and already in use in many radiotherapy centers for decades. many radiotherapy centers for decades. � The published randomized studies of The published randomized studies of � I MRT in NPC showed rather modest I MRT in NPC showed rather modest benefit from the patient's benefit from the patient's perspective after parotid after parotid- -avoidance. avoidance. perspective
Answers: Answers: Question: Question: � We don We don’ ’t yet t yet � � Will I live Will I live � know! know! longer? longer? � I t is possible I t is possible � that you may that you may do worse. do worse.
Answers: Answers: Question: Question: � We don We don’ ’t yet t yet � � Will I live Will I live � know! know! better? better? � I t is possible I t is possible � that you may that you may do worse. do worse.
How could patients � How could patients � do WORSE after do WORSE after I MRT than I MRT than ‘Conventional Conventional’ ’ RT? RT? ‘
‘MI SADMI NI STRATI ONS MI SADMI NI STRATI ONS’ ’ WI TH WI TH ‘ I MRT I MRT � Discrepancies between prescribed Discrepancies between prescribed � dose and planned dose. dose and planned dose. � Discrepancies between planned dose Discrepancies between planned dose � and dose delivered ‘ ‘to an ideal to an ideal and dose delivered patient’ ’. . patient � Discrepancies between planned dose Discrepancies between planned dose � and dose delivered to an actual and dose delivered to an actual patient. patient.
� Discrepancies between Discrepancies between � prescribed dose and planned prescribed dose and planned dose. dose.
I MRT: PRESCRI BED vs. PLANNED I MRT: PRESCRI BED vs. PLANNED DOSE DOSE Das I . JNCI , 100:300- -7, 2008 7, 2008 Das I . JNCI , 100:300 � Studied 803 patients at five Studied 803 patients at five � institutions. institutions. � Treatment plans were done Treatment plans were done � by experienced physicists by experienced physicists (> 50 I MRT cases each). (> 50 I MRT cases each).
I MRT: PRESCRI BED vs. PLANNED I MRT: PRESCRI BED vs. PLANNED DOSE DOSE Das I . JNCI , 100:300- -7, 2008 7, 2008 Das I . JNCI , 100:300 RESULTS: RESULTS: � I n 46% of patients the plan delivered to I n 46% of patients the plan delivered to � the CTV a maximum dose more than 10% the CTV a maximum dose more than 10% ‘hotter hotter’ ’ than prescribed by the MD (worst than prescribed by the MD (worst ‘ case: 40% higher). case: 40% higher). � I n 63% of patients the plan delivered to I n 63% of patients the plan delivered to � the CTV a minimum dose more than 10% the CTV a minimum dose more than 10% ‘colder colder’ ’ than prescribed (worst case: than prescribed (worst case: ‘ 100% lower = zero). 100% lower = zero).
� Discrepancies between prescribed Discrepancies between prescribed � dose and planned dose. dose and planned dose. � Discrepancies between Discrepancies between � planned dose and dose planned dose and dose delivered ‘ ‘to an ideal patient to an ideal patient’ ’. . delivered � Discrepancies between planned dose Discrepancies between planned dose � and dose delivered to an actual and dose delivered to an actual patient. patient.
THE I DEAL PATI ENT THE I DEAL PATI ENT � We know the CTV precisely. We know the CTV precisely. � � There is absolutely no There is absolutely no � voluntary or involuntary voluntary or involuntary movement. movement. � There is absolutely no change There is absolutely no change � in the position, size or shape in the position, size or shape of the CTV or the OAR. of the CTV or the OAR.
I MRT: PLANNED vs. DELI VERED DOSE I MRT: PLANNED vs. DELI VERED DOSE I bbott GS. Technology in Cancer Research and Treatment, 5:481- -7, 2006. 7, 2006. I bbott GS. Technology in Cancer Research and Treatment, 5:481 � 128 RTOG member institutions imaged a 128 RTOG member institutions imaged a � phantom, developed a treatment plan, phantom, developed a treatment plan, then treated the phantom. then treated the phantom. � Goal: Goal: Deliver to the CTV a dose within 7% Deliver to the CTV a dose within 7% � of the planned dose. of the planned dose. � Results: Results: One One- -third of the institutions failed third of the institutions failed � the test (the dose delivered differed from (the dose delivered differed from the test the planned dose by up to 22% ; the high the planned dose by up to 22% ; the high dose region was off by up to 15 mm). dose region was off by up to 15 mm).
SOME REASONS FOR SOME REASONS FOR MI SADMI NI STRATI ONS MI SADMI NI STRATI ONS � I naccurate modeling by the TPS algorithm I naccurate modeling by the TPS algorithm � of field sizes formed by MLC leaves. of field sizes formed by MLC leaves. � I naccurate handling by the TPS of I naccurate handling by the TPS of � inhomogeneity corrections. corrections. inhomogeneity � Variable handling of cost Variable handling of cost- -function function � optimization by algorithms that can not be optimization by algorithms that can not be controlled by the user. controlled by the user. � I ncorrect data input into the TPS. I ncorrect data input into the TPS. � � I ndexing errors in the table movement I ndexing errors in the table movement � system. system. � I ncorrect monitor unit settings. I ncorrect monitor unit settings. � I naccurate positioning of the phantom (or � I naccurate positioning of the phantom (or � patient). patient).
SUMMARY SUMMARY � The evidence that I MRT has The evidence that I MRT has � helped any cancer patient live helped any cancer patient live either longer or with a better either longer or with a better quality of life, in comparison to quality of life, in comparison to 3D- -CRT, is almost non CRT, is almost non- -existent. existent. 3D � Furthermore, there is substantial Furthermore, there is substantial � risk that tumor control may be risk that tumor control may be worse after I MRT. worse after I MRT.
� Should we study I MRT? Should we study I MRT? � YES. � YES. � � Should we use it outside of Should we use it outside of � prospective trials? prospective trials? NO. � NO. �
‘ADVANCED ADVANCED’ ’ TECHNOLOGI ES TECHNOLOGI ES ‘ I MRT � I MRT � STEREOTACTI C � STEREOTACTI C � CYBERKNI FE � CYBERKNI FE � TOMOTHERAPY � TOMOTHERAPY � PROTONS � PROTONS � Etc., Etc. � Etc., Etc. �
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