IMRT and 3D CRT in cervical Cancers
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Transcript of IMRT and 3D CRT in cervical Cancers
Slide 1
3D CRT and IMRT in Cervical CancersDepartment of RadiotherapyPGIMERChandigarh
Conformal Radiotherapy
Conformal radiotherapy (CFRT) is a technique that aims to exploit the potential biological improvements consequent on better spatial localization of the high-dose irradiation volume
- S. Webb
in Intensity Modulated Radiotherapy
IOP
Problems in conformation
Nature of the photon beam is the biggest impediment
Has an entrance dose.
Has an exit dose.
Follows the inverse square law.
Types of CFRT
Two broad subtypes :
Techniques aiming to employ geometric eldshaping alone
Techniques to modulate the intensity of uence across the geometrically-shaped eld (IMRT)
Modulation : Intensity or Fluence ?
Intensity Modulation is a misnomer The actual term is Fluence
Fluence referes to the number of particles incident on an unit area (m-2)
How to modulate intensity
Cast metal compensator
Jaw defined static fields
Multiple-static MLC-shaped elds
Dynamic MLC techniques (DMLC) including modulated arc therapy (IMAT)
Binary MLCs - NOMOS MIMiC and in tomotherapy
Robot delivered IMRT
Scanning attenuating bar
Swept pencils of radiation (Race Track Microtron - Scanditronix)
Comparision
MLC based IMRT
Step & Shoot IMRT
IntesntiyDistanceSince beam is interrupted between movements leakage radiation is less.
Easier to deliver and plan.
More time consuming
Effecient delivery requires fast beam cycling dark current in tube can cause unwanted radiation during movement.
Dynamic IMRT
Faster than Static IMRT
Smooth intensity modulation acheived
Beam remains on throughout leakage radiation increased
More susceptible to tumor motion related errors.
Additional QA required for MLC motion accuracy.
IntesntiyDistance
Potential of Conformal RT
For Whole Pelvic Treatments:
Reduction in acute small bowel morbidity.
Reduction in acute hematological toxicity with bone marrow sparing.
Prevention of late term anorectal/ GI and GU dysfunction.
Escalation of dose to the pelvic lymphnodes.
Better matching of dose profiles in simultaneous treatments.
For simultaneous extended field irradiation ( CCT).
Better target coverage with modern day improvements in conjunction with image based brachytherapy
As an alternative to brachytherapy:
In distorted anatomy to circumvent limitations of brachytherapy.
To give higher dose to pelvic nodes present at time of brachyRx.
In postoperative patients with residual central disease instead of intersitial brachytherapy.
Caveats: Conformal Therapy
Significantly increased expenditure:
Machine with treatment capability
Imaging equipment: Planning and Verification
Software and Computer hardware
Extensive physics manpower and time required.
Conformal nature highly susceptible to motion and setup related errors Achilles heel of CFRT
Target delineation remains problematic.
Radiobiological disadvantage:
Decreased dose-rate to the tumor
Increased integral dose (Cyberknife > Tomotherapy > IMRT)
Conformal Radiation Planning
Initial Steps
Clinical Examination to note down tumor extent:
Vaginal mucosal extension is best appreciated on clinical examination
Preplanning steps:
Oral Contrast
Rectal Contrast
Cervical markers
Patient Preperation
Positioning and Immobilization
Two of the most important aspects of conformal radiation therapy.
Basis for the precision in conformal RT
Needs to be:
Comfortable
Reproducible
Minimal beam attenuating
Affordable
Several types of immobilization options available for cervical cancers
Types of Immobilization
Immoblization devicesFrame basedFramelessInvasiveNoninvasive
Usually based on a combination of heat deformable casts of the part to be immobilized attached to a baseplate that can be reproducibly attached with the treatment couch.
The elegant term is Indexing
Thermoplastics
Immobilization options
Thermoplastics form the basis for immobilzation in head and neck
In the pelvis these are difficult to be used as:
Lack of bony points for fixation for rigid devices.
Continuing abdominal movements with respiration
Presence of fat pads and folds
Therefore other techniques needed for immobilization.
In PGI we use simple supine positioning with skin markings:
Cheap
Reproducible
Ease of use and comfortable for patient.
Patient Positioning
Our Method
Immobilization: Other methods
Elekta Body FrameBody Fix system A third system (BodyFIX, Medical Intelligence) has been evaluated by Fuss et al. (2004). It consists of a base plate with variable sizes of a vacuum cushions and a clear plastic foil covering the patients body. The cushion is modeled using an additional vacuum between the patients front and a plastic foil. An arch-like attachment can be afxed to the base plate providing CT-, MR-, and PET-visible ducials.
Accuracy of systems
With the precision of the body fix frame the target volume will be underdosed (< 90% of prescribed dose) 14% of the time!!!
CT simulator
70 85 cm bore
Scanning Field of View (SFOV) 48 cm 60 cm Allows wider separation to be imaged.
Multi slice capacity:
Speed up acquistion times
Reduce motion and breathing artifacts
Allow thinner slices to be taken better DRR and CT resolution
Allows gating capabilities
Flat couch top simulate treatment table
MRI
Superior soft tissue resolution
Ability to assess neural and marrow infiltration
Ability to obtain images in any plane - coronal/saggital/axial
Imaging of metabolic activity through MR Spectroscopy
Imaging of tumor vasculature and blood supply using a new technique dynamic contrast enhanced MRI
No radiation exposure to patient or personnel
Importance of MRI
Dimopoulos JC, Schard G, Berger D, Lang S, Goldner G, Helbich T, et al. Systematic evaluation of MRI findings in different stages of treatment of cervical cancer: Potential of MRI on delineation of target, pathoanatomic structures, and organs at risk. International Journal of Radiation Oncology*Biology*Physics. 2006 Apr 1;64(5):1380-1388.
PET: Principle
Unlike other imaging can biologically characterize a leison
Relies on detection of photons liberated by annhilation reaction of positron with electron
Photons are liberated at 180 angle and simultaneously detection of this pair and subsequent mapping of the event of origin allows spatial localization
The detectors are arranged in an circular array around the patient
PET- CT scanners integrate both imaging modalities
PET-CT scanner
Flat couch top insertCT ScannerPET scanner
60 cmAllows hardware based registration as the patient is scanned in the treatment position
CT images can be used to provide attenuation correction factors for the PET scan image reducing scanning time by upto 40%
Markers for PET Scans
Metabolic marker
2- 18Fluoro 2- Deoxy Glucose
Proliferation markers
Radiolabelled thymidine: 18F Fluorothymidine
Radiolabelled amino acids:11C Methyl methionine, 11C Tyrosine
Hypoxia markers
60Cu-diacetyl-bis(N-4-methylthiosemicarbazone) (60Cu-ATSM)
Apoptosis markers
99mTechnicium Annexin V
PET FiducialsRadiolabelled Thymidine based markers are based on the principle that they can be used to detect proliferation of cells as onlu actively divinding cells take up thymidine.The use of these markers can thus allow the oncologist to obtain a rough idea of the proliferation markers.
The use of cell proliferation markers namely amino acids provides us with the advantage that the inflammatory cells take up less of the substance and so it is possible to image the tumor bearing tissues seperately.
Hypoxia markers are substances that contain a nitroimidazole entity which is reduced and subsequently the entire molecule is taken up by the concerned cell. It acts as a hypoxia marker in such circumstances.
Among all the hypoxic cell markers the Cu-ASTM is the best as:
The images are produced within 10 min of contrast injection.
Images have high contrast with moderate doses.
The substance is taken up by cells with active mitochondria and thus it is possible to distinguish alive cells from necrotic ones.
Apoptosis markers are based on certain molecules that avidly bind to domains of membrane lipids that are exposed on apoptotic cells, Annexin V is an example of such a molecule and it binds to the membrane bound phosphatidyl serine which is exposed on the outer leaflet of cell membrane on cell death.
Image Registration
Technique by which the coordinates of identical points in two imaging data sets are determined and a set of transformations determined to map the coordinates of one image to another
Uses of Image registration:
Study Organ Motion (4 D CT)
Assess Tumor extent (PET / MRI fusion)
Assess Changes in organ and tumor volumes over time (Adaptive RT)
Types of Transformations:
Rigid Translations and Rotations
Deformable For motion studies
Concept
Image Registration
The algorithm first measures the degree of mismatch between identical points in two images (metric).
The algorithm then determines a set of transformations that minimize this metric.
Optimization of this transformations with multiple iterations take place
After the transformation the images are fused - a display which contains relevant information from both images.
Image Registration
The registration metrics used are of two broad types:
Geometry based metrics: This metric type finds the difference between two images based on several points or surface of a structure(s) in question
Intensity based metrics: This type of metric attempts to evaluate the difference in the two images by using numerical grey scale differences.
The geometry based metrics are limited by the ability to precisely determine the location of identical points or delineate the surface of the organ in question in two image sets. This is allright in certain structures like the brain. However the different levels of imaging contrast provided by different studies makes the use of this process difficult in practice in other areas
The intensity based metrics on the other hand determine the differnce in the intensity distribution of voxels and calculate the degree of transformations required.
Various types of intensity based metrices exist:
Sum of squared differences
Cross correlation metric
Mutual information metric
The mutual information technique is most commonly used to estimate the differnce in the intensity of voxel values. The technique's strength lies in the fact that it can overcome differences due to areas of different contrasts in the two images and in addition it can overcome the problem due to missing data.
Target Volume delineation
The most important and most error prone step in radiotherapy.
Also called Image Segmentation
The target volume is of following types:
GTV (Gross Tumor Volume)
CTV (Clinical Target Volume)
ITV (Internal Target Volume)
PTV (Planning Target Volume)
Other volumes:
Targeted Volume
Irradiated Volume
Biological Volume
Target Volumes
GTV: Macroscopic extent of the tumor as defined by radiological and clinical investigations.
CTV: The GTV together with the surrounding microscopic extension of the tumor constitutes the CTV. The CTV also includes the tumor bed of a R0 resection (no residual).
ITV (ICRU 62): The ITV encompasses the GTV/CTV with an additional margin to account for physiological movement of the tumor or organs. It is defined with respect to a internal reference most commonly rigid bony skeleton.
PTV: A margin given to above to account for uncertainities in patient setup and beam adjustment.
Definitions: ICRU 50/62
GTVCTVITVPTV
TV
IV
Treated Volume: Volume of the tumor and surrounding normal tissue that is included in the isodose surface representing the irradiation dose proposed for the treatment (V95).
Irradiated Volume: Volume included in an isodose surface with a possible biological impact on the normal tissue encompassed in this volume. Choice of isodose depends on the biological end point in mind.
Organ at Risk (ICRU 62)
Normal critical structures whose radiation sensitivity may significantly influence treatment planning and/or prescribed dose.
A planning organ at risk volume (PORV) is added to the contoured organs at risk to account for the same uncertainities in patient setup and treatment as well as organ motion that are used in the delineation of the PTV.
Each organ is made up of a functional subunit (FSU)
Organs can be classified into 4 broad types based on the arrangement of the FSUs:
Serial: Where the FSUs are arranged in serial and damage to one can result in the total impairment of function of the organ. Example: Spinal cord
Parallel: Here the FSU are arranged in parallel so that damage to a certain proportion of the FSUs are required befor e functional deterioration becomes apparent. Example Parotid Gland, Lung and Kidney
Serial in parallel: These organs have serially arranged FSU so that damage to a single FSU can impair the function significantly but damage to a certain proportion is still required before the damage becomes apparent. Example: Heart.
Combination of serial and parallel organs: Here the damage to the serial component can result in the stoppage of function of the organ concerned. Example is the nephron
The concept of the organization of the FSUs has lead to a new classification of organs for purposes of calculation of the equivalent dose. Organs are now classified into 3 categories:
Critical Element(CE): Example Spinal Cord
Critical Volume (CV): Example Lung
Graded Response (GR): Example oral mucosa
CTV Delineation
The CTV to be delineated for cervical cancers consists of three components (if patient is treated with RT CT alone)
Low Risk CTV: Consists volume at risk of potential microscopic disease spread at the time of diagnosis. Typically treated to a dose of 45 -50 Gy.
Intermediate Risk CTV: Major risk of local recurrence in areas that correspond to initial macroscopic extent of disease. The intent is to deliver a total radiation dose appropriate to cure signicant microscopic disease in cervix cancer, which corresponds to a dose of at least 60 Gy.
High Risk CTV: Major risk of local recurrence because of residual macroscopic disease. The intent is to deliver a total dose as high as possible (85 - 90 Gy) and appropriate to eradicate all residual macroscopic tumour.
CTV Parametrium
Ventral: Bladder
Dorsal: Perirectal fascia
Medial: Tumor/cervical rim,
Lateral: Pelvic wall (PW)
At the PW, the space that contains vessels and lymph nodes is particularly important.
Nodal Anatomy
Superficial common iliac 24%Deep Common iliac 20%Internal Iliac 12%External Ilac 24%Superficial Obturator 92%Deep Obturator 8%Presacral - 8%
Delineation of Nodal Volume
Common Iliac Nodes:7 mm margin around vessels. Extend posterior and lateral borders to psoas and vertebral bodyTaylor A, Rockall A, Powell M. An Atlas of the Pelvic Lymph Node Regions to Aid Radiotherapy Target Volume Definition. Clinical Oncology. 2007 Sep ;19(7):542-550.
Delineation of Nodal Volume
External iliac Nodes:7 mm margin around vessels. Extend anterior border by a further 10 mm anterolaterally along the iliopsoas muscle to include the lateral external iliac nodesInternal iliac Nodes:7 mm margin around vessels. Extend lateral borders to pelvic side wallTaylor A, Rockall A, Powell M. An Atlas of the Pelvic Lymph Node Regions to Aid Radiotherapy Target Volume Definition. Clinical Oncology. 2007 Sep ;19(7):542-550.
Delineation of Nodal Volume
Presacral Nodes:Subaortic: 10 mm strip over anterior sacrum; Mesorectal: cover entire mesorectal spaceTaylor A, Rockall A, Powell M. An Atlas of the Pelvic Lymph Node Regions to Aid Radiotherapy Target Volume Definition. Clinical Oncology. 2007 Sep ;19(7):542-550.
Delineation of Nodal Volume
Taylor A, Rockall A, Powell M. An Atlas of the Pelvic Lymph Node Regions to Aid Radiotherapy Target Volume Definition. Clinical Oncology. 2007 Sep ;19(7):542-550.
Delineation of Nodal Volume
Taylor A, Rockall A, Powell M. An Atlas of the Pelvic Lymph Node Regions to Aid Radiotherapy Target Volume Definition. Clinical Oncology. 2007 Sep ;19(7):542-550.Obturator Nodes:Join external and internal iliac regions with a 17 mm wide strip along the pelvic side wall
Delineation of Nodal Volume
Taylor A, Rockall A, Powell M. An Atlas of the Pelvic Lymph Node Regions to Aid Radiotherapy Target Volume Definition. Clinical Oncology. 2007 Sep ;19(7):542-550.
Extent of Nodes Covered
Taylor et al have advocated the use of a 7 mm margin around the blood vessels unlike Chao's recommendations as it was seen that educing margins to 7 mm from 10 mm could result in 20 -30% reduction in the volume of normal tissues included in the PTV.
PTV Delineation
The exact PTV depends on:
Setup inaccuracies
Organ motion
The extent of setup inaccuracies will differ from institution to instituiton
In PGI we use the following margins:
1 cm cranio-caudal direction
0.7 cm lateral
0.7 cm antero posterior
Interfraction Motion: ITV
Uterus:
SI: 7 mm
AP : 4 mm
Cervix:
SI: 4 mm
Rectum:
Diameter: 3 46 mm
Volumes: 20 40%
In many studies decrease in volume found during treatment
Bladder:
Max transverse diameter mean 15 mm variation
SI displacement 15 mm
Volume variation 20% - 50%
Langen, K. M., & Jones, D. T. (2001). Organ motion and its management. International journal of radiation oncology, biology, physics, 50(1), 265-78.
Planning workflow
Define a dose objectiveTotal DoseTotal Time of delivery of doseTotal number of fractions
Choose Number of BeamsChoose beam angles and couch angles
Organ at risk dose levels
Choose Planning Technique
Forward PlanningInverse Planning
Forward Planning
A technique where the planner will try a variety of combinations of beam angles, couch angles, beam weights and beam modifying devices (e.g. wedges) to find a optimum dose distribution.
Iterations are done manually till the optimum solution is reached.
Choice for some situations:
Small number of fields: 4 or less.
Convex dose distribution required.
Conventional dose distribution desired.
Conformity of high dose region is a less important concern.
Planning Beam orientation
Beams Eye View DisplayRoom's Eye ViewDigital Composite RadiographBEV Display: The observers viewing point is at the source of radiation looking out along the axis of the radiation beam.
Allows planner to visualize target volumes and critcal organ volumes facilitating planning of the aperture.
REV Display: The planner can simulate any arbitrary viewing location within the treatment room.
Allows planner to appreciate the composite beam arrangement and geometry
Digitally Composite Radiograph is a type of DRR that allows different ranges of CT numbers that relate to a certain tissue type to be selectively suppressed or enhanced in the image.
Analogous to a transmission radiograph through a virtual patient where certain tissue types have been removed, leaving only the organs of interest to be displayed.
Allow better visualization of the organ of interest
Beam Arrangement
Inverse Planning
1. Dose distribution specified
Forward Planning
2. Intensity map created3. Beam Fluence modulated to recreate intensity map
Inverse Planning
Spatial dose distribution in the 3 dimensional volume is first defined.
Defination of dose coverage for the PTV(s)
Defination of sparing for the organ at risk
Establishment of a hierarchy of targets and organs at risk
Beam intensity distribution required to achieve this dose distribution goal would be calculated.
Photon Fluence required to deliver this intensity distribution is then generated.
Optimization
Refers to the technique of finding the best physical and technically possible treatment plan to fulfill the specified physical and clinical criteria.
A mathematical technique that aims to maximize (or minimize) a score under certain constraints.
It is one of the most commonly used techniques for inverse planning.
Variables that may be optimized:
Intensity maps
Number of beams
Number of intensity levels
Beam angles
Beam energy
Optimization Criteria
Refers to the constraints that need to be fulfilled during the planning process
Types:
Physical Optimization Criteria: Based on physical dose coverage
Biological Optimization Criteria: Based on TCP and NTCP calculation
A total objective function (score) is then derived from these criteria.
Priorities are defined to tell the algorithm the relative importance of the different planning objectives (penalties)
The algorithm attempts to maximize the score based on the criteria and penalties.
Normal Organ Constraints
As per data given by Perez et al:
Gr III rectosigmoid complications:
1-4% with dose < 80 Gy
9% with dose 80 Gy
Moderate Urinary sequale:
2% < 70 Gy
5% 75 Gy
Grade III small bowel sequale:
1% 50 Gy
2% to 4% > 60 Gy
RectumBladderPerez CA, Grigsby PW, Lockett MA, Chao KSC, Williamson J. Radiation therapy morbidity in carcinoma of the uterine cervix: dosimetric and clinical correlation. International Journal of Radiation Oncology*Biology*Physics. 1999 Jul 1;44(4):855-866.
Normal Organ Constraints
Mundt AJ, Lujan AE, Rotmensch J, Waggoner SE, Yamada SD, Fleming G, et al. Intensity-modulated whole pelvic radiotherapy in women with gynecologic malignancies . International Journal of Radiation Oncology*Biology*Physics. 2002 Apr 1;52(5):1330-1337.
Small Intestine: DVH correlates
Acute GI toxicity correlates with small bowel dose
% volume of small intestine receiving doses in the range of 75 -100% of prescribed dose significant predictor.
In a study of 50 patients Volume of small bowel receiving 100% of prescribed dose retained significance in multivariate analysis.
1. Roeske JC, Lujan AE, Krishnamachari U, Mundt AJ. Dose-volume histogram analysis of acute gastrointestinal toxicity for gynecologic patients receiving intensity-modulated whole pelvic radiotherapy. International Journal of Radiation Oncology*Biology*Physics. 2001 Nov 1;51(3, Supplement 1):221-222.
2. Roeske JC, Bonta D, Mell LK, Lujan AE, Mundt AJ. A dosimetric analysis of acute gastrointestinal toxicity in women receiving intensity-modulated whole-pelvic radiation therapy. Radiotherapy and Oncology. 2003 Nov ;69(2):201-207.
Colorectum: DVH Correlates
Anal Canal Dysfunction:
Correlated with radiation doses in the range from 50 to 60 Gy.
Rectal Dysfunction:
Risk of late rectal bleeding significantly high when the rectum is enclosed by the 50 -60 Gy isodose curve for more than 1 cm length
Fokdal L, Honor H, Hyer M, Maase H. Dose-volume Histograms Associated to Long-term Colorectal Functions in Patients Receiving Pelvic Radiotherapy. Radiother Oncol. 2005 ;74(2):203-10.
Bone Marrow: DVH correlates
Significant correlation of volume of bone marrow receiving doses of >10 Gy
1. Mell LK, Kochanski JD, Roeske JC, Haslam JJ, Mehta N, Yamada SD, et al. Dosimetric predictors of acute hematologic toxicity in cervical cancer patients treated with concurrent cisplatin and intensity-modulated pelvic radiotherapy. International Journal of Radiation Oncology*Biology*Physics. 2006 Dec 1;66(5):1356-1365.
Optimization
Plan Evaluation: Cumulative DVH
Cumulative DVHs give a quick overview of the 3D Dose distribution.
Analysis of a absolute volume vs absolute dose histogram is more intuitive.
Always look for the absolute volume incorporated in the dose limit.
Also look for the tail of the curve and look what is the dose there.
Plan Evaluation: Differntial DVH
Differential DVH allow a visual representation of the dose homogenity in the target volume.
Ideally the DVH should have a sharp peak in the differential DVH
The peak of the curve gives a good representation of the modal dose being received by the volume in question.
Plan Evaluation: Color Wash
The color wash and it's counterpart the isodose views allow quick visual verification of the dose distribution.
Coverage of the PTV should be assessed with the color wash or isodose curve display on each slice
Oragan doses should also be evaluated for the clinically relevant dose limit set.
Verification
Both absolute and relative dosimetric verification is essential for each IMRT plan.
Absolute dose variations should be 3%.
Should be measured in a region of low dose gradient.
Relative dose variation 5% is acceptable.
Clinical Results
Dosimetric Comparisions
Selvaraj et al compared IMRT and conventional 3D CRT plans for cervical cancer patients using 7 field IMRT.
1. Selvaraj RN, Gerszten K, King GC, Sonnik D, Heron DE. Conventional 3-D versus intensity modulated radiotherapy for the adjuvant treatment of gynecologic malignancies: a comparative study of dose-volume histograms and the potential impact on toxicities. International Journal of Radiation Oncology*Biology*Physics. 2001 Nov 1;51(3, Supplement 1):218-219.
WPIMRT: Clinical Results
Chen M, Tseng C, Tseng C, Kuo Y, Yu C, Chen W. Clinical outcome in posthysterectomy cervical cancer patients treated with concurrent Cisplatin and intensity-modulated pelvic radiotherapy: comparison with conventional radiotherapy. International journal of radiation oncology, biology, physics. 2007 Apr 1;67(5):1438-44
Mundt AJ, Roeske JC, Lujan AE, Yamada SD, Waggoner SE, Fleming G, et al. Initial Clinical Experience with Intensity-Modulated Whole-Pelvis Radiation Therapy in Women with Gynecologic Malignancies, . Gynecologic Oncology. 2001 Sep ;82(3):456-463.
Mundt AJ, Lujan AE, Rotmensch J, Waggoner SE, Yamada SD, Fleming G, et al. Intensity-modulated whole pelvic radiotherapy in women with gynecologic malignancies . International Journal of Radiation Oncology*Biology*Physics. 2002 Apr 1;52(5):1330-1337.
Kochanski J, Mehta N, Mell L, Roeske J, Sutton H, Mundt A. Outcome of Cervical Cancer Patients Treated with Intensity Modulated Radiation Therapy. International Journal of Radiation Oncology*Biology*Physics. 2005 Oct 1;63(Supplement 1):S214.
.
WPIMRT: Chronic Toxicity
Mundt et al reported a detailed comparision of IMRT vs 3DCRT
WPIMRT reduced chronic GI toxicity to 11% from 50% in conventional 3D CRT.
Significant difference on multivariate analysis
Majority of patients of WPIMRT who had GI toxicity had grade I toxicity only.
Mundt AJ, Mell LK, Roeske JC. Preliminary analysis of chronic gastrointestinal toxicity in gynecology patients treated with intensity-modulated whole pelvic radiation therapy. International Journal of Radiation Oncology*Biology*Physics. 2003 Aug 1;56(5):1354-1360.
IMRT: Extended Pelvic Radiation
RTOG 92-10:
31% acute Grade 3 - 4 nonhematologic toxicity
76% acute Grade 3 - 4 chemotherapy related toxicity
31% of patients did not complete radiotherapy
Salama et al (University of Illinois):
13 patients with various pelvic malignancies (11 mo followup)
Only 2 / 13 patients had Grade III acute toxicity
Late Gr III toxicity:
Small bowel obstruction:1
Lymphedema: 1
Salama JK, Mundt AJ, Roeske J, Mehta N. Preliminary outcome and toxicity report of extended-field, intensity-modulated radiation therapy for gynecologic malignancies. International Journal of Radiation Oncology*Biology*Physics. 2006 Jul 15;65(4):1170-1176.
IMRT: Extended Pelvic RT
Beriwal et al (University of Pittsburg):
36 patients with Stage IB2IVA cervical cancer
Para-aortic nodes to the superior border of L1 treated
Weekly Cisplatin CCT
Gr III late toxicity: 10%
2yr LRC: 80%
2yr DFS: 51%
Beriwal S, Gan GN, Heron DE, Selvaraj RN, Kim H, Lalonde R, et al. Early Clinical Outcome With Concurrent Chemotherapy and Extended-Field, Intensity-Modulated Radiotherapy for Cervical Cancer. International Journal of Radiation Oncology*Biology*Physics. 2007 May 1;68(1):166-171.
Bone Marrow Sparing
Dosimetric comparision of bone marrow sparing IMRT (Lujan et al):
Found that between a dose level of 18 20 Gy a significant reduction in volume of bone marrow irradiated was obtained with IMRT.
Brixey and Colleagues specifically compared hematological toxicity of WP-IMRT vs WPRT in the setting of concurrent CCT
Brixey CJ, Roeske JC, Lujan AE, Yamada SD, Rotmensch J, Mundt AJ. Impact of intensity-modulated radiotherapy on acute hematologic toxicity in women with gynecologic malignancies. International Journal of Radiation Oncology*Biology*Physics. 2002 Dec 1;54(5):1388-1396.
Conclusions
Both 3D CRT and IMRT are still investigational tools.
However unless dose escalation is done no significant improvement in the control rates should be expected.
Chronic and acute toxicity amelioration are the more relevant endpoints.
Also may allow tighter integration of brachy therapy/ chemotherpay / biological therapy
Biologically optimized radiotherapy is an exciting new development
Real impact can only be realised with meticulous care in planning and execution.
Thank You
Dr Santam Chakraborty Department of Radiotherapy, PGIMER Chandigarh
SystemTechniqeXYZStereotactic Body FrameNon invasive, vacccum based5-7 mm1 cmHeidelberg frameNon invasive, vaccum based5 mm10 mmBody Fix FrameNon invasive, Vacccum based with plastic foil0.4 3.9 mm0.1 1.6 mm0.3 3.6 mm
???Page ??? (???)11/05/2007, 23:46:34Page / ??????Page Page AuthorYear NCCT DoseResultMundt (P,NR)200336Y (53%)45 Gy (1.8 Gy/#)80% stage I-II; PTV S3 to L4/5 interspace; Chronic GI toxicity 15% (n= 3; 1 Gr II, 2 Gr I); 50% incidence in Conventional Mundt (P,NR)200240Y45 Gy (1.8 Gy/#)60% Acute Gr II toxicity (90% Gr II in Conv.); Less GU toxicity (10% vs 20%); Patients not requiring antidiarrheal halved!Chen (P,NR)200733Y50.4 Gy / 28# All Stage I -II; All Post Hysterectomy; 1 yr LRC 93%; Acute GI toxicity 36% (Gr I-II); Acute Gu toxicity 30% (Gr I-II). Chronic GI toxicity 6% (34% in 3D CRT).Kochanski200562Y (64%)45 Gy (1.8 Gy /#)29% Post op; 20 Stage IIB-IIIB; 3 yr DFS 72.7%; 3 yr pelvic control 87.5%; 5% Gr II or higher late toxicity
???Page ??? (???)11/05/2007, 23:46:34Page / ??????Page Page