Brachytherapy.pptx

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1. Radioisotopes and Dose Rates in Brachytherapy

2. RA D IOISO T OPES An unstable form of element that emit radiation to transform into stable form These are mostly artificially produced in research reactor or accelerators by exposing the target material to particles such as neutron or protons.eg. Co59 + neutron = Co60

3. Brachyt h erapy Definition: It is a method of treatment in which sealed radioactive source are used to deliver radiation at a short distance by various methods. Brachytherapy developed largely through the use of sealed radium and radon sources. In the 1950s, alternative artificially produced nuclides became available. Gradually radium and radon were replaced with 137Cs, 192Ir, 60Co, 198Au, and 125I sources

4. Properties of brachytherapy sources and radionucleides Clinical utility of any radionuclide depends on Half life Radiation output per unit activity Specific activity (Ci/gm) Photon energy Whereas Methods of producing radionuclide, its physical and chemical properties determine its cost effectiveness and toxicity

5. Some Terms which will be used frequently : Radioisotopes Brachytherapy Activity Half life Specific activity Air Kerma Reference air Kerma rate Exposure rate Exposure rate constant

6. IMPORTANT DEFINITIONS Radioactivity: No. of disintegrations per unit time (sec ,min,hrs.) expressed in curies 1 curie (ci)=3.7x10 10 disintegration /sec 1 Bequerel (Bq) =1 disintegration / sec. (S.I.unit) Half life(T1/2): “The time required for a radioactive isotope to lose half of its original activity .” Half Value layer (HVL): The thickness of the specified substance that when introduced into the path of radiation coming from source, reduces the exposure rate

7. Kerma (dEtr/dm) Where dEtr is the sum of initial kinetic energy of all the charged ionizing particles released by uncharged particles in a material of mass dm. Unit : J/Kg Air Kerma Strength Air kerma strength is defined the product of air kerma rate in free space and the square of distance of the calibration point for the source center along the perpendicular bisector. Unit : J m 2 /kg-hr

8. REFERENCE AIR KERMA RATE (RAKR) “the kerma rate to air, in air, at a reference distance of 1 m,corrected for air attenuation and scattering”. µGy/ h at 1 m µGy /s at 1 m and mGy /h at 1 m LDR HDR

9. TOTAL REFERENCE AIR KERMA There are steep dose gradients in the region of the sources, so that specifying a treatment in terms of the dose at a point is not recommended. TRAK IS THE SUM OF THE PRODUCTS OF RAKR AND THE DURATION OF THE APPLICATION FOR EACH SOURCE independent of the source geometry and proportional to the integral dose to the patient. compare treatments within one centre or between different centres and to explain possible differences in the delivered dose or in the treatment volume dimensions. useful index for radiation protection of personnel

10. Types of Brachytherapy B r a c h y ther a py Types of implant Interstitial Intracavitary Intraluminal Intravascular Surface Mould Dose rate of irradiation LOW DOSE RATE (LDR): 0.4-2 Gy/hr MEDIUM DOSE RATE (MDR): 2-12 Gy/hr HIGH DOSE RATE (HDR): > 12 Gy/hr Treatment Duration TEMPORARY PERMANENT Source Loading Preloading A fterl o a d i n g

11. Radioisotopes in Brachytherapy Radium Discovered by Madam Curie in 1898 Naturally occuring radionucleide Complex decay scheme 1 st used in 1906 in clinics, led to Radiation Necrosis due to intense beta ray dose from the Radium 1920 : successful filtration of the beta rays was achieved

12. Ra d ium Cascade of transformation of one daughter product to another ending with stable isotope of Lead 206

13. RADIUM-226 88 Ra 226 → 86 Rn 222 + 4 He 2 H 1. Gamma E n ergy .184 - 2 . 5 4 MeV (av g . e n ergy - . 83 MeV) Beta Energy Half life Specific activity 5. HVL Exposure Rate Const. Spectrum Encapsulation Physical form . 7 - 3 . 2 5 MeV 1600 years 0.97 Ci /gm 12mm of Pb. 8.25 Rcm 2 /mg-hr wide range of 49 gamma rays 0.5 mm Platinum. Tubes, Needles

14. Radium sources are specified by (a) active length, the distance between the ends of the radioactive material; (b) physical length, the distance between the actual ends of the source; (c)activity or strength of source, milligrams of radium content; (d) filtration, transverse thickness of the capsule wall, usually expressed in terms of millimeters of platinum.

15. WHY RADIUM IS NOT USED NOW A DAYS Daughter products, RADON is an alpha emitter. It is a Gas which is soluble in tissue. Not easily detected by a visual check can escape through hairline crack in the radium capsule Radium and its daughter products may become deposited more or less permanently in the bone if ruptured within patients body Radiation protection for these sources requires large thicknesses of lead, which can cause problems when it comes to: Transporting sources in heavy containers. Using very heavy protective screens around the patient. The need for a heavy rectal shield in applicators used for gynecological treatment. Sources of higher activity are bulky and not suitable for

16. Properties of the Ideal Brachytherapy Source. Ideal radionuclide should produce a single gamma ray spectrum with energy of around 0.5 MeV. acceptable half life Cheap and easily produced Preferably solid Stable solid decay products High specific activity Closest to the ideal radionuclide for LDR at present time is Cesium 137

17. Radium Substitutes The first sources to be used as alternatives to radium were Cobalt-60, Gold-198, Cesium-137 and Iridium-192.

18. Cesium discovered in the late 1930s by Glenn Seaborg and Margaret Melhase Product of nuclear fission with beta rays 0.662 MeV. 0.5-1.17 MeV 30 yrs 10 Ci/gm. 5.5 mm of Pb 3.26 R cm 2 /mCi-hr. Single Gamma ray 0.5 mm of Pt. Needles, microspheres, powder Gamma Energy - Beta Energy - Half life - Specific activity - HVL - Exposure Rate Const - Spectrum- Encapsulation - Physical form- 2% annual reduction in source activity occurs

19. Source specification insoluble powders or ceramic microspheres, labeled with 137 Cs, and doubly encapsulated in stainless steel needles and tubes.

20. Cobalt 60 Properties of Cobalt 60 Production : by neutron activation of the stable isotope cobalt-59 Half Life : 5.27 years Decay Scheme : 27 Co 60 28 Ni 60 + -1 β + γ Beta energies : 0.318 MeV Photon energies : 1.17 MeV and 1.33 MeV Beta filtration : typical source wall thickness Half value layer in lead : 10 mm

21. Form of source Co 60 Cobalt brachytherapy sources are usually fabricated in the form of needle An alloy wire composed of 45% cobalt & 55% nickel, so called cobanic Encapsulated in a sheath of platinum of stainless steel Because cobalt tends to be corrosive, it is usually nickel plated; encapsulation with 0.1 mm to 0.2 mm platinum- equivalent is necessary to filter the b-particles.

22. Iridium 192 Used for HDR brachytherapy Properties of Iridium 192 Production : by neutron activation of the stable isotope Iridium 191 Half Life : 73.83 days Decay Scheme : 77 Ir 192 78 Pt 192 + -1 e + γ Beta energies : 0.079-0.672 MeV Photon energies : 0.2 – 1.06 MeV Beta filtration : 0.1 Platinum Half value layer in lead : 4.5 mm

23. Most common form of source : wire in 1 m length coils, wire consists of an active iridio platinum core, 0.1 mm thick, encased in a sheath of platinum, 0.1 mm thick

24. iridium seeds seeds are 3 mm long and 0.5 mm in diameter Made up of 30% Ir + 70% Pt surrounded by 0.2 mm thick stainless wall pure iridium is very hard and brittle, and is difficult to fabricate.

25. GOLD 198 Au 19 7 + 1 n → A u 19 8 + Υ 0.412 MeV 0.69 MeV. 2.7 days 2.5 mm Pb 2.38 Rcm 2 /mCi– seed Gamma Energy: Beta Energy Half Life HVL : Exposure rate const. : hr Physical form: Used for permanent implant Gold seeds of size 2.5 mm long & 0.8 mm diameter

26. Advantages of Gold over others The average photon energy of gold is 0.406 Mev , making the radiation protection requirements much easier and cheaper to implant than those of Ra 226 , Rn, Co or Cs Very short half life so useful for permanent implants

27. IODINE 125 • Xe 124 n Xe I + 1 → 125 → 125 0.028 MeV (avg). None 59.4days 1739 Ci/gm 0.025 mm OF Pb Three gamma rays 1.46 Rcm 2 /mCi–hr 0.5 mm titanium seed Allen Reid and Albert keston discovered I 125 in 1946 Gamma Energy - Beta Energy- Half life - Specific activity - HVL - Spectrum - Exposure rate const. - Encapsulation - Physical form- Used for permanent interstitial implants.

28. 125 I decays by electron capture to an excited state of 125 Te which decays to ground state releasing 35.5keV . IODINE FROM FM KHAN

29. The high specific activity of I 125 enables the production of miniature sources sufficient activity for use in both permanent and temporary implants The main current application field of I 125 is permanent interstitial implant for prostate cancer

30. Palladium 103 46 Pd 102 + n 1 → P d 103 46 Gamma Energy : Beta Energy: Half life : Specific activity HVL : Encapsulation : Exposure rate constant: 0.021 MeV (avg) None 17days 7448 Ci/gm 0.008 mm of Pb Titanium 1.48 Rcm 2 /mCi–hr. 103 Pd decays by electron capture (20-23 keV x rays)

31. Pd 103 has been introduced as replacement for I 125 sources for permanent implant Its short half life of 17 days makes Pd 103 only appropriate for permanent implants Its short half life and high specific activity enables dose delivery at initial dose rate higher than that of I 125 This feature is beneficial when used for rapidly proliferating tumors

32. Advantages of one over another Cs over Radium Reduced amout of shielding is required and absence of gaseous daughter product Cs over Cobalt Longer half life of 30.07 years compared with 5.27 years of Co, which enables the clinical use of Cs source over a long period of time Low production cost Smaller amount of shielding required Disadvantages of Cs Lowest specific activity, doesnot allow the production of miniature sources of very high activity for HDR remote controlled loading BT Thus appropriate only for LDR

33. Cobalt over Cs Due to high specific activity, Co is appropriate for fabrication of small high activity source Cobalt over Radium Cobalt wires can be bent to conform to the shape of tumor No danger of leakages or breakages cobalt over iridium Half life of cobalt is much more than of iridium, hence it need not to be replaced as frequently as iridium 25 source exchanges are required for 192 Ir for one exchange of a 60 Co source THOUGH INTEGRAL DOSE IS HIGHER IN CO 60

34. Types of Brachytherapy…… Depending on source loading pattern: Preloaded: inserting needles/tubes containing radioactive material directly into the tumor After loaded: first, the non-radioactive tubes inserted into tumor Manual: Ir 192 wires, sources manipulated into applicator by means of forceps & hand-held tools Computerized remote controlled after loaded: consists of pneumatically or motor-driven source transport system

35. Preloading pattern Advantage: Loose & flexible system(can be inserted even in distorted cervix) Excellent clinical result Cheap Long term results with least morbidity (due to LDR) Disadvantages: Hasty application -Improper geometry in dose distribution Loose system – high chance of slipping of applicators – improper geometry Application needed special instruments to maintain distance. Radiation hazard

36. After loading pattern MANUAL AF T ERLO A D ING Advantages Circumvents radiation protection problems of preloading Allows better applicator placement and verification prior to source placement. Radiation hazard can be minimized in the OT / bystanders as patient loaded in ward. Advantages of preloading remain. Disadvantages: specialized applicators are required.

37. REMOTE AFTERLOADING Advantages : No radiation hazard Accurate applicator placement -ideal geometry maintained -dose homogeneity achieved -better dose distribution Information on source positions available Individualization & optimization of treatment possible Higher precision , better control Decreased treatment time- opd treatment possible Chances of source loss nil . Disadvantages : 1. costly

38. Different dose rates used for brachytherapy treatment dose rates fall into these categories: Ultra LDR : 001 to 0.3 Gy/hr : dose rate used in permanent implants with I 125 and Pd 103 LDR : 0.4 to 2 Gy/hr, compatible with conventional manual or automatic after loading technique MDR : 2 – 12 Gy/hr, can also be delivered by manual or automatic afterloading, although the latter is far more frequent HDR : >12 Gy/hr and only automatic afterloading can be used because of the high source activity PDR : pulses of 1 to 3 Gy/hr, delivers the dose in a large number of small fractions with short intervals Permanent Implants : deliver a high total dose (eg.

39. Sources for LDR intracavitary brachytherapy Active length should be 1.3 to 1.5 cm Half Life should be 5 to 10 years working life without variation in prescription dose rates Average photon energy : 60 to 100 keV Sources : Radium 226 and Cesium 137

40. Sources for permanent Interstitial Brachytherapy 2 Basic approach Classical LDR permanent brachytherapy Radon 222 Au 198 seeds HALF LIFE : FEW DAYS High energy photons Patient must be confined to the hospital until the source strength decays to safe level (10 days)

41. 2. ULDR brachytherapy Larger lives but low energy emitters – Pd 103 and I 125 Patients tissue or thin lead foils are sufficient to limit exposure to negligible levels No need to hospitalize patients solely for radiation protection During the implant procedure, decreased radiation exposure to O.T. persons

42. Sources for HDR brachytherapy Uses high intensity source to deliver discrete fractions ranging from 3 to 10 Gy A remote after loading device must be used Radio-nuclide with high specific activity (Ci/gm) is needed so that treatment dose rates of at least 12 Gy/hr can be achieved. A miniature source no longer than 1 mm diameter and 4 mm length with an exposure rate of 1 R/sec at 1cm is required.

43. The radiobiology of brachytherapy Brachy : not only short treatment distance but also short treatment time Short overall treatment time, compared to EBRT minimizes tumor repopulation in rapidly growing tumors Short overall treatment time in brachytherapy are likely to contribute significantly to clinical efficacy for tumor sites like cervix, head and neck and lung where long overall treatment time is associated with reduced local control.

44. Radiobiology of the brachytherapy and Dose Rate Effect The biological effects of radiotherapy depends on Dose distribution Treated volume Dose rate Fractionation and Treatment duration However these are of different importance in determining the outcome of EBRT and of brachytherapy

45. Radiobiological difference between EBRT and brachytherapy Factors EBRT Brachytherapy Volume treated Large Very small Dose homogenity -5 to +7% acceptable Very inhomogenous Volume effect relationship >tolerance dose, not well toleraable Very high doses tolerated well Time dose factors Small daily fractions of few seconds/minutes Continuous deliver and short treatment

46. Radiobiological Mechanisms The bilogical damage inflicted by irradiation of human cells can be divided into three consecutive steps : Physical phase : short initial phase, excitation of electrons and ionisation, energy deposition phase Chemical Phase : ionized and excited atoms interact directly or indirectly through the formation of free radicals to the breakage of chemical bonds. Biological Phase : Longer phase, seconds to years, cells reaction to inflicted chemical damage, specific repair enzymes successfully repair the majority of DNA lesions, however few may not repair and lead to cell death. Early reactions Late reactions

47. Radiobiology – LDR Vs HDR In terms of 4Rs Repair : LDR : allows time for sublethal damage repair in normal tisues HDR : short treatment time prohibits this repair Reassortment : LDR : theoretic advantage of an improved result HDR : --- Only shown in vitro, but in vivo the effect of reassortment has not been shown to give a true advantage, possibly due to disruption of the mechanism of cell cycle in cancer cells

48. Repopulation LDR & PDR : probably prevents repopulation during treatment HDR : short treatment time, so no issue of repopulation Reoxygenation : 2 types of hypoxia : chromic and transient LDR : transient hypoxia may correct during treatment time HDR : not possible If brachytherapy is fractionated, tumor shrinkage and re-oxygenation of areas of chroni hypoxia may occur between insertions

49. Biophysical Modeling of Brachytherapy In 1970s, before the diffrential response of early and late responding tissues was understood, the most widespread approach for designing alternative fractionation schedule was Nominal Standard dose equation (NSD) This equation was based on data from early responding tissues and it didn’t account for diffrential response to fraction size/dose rate of early Vs Late effects

50. Linear Quadratic Model Distinguishes between early and late response Based on mechanistic notion and how cells are killed by radiation After several decades of investigation and use, LQ model have been well supported by clinical experience and outcome date

51. Mechanistic basis of LQ model In this approach radiotherapeutic response is primarily related to cell survival Cell killing is the dominant determinant of radiotherapeutic response both for early and late responding end points S(D)=e - αD-βD2

52. The Linear Quadratic Model T y p e A d a mages: Two Critical Target within a cell are simultaneously damaged (hit) in a single radiation interaction event leading to cell death Type B damages: Two critical Target are damaged in separate events, after which the damaged sites interacts to produce cell death Sub Lethal damages: The damages which are not so effective for lethality of cell

53. Linear component related to single track events, Quadratic component related to interaction of multi-track events low dose radiation single track events predominate and are far apart in time to produce any significant double track events. The high dose radiation Multiple track events predominate. Survival curve bends and becomes curved. dose E f curve is straight with no shoulder . f e c t e - e - e - Linear E α D Quadratic E α D 2 Basis of LQ model

54. The Linear Quadratic Model S parsely ionizing particles Densely ionizing pa rt icles β D 2 α D α / β 4 8 12 The expression for cell survival curve by this model P (survival) or SF = exp (-αd -βd2) 2 components of cell killing: T ype A damages – Cell Killing proportional to dose D i.e E, effect proportional to D Type B damages – Cell Killing proportional to the square of the dose D 2 . i.e E, effect proportional to D 2 Fowler (1989)

55. Low Dose Rate continuous Brachytherapy BED = D [1+g. R /(α/β)] Where Total dose = D = Dose Rate x Time = R.T g = incomplete repair factor g = (2/µT).[1-(1/µT).{1-exp(-µT)}] and µ = 0.693/t 1/2

56. Use of LQ model in Brachytherapy quantifing the rationale for LDR Lowering the dose rate generally reduces radiobilogical damage. For high dose rates, the dose reduction needed to match the late effects is larger than the dose reduction needed to match tumor control For any selected dose, increasing the dose rate will increase late effects much more than it will increase tumor control Conversly Decreasing dose rate will decrease late effects much more than it will decrease tumor control Thus the therapeutic ratio increases as the dose rate decreases

57. Use of LQ model in Brachytherapy quantifing the rationale for LDR

58. High Dose Rate Brachytherapy BED = D [1+d/(α/β)] Where D = n.d n = no. of fractions d = dose per fraction DNA Repairs doesn’t occurred in a short period of time of 10 min. DNA repairs occurs between two successive fractions only Bur for well spaced fraction >>12 hrs, Correction for incomplete Repairs is not required

59. Radiobiological principles involved in moving from LDR to HDR This is the case for cervical br a ch y th e ra py because bladder and rectum are generally some significant distance from implant

60. Brachytherapy for prostate cancer Optimized dose protraction for prostate cancer Brachytherapy Prostate tumors contain unusually small fractions of cycling cells Low α/β ratio So they behave like late responding normal tissues

61. Ca prostate : Brachytherapy Radiobiological Basis α/β value for prostate cancer is similar to that for surrounding late responding normal tissue, HDR could be employed to match conventional fractionated regimen with respect to tumor control and late sequalae while reducing early urinary sequalae The α/β value for grade 2 or higher late rectal toxicity is 4.8 and this value is larger than of the prostate tumor α/β ratio This suggests that HDR prostate Brachytherapy might actually improve the therapeutic outcomes of prostate cancr Brachytheapy

62. Advantages of HDR Over LDR Radiation Protection After loading No source preparation and transportation Only one source, there is no risk of losing a radioactive source Short treatment times Less discomfort to patient Low risk of applicator movement during therapy Treat large no of patients Smaller diameter Reduced dilation of cetvix After loading Treatement dose optimization Possible

63. Disadvantages of HDR over LDR Radiobilogic Short treatment times : no sublethal damage repair, no reassortment , redistribution and reoxygenation Limited experience The economic disadvantages Costly remote after loaders Required shielded room and more labor intensive Greater potential Risk High specific activity source used, if machine malfunctions or there is calculation error, there is very short time to detect and correct errors

64. Difference between LDR & HDR brachytherapy treatment Planning HDR BT differs from LDR BT in 3 Ways :- 1 st difference : time Course The patient waits in the treatment position during the treatment plan generation in HDR while Treatment plan generation performed with the patient elsewhere in LDR 2 nd difference : quantities involved with dose calculation HDR : one source strength and many different dwell times LDR : input – source strength input by user, many sources In both case, dose calculation algorithm uses the product of source strength and time at a given location 3 rd difference : role of quantities as input or output LDR : input : source strength and treatment duration HDR : reverse process start with dose pattern disingned and working backward to the dwell time distributing necessary to achieve that dose

65. Conversion from Low to High Dose rate Brachytherapy Biggest questions : How many fractions to use ??? What dose/fraction ???? Increasing the number of fractions increases therapeutic ratio but each additional fraction brings Costs for departmental resources and Inconvenience to patient So Most regimens use 5 or 6 #s if applicator insertions involved and 8 -12 #s if applicators can be left in place

66. Dose/# ???? BED HDR = BED LDR calculate dose/# α/β : comes into play again If normal tissue toxicity is kept constant, α/β = 3 If tumor cure is kept constant then α/β = 10 (or value of particular type of tumor) If late complications are to be kept constant then α/β=2 For intracavitary applications, normal tissue can be kept away from the applicator, which allow us to calculate dose based on equivalent tumor control

67. Experimental Results In vitro studies in sixties have shown that there is an effect of dose rate on cell survival This effect differs with cell type The dose needed for 1% survival is roughly 1.5-3 times higher at 1 Gy/hr than it is at 1 Gy/min

68. Pulse Dose Rate (PDR) Combined physical advantage of HDR BT and radiobiological advantage of LDR BT PDR BT was proposed and introduced as a method to replace continuous LDR advantages of PDR brachytherapy compared with LDR full radiation protection for caregivers no source preparation necessary no extensive source inventory, that is, only one iridium-192 source per afterloader to be replaced every 2 or 3 months

69. Compared with HDR brachytherapy, PDR offers similar quality of dose distribution, and similar treatment procedure and technical verification, both being stepping source technologies Clinical results : Ca Cervix source

70. Most Studies Local control : 80-90% Overall survival : 4 yrs for 55% Patients Low incidence of gr II GI and GU late toxicity Disadvantage of PDR PDR delivered by stepping source might behave more like HDR than LDR, Especially for tissues with a substantial component of repair of very short T1/2

71. 1990-1992, 180 patients, St IIB-III All patients received EBRT@ 45 Gy/25#/4.5 weeks Divided into two arms Dose reduction arm (30%) – 2450 cGy to Pt A Dose reduction arm (12.5%) – 3060 cGy to Pt A Vs Previously treated IIB and III patients with LDR (55-65 cGy/hr)

72. MDR – 30 : results were comparable to LDR group, so this group was retained MDR – 12.5 : discontinued due to increased morbidity So, decided to evaluate dose reduction between LDR and MDR 30 20% dose reduction was decided upon 2 nd 1 st : MDR –30 : MDR – 20

73. Summary No statistical difference in local control between LDR, MDR – 30, MDR -20 and MDR – 12.5 However significant increase in late complications with MDR -12.5 and higher trend seen with MDR - 20 So its important to know the absolute dose received by critical organs _ rectum and bladder

74. Clinical Results : LDR, MDR and HDR brachytherapy Many clinical data have been accumulated over the years in brachytherapy, but very few randomized trials. These retrospective studies help to better understand the biological background of brachytherapy and devise the rules that can be followed in clinical practise.

75. Results of HDR Vs LDR Cervical Cancer LDR brachytherapy : experience > 100 years It is very important to critically analyze how the results obtained with HDR Brachytherapy which has a much shorter history to be compared with LDR Meta Analysis By Orton et al, 56 institutes HDR : 17068 patients LDR : 5666 patients 5 year survival date was available for 6639 HDR S p t a a t g i e e nts and 3 3 H 6 D 5 R L D R pati e n t L s DR I 82.7% 82.4% II 66.6% 66.8% III 47.2% 42.6%

76. 1999, Pertreit and Peracy, Literature review 5619 patients with HDR treatment 5 year pelvic control rates were 91% for stage I, 82% for stage II and 71% for Stage III Patients 5 years OS was similar to previous metaanalysis 4 Randomised Studies by Shigematu et al Hareyama et al Patel et al and recently Teshima et al (2004) from thailand Which all of them have showed no difference in OS, RFS or Pelvic Control and No statistical difference in complication rates for rectum, bladder or small Bowel

77. Total no of patients = 423, EBRT @ 45 Gy/20# f/b Two groups LDR group : 220 pts, dose rate @ 55cGy/hr to 90 cGy/hr, dose 35 Gy in single inserrtion with Cs 137 HDR group : 203 patients, radionucleide Co 60 , dose 8.5 to 9.5 Gy to point A, 2 sessions

78. Results Patients with complete response after completion of treatment : 90 % LDR Vs 89 % HDR Recurrence cervical : 9 % LDR Vs 10 % HDR Parametrial : 12% LDR Vs 11% HDR, at last f/u, end of 5 yrs Overall control of disease : 72% with LDR and 72% with HDR

79. Ca Prostate Permanent implantation of I 125 or Pd 103 is the most common type of prostate Brachytherapy However several centers have used HDR Brachytherapy as a boost to EBRT with encouraging results Potential advantage of HDR Brachytherapy in prostate cancer is the theoretical consideration that prostate cancer cells behave more like late reacting tissues with low α/β , they should therefore respond more favourably to HDR fractions rather than LDR Brachytherapy

80. Galalae et al, 611 patients treated at 3 institutes with EBRT followed by Brachytherapy for localized prostate cancer Five year biochemical control : Low risk 96% Intermediate risk 88% High Risk 69%

81. Prostate cont..

82. Carcinoma Breast EBRT is standard radiation modality after Lumpectomy Over the past decade, increasing use of Brachytherapy as the sole modality of treatment to decrease the treatment time from 6 weeks to about 5 days ABS recommends : 34 Gy/10# to CTV when HDR Brachytherapy is used as the sole modality Data on use of HDR as boost is very limited

83. Polgar et al, 207 patients with stage I and stage II patients All patients underwent BCS f/b WBRT Two arms : No further treatment Radiation boost by either 16 Gy of electrons or HDR BT12 to 14 Gy 52 patients with HDR Boost 5 year local tumor control was 91.4% And excellent to good cosmesis : 88.5% Same results were obtained with electron irradiation

84. Esophageal Carcinoma Brachytherapy is relatively simple to perform because a single catheter is used for treatment Largest diameter applicator should be used to minimize the mucosal dose relative to dose at depth ABS recommends : HDR dose of 10 Gy in 2 #, prescribed at 1cm from source to boost 50Gy of EBRT

85. Sur et al, 1992, 50 patients with squamous cell carcinoma One arm : EBRT alone EBRT + HDBT 4 4 % Vs Another arm : (12Gy/2#) 12 month survival 78% Relief of dysphagia at 6 months 53.5% Vs 90.5%

86. For medically inoperable patients with submucosal esophageal cancer, EBRT with ILBT is an attractive approach Ishikawa et al, 5 year cause specific survival to be 86% with EBRT and ILBT and 62% with EBRT alone In pallilative setting to relieve dysphagia HDBT is more defined Sur et al, 50 Patients, EBRT @ 35 Gy/15#, 1 st arm : kept on f/u 2 nd arm : 12 Gy/2# HDR 6 month relief of dysphagia : 84% Vs 13% 1 year survival : 69% Vs 16%

87. Head and Neck Cancers Head and Neck area doesnot tolerate high dose per fraction Nasopharynx : Easily accessed by intracavitary HDR applicator Lovenderg et al, have shown patients most suitable for HDR BT boost are tghose with T1 and T2 lesion following 60 to 70 Gy of EBRT HDR of 18 Gy/6 # are delivered by special nasopharynx applicator T3, T4 : better suited to be boosted by IMRT

88. HDR Brachytherapy as salvage in H&N Cancer Loco-regional recurrence is the primary pattern of failure in H&N caners despite of advancement in surgery, concurrent CCT and EBRT Surgical Treatment is the preferred treatment, however it is not possible in all cases EBRT is as effective as salvage treatment but with high toxicity HDR BT has been used in previously irradiated patients, initial results appear to be comparable to other modalities

89. Conc l usion Beginning of brachytherapy started with the discovery of Radium. With the improvement in specific activity of sources the era of HDR came along with the decreased radiation exposure to the persons involved . Though theoritically , LDR is radio biologically better than HDR , clinical trials have shown the result of HDR as good as LDR .

90. ` Thank You