• Radiation Oncology syn: RadioTherapy, is a branch of medicine that utilizes Ionizing Radiation of various types & energies to treat cancer & some benign conditions.
• With rapid technological advancements, the precision and accuracy has evolved rapidly to make RadioTherapy indispensable in the multi-modality management of cancer
• The propagation/transmission of energy from a Radiative Source to another medium is termed Radiation.
• Transmission of energy can be in the form of Electromagnetic waves or Particulate Radiation.
• Based on Energy, Radiation can be
• Ionizing (High Energy)
• Non-Ionizing (Low Energy)
1. Radio waves
4. Visible Light
Cellular effects of Radiation
• Ionizing Radiation injects energy into a material, like a microscopic bullet, until the radiation is stopped by the material due to absorption.
• On the cellular level, Radiation damages all molecules of the cell, but the ultimate target is the DNA, which will eventually kill the cell.
• Repair (of Sublethal Damage)
· Sublethal Radiation induced damage is repaired & helps Tumor cells (and normal tissue) recover.
· Both Tumor cells & Normal tissue cells proliferate & mitigate the effect of RT
· Hypoxic cells are resistant to radiation.
· Since a major part of the tumor is hypoxic, reductions in size after a fraction of Radiotherapy reoxygenates previously hypoxic cells, making them radiosensitive.
· Dividing cells are sensitive to RT in specific phases of the cell cycle
· As tumor cells are in different phases of the cell cycle, those in radiosensitive phase get killed first. Remaining cells continue the cycle and are killed at the next fraction of RT when they reach Radiosensitive phase.
• According to AIM
1. Curative syn. Definitive RT: Application of RT ALONE to achieve cure. e.g. Early Head & Neck, Early Cervix
2. Palliative RT: Application of RT to alleviate symptoms of Cancer. e.g. Bone metastases, Brain Metastases, Superior Vena Cava Obstruction
3. Prophylactic: Application of RT to prevent relapse in relapse-prone areas. e.g. Prophylactic Cranial Irradiation in Leukemias
• According to TIMING & combination with other modalities
1. Adjuvant RT: Application of RT after any kind of treatment modality. If given immediately after surgery, post-op RT
2. Neo-Adjuvant RT: Application of RT before any kind of treatment modality. If given immediately before surgery, pre-op RT
3. RadioChemotherapy syn. Concurrent ChemoRadiotherapy (CCRT): Application of RT concurrently with Chemotherapy. Can be Adjuvant or Neo-Adjuvant.
• According to MODE of delivery of Radiotherapy
• External Beam RadioTherapy: Given externally to the patient by a treatment machine e.g. Linear Accelerator
• Brachytherapy: Given by implanting Radioactive sources directly on patient (Interstitial) or in body cavities (Intracavitary).
• Intra-Operative RadioTherapy: Given directly to Tumor Bed at time of surgery.
• Stereotactic Radiotherapy/RadioSurgery: Given externally by utilizing a rigid frame to deliver high doses in few fractions, to critical sites (e.g. CNS tumors) using a special machine. e.g. Gammaknife
• According to PRECISION
• 2 Dimensional (Traditional) Radiotherapy: Obsolete. Minimal sparing of normal tissue
• 3 Dimensional Conformal Radiotherapy (3D-CRT): RT delivered by conforming Radiation dose around tumor. Spares some normal tissue
• Intensity Modulated Radiotherapy (IMRT): A Highly developed form of 3DCRT, in which the radiation dose is tightly conformed around tumor. Spares most normal tissue.
• Image Guided Radiotherapy (IGRT): IMRT delivered in conjunction with a daily CT scan of patient done by the treatment machine. Used to account for changes in size of tumor and accurately adjust for variations in normal tissues.
• Spatial Co-operation - 'The Steel Paradigm'
• Scenario where full strength CT & RT act independently, with Non-overlapping Toxicity Profiles
• Ideally, RT (Local Control) + CT (Systemic Control) = Improved outcomes
• Few CT agents meet this criteria due to - Limited Single agent activity + Toxicity driven dose reductions
• In Field Co-operation
• Scenario where CT & RT act together to increase Tumor cell kill.
• Full Dose RT (Local Control) + Reduced Dose CT (Enhances RT effect + Cytotoxic Effect) = Improved outcomes
• Strictly, Radiosensitizer - Enhances RT effect ONLY (e.g. Misonidazole)
• Low Dose CT - Radiosensitizer + Cytotoxic effect
• If Antagonistic action, then Radioprotective
• Brain Tumors - Maximal safe resection followed by Adjuvant RT
• Recommended for all WHO Grade II/III/IV tumors.
• Head & Neck - Organ Preservation Approach
• Nasal Cavity + ParaNasal Sinus: Adjuvant RT for close/positive margins, PeriNeural Invasion (PNS - Adenoid Cystic Histology). Adjuvant CCRT for Lymph Node +ve
• Oral Cavity Cancers - Adjuvant RT for Close Margins, Stage III/IV, Lymphovascular/ PeriNeural Invasion +ve, Oral Cavity Ca with Level IV/V Lymph Node +ve. Adjuvant CCRT for Margins +ve, Extracapsular spread +ve.
• Oropharynx, Larynx, Hypopharynx - Upfront surgery not preferred. If performed, Indications remain the same as for Oral Cavity Ca. Additional Indications for Adjuvant RT - pN2-N3, Cartilage Invasion (+ Greater than 1 cm subglottic invasion - Larynx only)
• Salivary Glands - Adjuvant RT for Close/ positive margins, Intermediate-High Grade, Adenoid Cystic Histology, LVI/ PNI, T3-T4, LN +ve
• Medullary Carcinoma Thyroid: Adjuvant RT for Positive margins, Extensive LN +ve, T4a.
• Lung Cancer - All patients should receive Adjuvant treatment
• NSCLC - Resectable stage I/II: Adjuvant RT for Close (<5 mm)/ Positive Margins.
• GI Cancers
1. Esophagus: Resectable Node -ve (Non-Cervical). Unfavorable T2N0, T3/T4, N+ve or Close/Positive margins - Adjuvant CCRT (RT + Cisplatin/5-FU)
2. Stomach: Resectable Node +/ -ve. Adjuvant CCRT (Mc Donald's - RT + Leucovorin/5-FU).
3. Pancreas: Resectable. Adjuvant treatment controversial. Adjuvant Chemo (Gemcitabine) followed by CCRT (RT + 5-FU) - suggested
4. GB: Resectable T1b or advanced. Adjuvant CCRT (RT + 5-FU)
5. Biliary Tract (Intra/ Extra - hepatic): Resectable with Residual disease. Adjuvant CCRT (RT + 5-FU - Stereotactic RT preferred)
6. Colo-Rectal: Resectable Stage I - Adjuvant CCRT for T2(RT + 5-FU). Stage II/III - Chemo(5-FU) followed by CCRT(RT + 5-FU) followed by Chemo(5-FU) vs NeoAdjuvant CCRT (RT + 5-FU) followed by surgery followed by Chemo (5-FU)
7. Anal: Resectable T1-T2, Node -, Close or positive margins. Adjuvant CCRT (RT + 5-FU/ Mitomycin)
• Breast - RT is an integral part of Breast Conserving Treatment (BCT). Even patients undergoing Mastectomy need Post Mastectomy RT (PMRT).
• In situ disease: BCT for DCIS
• Early Stage (I-IIB +/- T3N0): BCT vs Total Mastectomy + PMRT for T3/T4, positive margins, extracapsular spread and 4 or more Axillary nodes.
· For T1-T2, 1-3 Axillary nodes: Consider PMRT for 20% or more positive nodes, size, margins, LVI, Age, Grade
· For T1-T2, N0: Consider PMRT for Close/positive margin, Age, LVI, Grade
• Locally advanced: Chemo followed by Surgery. Mastectomy or BCT
• Bladder - Non Muscle Invasive: Adjuvant RT for Abnormal Cytology, Multifocal Disease, High Grade histology, Subtotal Resection
• Prostate - Adjuvant RT for Margins +, Residual disease on Imaging/Biopsy or pT3 disease
• Urethral - NeoAdjuvant RT for Distal Lesions or Lesions involving the entire urethra
• Testicular - Seminoma (Limited to Testis): Adjuvant RT
• Penis - Organ Preservation Approach - Increasingly favored based on Anal & Vulvar Ca results. Adjuvant RT for Node +
The indications for Definitive Radiotherapy/CCRT are numerous and continue to increase with ongoing Research.
Palliative Radiotherapy is an effective method of controlling some of the most distressing symptoms due to metastatic disease (irrespective of Primary).
Call us for More Details: