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BRACHYTHERAPY IN ORAL CAVITY

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the role of brachytherapy in oral cavity carcinoma.
physics of brachytherapy
radiobiology of brachytherapy
clinical application in tongue, buccal mucosa cancer

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BRACHYTHERAPY IN ORAL CAVITY

  1. 1. Brachytherapy In Oral Cavity Carcinomas Made by: Dr. Isha Jaiswal Moderator: Dr. Rahat Hadi Date: 25 Nov. 2014
  2. 2. Introduction  ‘Brachytherapy’ means short range therapy.  First form of conformal radiation therapy.  High dose intensification with rapid dose fall off.  Organ & function sparing.  Interstitial Brachytherapy – refers to implanting radioactive sources directly into the target tissues
  3. 3. History of Brachytherapy 1898: Marie & Pierre Curie isolated Radium 1938: Manchester System by Paterson-Parker 1964: Bernard Pierquin et al. used Ir192 after-loading interstitial implant 1978: Paris System – Pierquin and Dutreix 1980-90s: remote after-loading , computer planning & optimization New possibilities in Interstitial Brachytherapy with advantages of remote after-loading & computer optimization
  4. 4. CLINICAL ASPECTS OF INTERSTITIAL BRACHYTHERAPY
  5. 5. Intent of treatment 1. Radical : Brachytherapy alone as treatment 2. Boost: EBRT  Brachytherapy to boost dose to the primary 3. As salvage therapy in recurrent cases who have been irradiated before or who are unfit for surgery
  6. 6. Brachytherapy in oral cavity carcinoma  Indications:  For T1 N0 and T2 N0 , tumour less than 30 mm in size, brachytherapy can be given as the sole treatment for primary tumour.  For larger tumours or those with positive nodes, ideally combined surgery and post operative radiation is preferable, if this is not feasible patients should have external beam radiation to the primary and node with brachytherapy as a boost to the primary.  Contra-Indications:  Patient unfit for the procedure eg. comorbidities  Target volume not definable/ indistinct margins  T4 disease with bone involvement  Tumor access difficult
  7. 7. SELECTION CRITERIA  Easily accessible lesions  Early stage diseases (Ideal implant ≤ 5 cm)  Well localized tumor to organ of origin  No nodal or distant metastases  No local infections or inflammation  No comorbidities :DM / HTN  Proliferative/ ulcerative lesions preferred.  Favorable histology- mod. diff. i.e. SCC
  8. 8. General concepts based on ABS recommendation
  9. 9. The ABS recommends the use of brachytherapy as a component of the treatment of head-and-neck tumors. Much of the implant process of HDR is similar to LDR No definite evidence on use of concomitant chemotherapy; risk of increased mucosal toxicity compromising treatment – however, appears to be useful for the treatment of recurrences regarding the sequencing of EBRT and brachytherapy, it may be advantageous to obtain shrinkage with EBRT before applying brachytherapy in advanced tumors In case of brachytherapy boost, placement of radio-opaque markers before starting EBRT can help delineate the target volume, before any shrinkage occurs The dose prescription volume and dose points should be clearly specified
  10. 10. Dental Preparation  Teeth with caries should be restored. Teeth with deep caries or poor periodontal support must be removed and complete healing obtained before starting RT.  A prosthesis (made of acrylic resin) including lead shielding (2mm thick) should be made for brachytherapy of the lips, tongue, and floor of mouth, to reduce dose to the mandible and prevent osteoradionecrosis.  The shielding is worn by the patient during whole duration of irradiation, to protect teeth, gum, and mandible as it reduces the transmitted dose by about 50%
  11. 11. Important Facts to be Noted in H&N Brachytherapy CLINICAL: Based on ABS recommendations Accurate assessment of :tumor dimensions, neck node, lesion type via clinical examination & pre-treatment imaging: CT & MRI Feasibility for Brachytherapy: Mouth opening, dental status, proximity of bones to tumor requirement of dental shields/spacers Requirement of tracheostomy Fitness for anaesthesia
  12. 12. Important Facts to be Noted in H&N Brachytherapy PHYSICAL: Based on ABS recommendations Dose distribution even in a good implant is likely to be non-homogenous (due to complex geometry) Even minor displacement may produce significant hot/cold spots; increased morbidity/recurrence Peripheral fall off- may cause under-dosage of a site especially at borders Interstitial edema may produce alteration in dose distribution calculated to an extent of 10-15%.
  13. 13. PHYSICAL: The isodose distribution should be computer optimized, whenever possible, to conform to the CTV. The method of optimization should be noted.  The dwell times can be adjusted to minimize dose inhomogeneity. It must be stressed that whereas optimization can make the isodose distribution more homogenous, optimization vshould not be used as a substitute for good catheter placement
  14. 14. Important Facts to be Noted in H&N Brachytherapy BIOLOGICAL: – Total duration of EBRT + Brachytherapy should be kept as short as possible (<8 weeks) to minimize tumor cell repopulation – Interval between EBRT and Brachytherapy should be as short as possible (<1–2 weeks) depending on degree of recovery from mucositis – Interval between twice daily HDR fractions should be as long as possible (minimum of 6 hours) – Previous irradiation history for dose calculation
  15. 15. ABS Recommendations for recurrent head & neck cancer  Strongly emphasizes on using brachytherapy for recurrent tumors The extent of disease should be carefully studied with CT, MRI, or PET scan as necessary. Complication risks are increased in patients with previous surgery, skin or mucosal ulceration, deep soft tissue necrosis, bone exposure, or severe fibrosis. Meticulous implant technique and adequate doses are necessary. Generally larger margins are required for recurrent tumors, especially if additional EBRT is not applied. Because of the paucity of published data, the ABS cannot make specific recommendations for the indications for HDR brachytherapy in recurrent head and neck tumors. However, in view of the normal tissue tolerance, it is advisable to keep the dose per fraction relatively small.
  16. 16. N=220
  17. 17. Typical stages of a brachytherapy procedure. 2D PLANNING 3D PLANNING
  18. 18. Prerequisites for brachytherapy treatment Target Volume  The aim should be to treat the gross tumour volume which is usually palpable plus a margin of at least 1 cm all around it. Pre-planning:  measure the tumour carefully.  plan the exact number of radiation sources to be used with their length and separation.
  19. 19. Techniques Of Implantation  The two commonest techniques used for brachytherapy in the oral tongue are:  hypodermic needle technique  guide-gutter technique .  Plastic loop technique  Brachytherapy sources should always be implanted in an operating room equipped for anesthesia, with adequate lighting and suction facilities and the means to deal with extensive bleeding  The brachytherapy technique should be based on a classic system for interstitial brachytherapy (like those designed in Paris, Manchester etc)
  20. 20. Hypodermic Needles •Hollow, bevelled needles with outer diameter of 0.8mm and variable length (4 to 8 cm), open at both ends. • Cause little trauma - can be directly inserted in the tissues •The rigid steel and template system avoids displacement of the sources due to the elasticity of the soft tissues •Can be used in lip tumours of ≤3cm in largest diameter, not involving the lateral commissurae.
  21. 21. Guide-gutter technique: • Iridium hairpins with a fixed separation of 12 mm are used • This limits width of volume which can be treated to approximately 15 mm and the technique can therefore only be used for smaller tumours (≤30 mm in length). • The guide gutter is first inserted and when they are in position, the radioactive hairpins can be cut to the desired length • The pre-prepared suture is then tied over the bridge of the hairpin to secure it within the tongue
  22. 22. Plastic-Tube Loop Technique: Advantages: • This allows a wider separation between the sources - can be used to treat larger volumes. • Remote after-loading that reduces the risk of exposure • In case of local oedema inducing the risk of displacement of the plastic tubes, one can wait for an acceptable local status before loading the iridium wire. • Self retaining assembly, no suturing required
  23. 23. Prognostic factors for brachytherapy in oral cavity
  24. 24. A:tumour size is one of the most important prognostic factors. 1:The largest retrospective analysis was done by Pernot of 448 patients with tongue carcinoma and showed the critical role of tumour volume on local control as well as on loco regional control and survival rate. ( Pernot M, Malissard L, Hoffstetter S. The study of tumoral, radiobiological and general health factors that influence results and complications in a series of 448 oral tongue carcinomas treated exclusively by irradiation. Int J Radiat Oncol Biol Phys 1994; 29: 673-9.) 2:In the Gustave Roussy experience for patients treated by brachytherapy alone, tumour size also plays a role in local control: in 269 patients with mobile tongue carcinoma, the local control rate was 93%,86%, 69% for T1, T2, T3 lesions respectively. (Gerbaulet A, Haie-Meder C, Marsiglia H, et al. Role of brachytherapy in the treatment of Head &Neck cancer. Selectron Brachy J, 1992; 3: 15-20.) 3:Mazeron studying the influence of other tumour characteristics, showed (in a series of 166 patients with cancer of the mobile tongue treated by iridium implant alone that infiltrating tumours recurred in 22% of cases, whereas only 9% of superficial ones did. Mazeron JJ, Crook JM, Marinello G, et al. Prognostic factors of local outcome for T1, T2 carcinomas of oral tongue treated by iridium 192 implantation. Radiother Oncol 1990; 19: 281-5.
  25. 25. Prognostic Factors For Local Control & Complications In Interstitial Brachytherapy Head And Neck  Dose to mandible  Intersource spacing  Treatment volume  Safety margin  Dose rate, total dose, dose per fraction  Time delay
  26. 26. Factors Affecting Local Control: Indian data N=28 Factors influencing LC-  dose rate  source activity,  interplaner distance,  discontinuity in prescribed isodose
  27. 27. PHYSICAL ASPECTS OF INTERSTITIAL BRACHYTHERAPY
  28. 28. CHOICE OF RADIONUCLIDE  depends on several relevant Physical and Dosimetric characteristics  Ideal brachytherapy source must have following properties:  Pure γ emitter – less α/β emission Medium γ energy – high enough to target tumor with homogenous dose & low enough to avoid normal tissues & reduce shielding needs  High specific activity – small size & suitability for HDR  Stable ( not liquid/gaseous) daughter product  t ½ for permanent/temporary implant  Should be available in a form which does not powder or disperse if source is damaged or dispensed
  29. 29. Brachytherapy sources:  Brachytherapy can be accomplished with either :  rigid cesium-137 needles  iridium-192 (192Ir) sources afterloaded into angiocaths.  The most common technique is afterloading with 192Ir .  Guide needles can be inserted either free-hand or with the aid of a custom template to help maintain optimal source spacing
  30. 30. Dose, dose rates & fractionation: NCCN 2014 HIGH DOSE RATE a. Brachy Alone : 45 – 50 Gy @ 3-4Gy/# bid b. External + Brachytherapy Ext : 40-50 Gy in 4 1/2 - 5 1/2 wks. Brachy : 21 Gy @ 3 Gy/# LOW DOSE RATE(@0.4-0.5gy/hr) a. Brachy Alone 60 - 70 Gy in 6 to 7 days. b. External + Brachytherapy Ext : 40-50 Gy in 4 1/2 - 5 1/2 wks. Brachy : 20-35 Gy in 2-3 days
  31. 31. HDR Vs LDR :Indian evidence N=84
  32. 32. LDR  Superior radiobiological role.  Minimum intersession variability in dose distribution HDR  SHORT T/T TIME  Geometry well maintained  Better patient compliance / comfort  Day care procedure  OPTIMIZATION  NO RADIATION HAZARDS  SMALL APPLICATOR  Less tissue trauma ADVANTAGES
  33. 33. RULES OF IMPLANTATION  Depending on the size of the lesion a single plane, double plane, or volume implant can be used to cover the tumor with a 1-cm margin.  For tumors <1 cm in thickness, single plane implants are adequate.  1-2.5 cm thickness double plane implant  > 2.5 cm thickness volume implant  Surface mold radiation can also be considered for small tumors <1 cm depth or superficial lesions of the lip, hard palate, lower gingiva, and floor of the mouth.  For lesions exceeding 2.5 cm, it is difficult to avoid significant cold spots in the implant volume.  It must be borne in mind is that as tumors get too close to the mandible or are large in volume, the risk of osteoradionecrosis increases
  34. 34. DOSIMETRY IN INTERSTITIAL IMPLANT:  Paterson-parker system  Quimby system  Paris system  Computer system
  35. 35. TYPESOF IMPLANTS
  36. 36. For volume implants, AL should be at least 7.5% longer than TL for each uncrossed end.
  37. 37. P-P Tables The P-P tables are designed to give milligram hours / 1000 roentgens for various implant sizes both for planar and volume implants depending on the surface area of implant. To convert the P-P tables from roentgens into rad in tissue one needs to account the following corrections.
  38. 38. ICRU-58
  39. 39. Volumes:definitions Gross Tumor Volume (GTV) The palpable or visible/demonstrable extent and location of the malignant growth. Clinical Volume (CTV) The volume of the tissue that contains a gross tumor volume and/or sub clinical microscopic malignant disease which has to be eliminated. Planning Target Volume (PTV) The volume of tissue receiving the prescribed irradiation. For an interstitial brachytherapy, the PTV is, in general, identical to the CTV. Treatment Volume (TV) The volume of tissue, which is encompassed by an isodose surface that has been specified by the radiation oncologist. The dose value at this isodose surface is the minimum target dose
  40. 40. Central Plane The plane that is perpendicular to the main direction of the linear sources and passing through the estimated center of the implant.
  41. 41. Prescription Dose  The prescribed dose is defined as the dose, which the physician intends to give, and enters in the patient’s treatment chart.  Mean Central Dose Calculated as average of doses to mean central dose points  Minimum Target Dose (MTD): The minimum dose at the periphery of the CTV = Minimum dose decided upon by the clinician as adequate to treat the CTV (minimum peripheral dose).  MTD ≅ 90% of the prescribed dose for interstitial therapy
  42. 42. Prescription Dose Low Dose Volume  A low dose volume should be defined as a volume within the clinical target volume, encompassed by an isodose corresponding to 90% of the prescribed dose. High Dose Volume  The volume of tissue that is encompassed that will receive more than 150% of the mean central dose be reported.
  43. 43. ICRU (58) recommendation for reporting interstitial brachytherapy Description of the clinical, including GTV, CTV Description of the techniques Source specification Treatment prescription Mean Central Dose (MCD), Minimum Target Dose, Homogeneity Index Volumes and their dimensions, including PTV, Treatment Volume,  High-dose regions, low-dose regions, reference volume, irradiated volume
  44. 44. CLINICAL APPLICATION OF INTERSTITIAL BRACHYTHERAPY
  45. 45. CLINICAL APPLICATIONS Oral Cavity:  LIP:  Indications: T1-2N0 Lesions  T.V.: All visible & palpable tumour with 5-10 mm margin  Dose: 50-70Gy in 5-7 days LDR  Technique:  Rigid afterloading needles maintained in place by Template  Classical plastic tubes  Spacers to decrease dose to gingiva, teeth & other lip
  46. 46.  1a&b: T1 squamous carcinoma, manifesting an ulcerous tumour affecting an external third of the inferior lip.  1c: Brach- therapy using rigid needles technique for LDR 192Ir sources  1d: tumour 2 months after brachytherapy with excellent cosmetic and functional results
  47. 47. CLINICAL APPLICATIONS… Oral Tongue:  Indications: T1 N0, T2 N0 < 3cm lesion  T.V.: GTV + 5 mm margin  Dose: Alone:60-65 Gy LDR  Boost 20-25 Gy after EBRT dose of 45-50 Gy  Techniques: Guide-gutter technique  Floor of Mouth:  Indications: T1-2N0 lesions, ≥ 5 mm away from mandible  Dose: Techniques same as for Tongue implants  Complication: Osteoradionecrosis:5-15% AP X-ray
  48. 48. Advantage of Brachytherapy  Delivers localized dose to the tumor  Rapid dose fall off outside the target volume allows excellent normal tissue sparing  Less intergal dose as compared to 3DCRT & IMRT  High biological efficacy  Decreased risk of tumor population  Elimination of set up errors as the source maintains a fixed relationship to target volume  High tolerance: Tolerable acute intense reaction  High control rate  Better cosmesis: May avoid disfigurement and mutilating surgery  Minimal radiation morbidity  Day care procedure  Organ preservation  Reirradiation for localized recurrence
  49. 49. Limitation of brachytherapy  Difficult for inaccessible regions  Limited for small tumors (T1-T2)  Nodal disease cannot be covered simultaneously  Invasive procedures, require GA  Greater conformation –small errors in placement of sources lead to extreme changes from the intended dose distribution  Quality of implant is operator dependent  Radioactive hazards (not now)
  50. 50. Decline in use of brachytherapy  Over the past decade or more improvements in reconstructive surgery techniques have diminished the practice frequency of brachytherapy in the treatment of oral cavity carcinoma.  In addition, a diminishing percentage of radiation oncologists remain highly skilled and experienced with the requisite implant techniques.  Finally, the steady advancement of highly conformal external beam techniques (IMRT, tomotherapy) has contributed to less frequent practice of brachytherapy in head and neck cancer overall.
  51. 51. Intraoral Cone  enable boosting of radiation dose to sites within the oral cavity while avoiding direct dose to the mandible  best suited for anterior oral cavity lesions in edentulous patients.  Treatment with intraoral cone involves either 100 to 250 kilovolt (peak) (kvp) x-rays or electron beams in the 6 to 12 MeV range  Lesions up to 3 cm are amenable to treatment with intraoral cone  requires careful daily positioning and verification by the physician. For this purpose the device is equipped with a periscope to visualize the lesion.  The cone abuts the mucosa and is centered directly over the lesion.  Intraoral cone treatment should take place prior to external beam radiation so that the lesion can be adequately visualized.

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