Potential role of Image Guided Radiotherapy in locally advanced Cancer Cervix. Dr.Vikas Roshan MD, ECMO, CCEPS, PDCR. IGRT Fellow NUCI-NUS Singapore. Clinical Fellow NCCHE, Japan. Consultant Radiation Oncology, SMVDNSH.
SMVDNSH 2016-2017 n=240 Cancer Types in SMVDNSH Department of Radiation Oncology,2017
SMVDNSH DATA • Total no of patients 44 • Age range 32-84 years • Stage I-1(2%), STAGE II-3 (6%), STAGE 3- 36 (81%), Stage IVA-04 (9%) • Radiation dose 50.4 Gy/28# followed by ICRT X3# • VMAT 100 % • Radical CRT 39 (88%) patients • POCRT 3 (6%) • PALL RT 2 (5%)
No grade II,III,IV GU toxicity • Two years follow up, 4 (9%) patients devloped distant recurence.Late toxicity rectal bleed grade 2, 2 patients.(4.5%) • DVT total 3 patients,one diagnosed during treatment. • RT Interruption nil and tolerated well • No Skin Toxicity • One patient died after disseminated disease. • 40 patients on follow up without clinically evident disease.
IGRT Definition • Radiation therapy that employs imaging to maximize accuracy and precision throughout its entire process. ACR-ASTRO practice parameter 2014
IGRT Concepts ICRU 50 ICRU 29 ICRU 62
Key objectives Maximize dose to Tumour Avoid adjacent critical structures High quality efficient delivery
IGRT workflow X,Y,Z Table Correction Image display and registration on XVI WORKSTATION Comparison of target position with adaption of beam aperture MOSAIQ for on-line or off-line registration and stored in database XVI Image Acquisition And reconstruction Image export to TPS
Sources of uncertainties • Inter-fraction (between fractions) • Setup: weight loss, rotation, etc. • Organ movement Physiological filling/emptying(bladder/rectum/emptying) • Intra-fraction (during treatment) • Set up Discomfort/tension, uncontrolled movement. • Organ movement Lung, bowel gas, peristalsis ,etc.
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43 patients were evaluated Stage I-III • Pelvic arteries were contoured on non–contrast-enhanced CT simulation images of 43 • patients with cervix cancer, FIGO Stages I–III. Vessel contours were hidden, and conventional pelvic fields were • outlined: (1) anterior/posterior fields (AP): superior border, L5–S1 interspace; inferior border, obturator • foramina; lateral border, 2 centimeters lateral to pelvic brim. (2) Lateral fields (LAT): Anterior border, • symphysis pubis; posterior border, S2–S3 interspace. Distances were measured between the following: (1) • bifurcation of the common iliac artery and superior border, (2) external iliac artery and lateral border of the AP • field, and (3) external iliac artery and anterior border of the LAT field. The distances were considered as • “inadequate” if <15 mm, “adequate” if 15–20 mm, and “generous” if >20 mm.
KV Imaging 2D/2.5D • 2 or more planar images are acquired at orthogonal angles. • It allows measurement in three directions anterior-posterior/lateral/superior-inferior • 2D/2.5D IGRT with Mosaiq setup intelligence(orthogonal pair of images)
MVI EPI (I-ViewGT) • Standard feature in most Linear Accelerator • Contrast issue with bone , soft tissue and air can be poorly represented in MV-EPI.
3D Imaging • Volumetric imaging • Internal structures can be visualized • Cone beam CT/Megavoltage CT/CT on rails/Ultrasound • Cone Beam CT(CBCT) is a KV tube mounted at 90 degree to the linac head. • We can take both KV/MV imaging. • Precise registration of acquired CBCT/MVCT with reference CT • No need for surrogate markers • We can match the structures as defined in TPS • Large field of view.
New Generation of IGRT • 4D Cone Beam CT • MR guidance MRguidedRT/MRIdian/VIEWRAY
Correction • Real time tracking • Online (IGRT) Systematic and Random errors • Offline Systematic errors
Benefits of IGRT • Conformal distribution to Tumour and OARS • Dose escalation • Verification of Applicator Position • Normal Tissue Dosimetry
See better, plan better, deliver better • Opportunity to customize plan/treatment to patient anatomy(adaptive). • Tight conformance so confirm target first • High resolution images before treatment delivery • Unless you know the target position you can precisely miss it.