Ca cervix brachytherapy

1. BRACHYTHERAPY
IN CERVIX
Dr. S. Sachin,
Junior Resident,
Dept. of Radiotherapy and Radiation Medicine,
SSH, IMS, BHU

2. BRACHYTHERAPY
• Brachy (Greek) for short distance
• placing sealed radioactive sources
• very close to (or) in contact with (or) within
the target tissue
• in a geometric fashion.

7. BRACHYTHERAPY - ADVANTAGES
• The absorbed dose falls off rapidly with increasing
distance from the sources
• Inverse square law
• High doses may be delivered safely (sparing normal
tissue) to a localized target region
• Short treatment time (can be daycare)
• Highly conformal

8. BRACHYTHERAPY - DISADVANTAGES
• Invasive, require anesthesia
• Limited to smaller, well localized tumor
• Difficult to maintain uniformity across
centres
• Labour intensive

9. BRACHYTHERAPY IN CERVIX
• Standard part of locally advanced disease (FIGO IB2 - IVA) following EBRT+CCRT
• Brachytherapy alone: earlier stage disease (IA - IB1).
• Palliative in IVb: Brachy + EBRT

10. CONTRAINDICATIONS
• Prior pelvic RT with brachytherapy
• Life expectancy less than 6 months

11. IS BRACHYTHERAPY NECESSARY?

12. BRACHYTHERAPY HISTORY

14. • Fractionated course of radiotherapy
• 2-3 applications each for 20 to 30 hours
• Intravaginal boxes (lead or gold), intrauterine tube (flexible rubber)
• Unequal loading of the uterine (30-90mg of Ra) and the vaginal (60-80mg Ra)
• Total dose - 6500-7100 mg Ra (4500 mg Ra by the vaginal box)
STOCKHOLM

16. PARIS
• A single application of radium
• Two cork colpostats and an intrauterine tube
• Almost an equal amount of radium was used in the uterus and the vagina
• Intrauterine sources - 3 radioactive sources in the ratio of 1:1:0.5
• Dose of 7000- 8000 mg-hrs of radium over 5 days

17. COMMON FEATURES and PROBLEMS
• Intrauterine tubes separate from vaginal colpostats - loose geometry
• Longest possible uterine tubes were preferred - highest dose to the paracervical
tissue and the pelvic lymph nodes
• EBRT - in absorbed dose and Brachytherapy in Milligram-hours Radium
• Dose prescription in mg-hours Ra ignored the importance of tolerance of OAR’s

18. MANCHESTER – TODD AND MEREDITH
1. Define treatment in terms of dose to a point
• Anatomically comparable from patient to patient
• In a region where dosage is not highly sensitive to small alteration in
applicator position
• In position that allows correlation of dose levels with clinical effects

19. MANCHESTER – TODD AND MEREDITH
2. Design a set of applicators and their loading which would give same dose rate
irrespective of the combination
3. Formulate a set of rules
• Activity
• relationship
• positioning of radium sources
giving rise to desired dose rate

21. POINT A – INDEX OF LIMITING DOSE
1938, Todd F: initial lesion of radiation necrosis was not
due to direct effects on the rectum or the bladder, but
due to high dose effects in the area in the medial edge of
the broad ligament, where the uterine vessels cross the
ureter (paracervical triangle)
Defined a point, which was 2 cm lateral to the center of
the uterine canal and 2 cm superior to the mucosa of the
lateral fornix, in the plane of the uterus

22. POINT A THROUGH HISTORY
• Point Ao (1953): 2 cm above the external os of uterus and 2 cm lateral to uterine
tandem in the plane of uterus
• Point Av (1987): 2 cm lateral to the midpoint of the cervical collar and 2 cm above
the top of the colpostats when measured at the point of their intersection with
the tandem midpoint in a lateral radiograph

23. ABS POINT A

24. RULES SET
• Not more than 1/3rd of total dose to point A should be delivered by the vaginal ovoids
• 1 unit of Ra – 2.5mg of 1mm Pt filtered Ra
• Total Dose to point A: 8000 R
• Total applications: 2
• Total Time for each application: 72 hrs (Total 144 hrs)
• Dose rate desired: 55.5 R per hour to point A

25. POINT B – LATERAL FALLOFF OF DOSE
• Corresponds to location of the obturator nodes
• Around the same level as point A, but 5 cm from the
midline
• Point A can change with geometry of uterus but point B
doesn’t
• Dose to point B:
• depends upon the total amount of radium used
• 4000 mg of radium will give a dose of 1000 R to the
point B in one hour

26. OTHER POINTS
• The recto-vaginal septum:
• 80 % of the dose received by point A
• Packing thickness 15mm
• The vaginal mucosa: Not more than 40% of total dose to point A can be delivered safely
without exceeding the mucosal tolerance
• Point P(Mallinckrodt institute of radiology):
• minimum dose to pelvic lymph nodes
• 6cm from midline in the plane of point A

27. ICRU 38
• Recommended a system of dose specification that
• relates the dose distribution to the target volume
• instead of the dose to the specific point
• The dose is prescribed as a value of an isodose surface that surrounds the target

28. ICRU-38 REPORTING
• Description of the technique
• Total reference air kerma (TRAK)
• Description of the reference volume
• Time dose pattern
• Absorbed dose at reference points

29. REFERENCE VOLUME
• Volume enclosed by reference isodose surface
• 60Gy(EBRT + BT) for classical LDR
• Pear shaped, longest axis coincident with
uterine source
• dH * dT * dW 𝑐𝑚3

30. BLADDER and RECTUM POINT

31. LYMPHATIC TRAPEZOID
On lateral x-ray: line 1 - S1-S2 jn to top of
symphysis and line 2 - middle of this line to the
middle of ant. aspect of L4.
• Mid external iliac (6cm lat. to midline at
inferior end)
• Low para-aortic (2cm lat. to midline at L4)
• Low common iliac (midpoint of line
connecting these two points)

32. PELVIC WALL REFERENCE POINTS
• Represent absorbed dose to
• distal parametrium and
• obturator nodes

34. ICRU 38 ICRU 89
• 2D treatment planning
• reference volume
• Absorbed dose to
 Point A
 Point B
 bladder Points
 rectal points,
 pelvic wall,
 lymphatic trapezoid
• 3D volume based Brachytherapy
• Adaptive Target Concept
• DVH based optimization
• Dose volume,
• Dose point parameters
• Diversification of treatment
34

35. TARGET DOSE SPECIFICATION FOR GTV, HR-CTV & IR-CTV
• Minimum target dose - D100 & D90 :
Minimum dose delivered to 100% & 90% of target, respectively
Uses:
 D100 and D90: Both are highly recommended for reporting
Limitations
• D100:
 Extremely sensitive to inaccuracies in contouring & dose calculation.
 Due to the steep dose gradient, small spikes in the contour causes large deviations in
D100.
• D90
 less sensitive to these influences
 more stable parameter
35

37. Recommended DosePrescription
OAR
D2cc bladder “90Gy EQD2
D2cc rectum “70-75Gy EQD2
D2cc sigmoid“70-75Gy EQD2
TARGET
HDR:
cumulativedose from EBRT & BT
HR-CTV dose:EQD2=85-90 Gy
The IR-CTVdose: EQD2= 60 Gy
Target coverageD90 should be
equal to 100 % prescribed dose
37

38. ISBT SYSTEMS
• Patterson–Parker (Manchester) system
• Quimby (Memorial) system
• Paris system
• Stepping source dosimetry

39. APPLICATORS
• A tandem inserted into uterus
• Of different lengths
• Of varying angles (0,15,30,45)
• Ovoids in vaginal fornices abutting the cervix

40. IDEAL APPLICATOR
• Rigid material - fixed geometry
• Light weight – patient comfort
• Inert material and easy sterilization
• Minimal attenuation – no own characteristic radiation

41. APPLICATOR SELECTION
• Thorough pelvic examination and MRI
• Extent of residual disease
• Vaginal capacity
• H/o surgery (intact uterus)

42. INTRACAVITARY BT
• no residual disease
• residual disease at the cervix
• limited to the medial parametrium and/or upper vagina
• Placement of applicator in uterine and vaginal cavities in the vicinity of target
tissues (residual disease, uterus, parametrium, adjacent vaginal mucosa)

43. TANDEM - OVOID/FLETCHER SUIT - ICBT
• Central tandem and 2 colpostats
• Various angles of central tandems and various sizes of
colpostats
• Semi-fixed applicator (stainless steel or CT/MR
compatible acrylic)
• Designed to deliver adequate doses to uterus/cervix,
upper vagina (2-2.5 cm) and medial parametrium by a
standard pear-shaped dose distribution

44. TANDEM AND RING - ICBT
• In shallow fornices
• Fixed geometry (stainless steel or CT/MRI compatible)
• Similar dose distribution properties as TO applicator
• Ring provides an additional degree of freedom to load
the vaginal sources over the ovoids
• Poor lateral throw-off of dose

45. TANDEM WITH VAGINAL CYLINDERS – ICBT
• Upper vaginal stenosis or narrowing
• Superficial lower vaginal disease
• The dose distribution is cylindrical
• Single source channel - lateral throw off of dose is lesser
than ovoids/ring

46. IC+IS BT
• Recommended if the residual disease at cervix extends into the parametrium beyond the medial
third at the time of BT
• Insertion of interstitial needles/tubes in addition to the standard ICBT procedure
• Through array of holes in ovoids/ring
• into medial parametrium, in parallel direction
• into the lateral parametrium additional oblique needles/tubes

47. VIENNA – TR WITH NEEDLES
• MRI compatible tandem with ring with an array of holes for
insertion of needles/tubes into the medial parametrium
• Template at the level of the vaginal fornices to insert
needles/tubes into the parametrium
• Needles improve the lateral dose throw off by another 1.5 cm
to treat additional parametrium

48. TO + NEEDLES (UTRECHT)
• Similar principles as the Vienna applicator
• Has holes in the ovoids to insert needles into the
parametrium to improve coverage beyond point A

49. VENEZIA APPLICATOR - IC+IS
• Central tandem
• Ovoids/two ring halves - accommodate straight or
diverging parametrial needles
• Detachable perineal template
• Treatment of lateral parametrium - modified ovoid/ring
• Lower vagina or paracolpos - perineal template

50. INTERSTITIAL BT
• Large lesions
• Lateral parametrium involvement
• Lower vaginal disease
• Os not negotiable
• Vault disease

51. SYED-NEBLETT GYN TEMPLATE
• Perineal template with provision for central
vaginal cylinder and tandem when required
• Array of holes to insert needles/tubes through
the perineum in a butterfly shaped positions

52. MARTINEZ UNIVERSAL PERINEAL INTERSTITIAL
TEMPLATE (MUPIT)
• Acrylic perineal template with array of holes for
straight and divergent needles, and the cylindrical
obturator
• Number of needles, depth of insertion, angle and
positions of needles determine the dose
distribution characteristics
• The needles can be secured for individual
movements with the help of screws and a
reinforcement plate

53. ICBT STEPS – before table
• Pre-evaluation (clinical and MRI)
• Informed consent
• Part preparation
• Bowel preparation

54. ISBT STEPS – before table
• Pre-evaluation (clinical and MRI)
• Pre-anesthetic checkup
• Informed consent
• Part preparation
• Bowel preparation (enema and peglec)

55. ICBT/ISBT STEPS – on table
• Anesthesia or sedation
• Lithotomy position
• Painting and draping
• Urinary catheterization with 7cc (radiopaque contrast if radiograph-based or air/normal saline if
CT/MRI-based) in bulb
• Catheter pulled down so balloon rests against the bladder trigone

56. ICBT STEPS – on table
• Examination under anesthesia
• Uterine sound - dilate os, uterus length, anteverted or retroverted
• USG – guided(avoid perforation) insertion of tandem of appropriate length and angle
• Optimum ovoid or ring size
• Adequate vaginal packing (ant. and post. )
• Superiorly to push bladder and rectum away
• Inferiorly to stabilize geometry
• T-bandage to secure applicator

58. ISBT STEPS – on table
• Examination under anesthesia
• Length of vagina determined using obturator
• With obturator in vagina and template against perineum, stainless steel needles with a trocar tip
(18-20 cm length) are inserted through the perineum into the desired target adequately using an
array of holes over the template
• Number and position of needles are according to stipulated depth under DRE with or without
TRUS guidance

59. ISBT STEPS – on table
• All the needles are secured in between the two plates with fixation screws
• Template assembly fixed to perineal skin by stitches at the four corners
• Adequate intra- and postoperative analgesia should be considered
• T-bandage to secure applicator

61. ICBT/ISBT STEPS – after table
• Patient shifted for simulation (2D/3D)
• MRI – gold standard
• Delineates sigmoid
• Delineates cervix from uterus
• Better CTV and parametrial visualization
• But Costly

62. IDEAL APPLICATION
• Longest tandem (increases point B dose)
• Largest ovoid (vaginal surface dose falls by 35% and more
lateral throw-off) possible
• Tandem at 1/3rd between S1-S2 and symphysis and bisect
the ovoids in both AP and lateral X-rays
• Bladder and rectum should be packed away

63. IDEAL APPLICATION
• Ovoids should fill the vaginal fornices
• Ovoids should be 5-10mm apart to accommodate flange
of tandem
• Flange of tandem should be opposed to cervix
• Tandem should be as nearly as possible in midline in AP
radiograph equidistant from lateral pelvic wall

64. RTOG 0116 AND 0128

66. Clinical Target volume
Adaptive CTV-T (CTV-Tadapt):
• After any treatment phase
 GTV-Tres
 the residual pathologic tissue that might
surround the residual GTV-T.
CTV for the Primary Tumor (CTV-T).
 GTV-Tinit and a
 volume of surrounding
tissue
(the risk of microscopic
disease is deemed so high
that this region should be
treated with a dose sufficient
to control microscopic
disease)
CTV-T HR CTV-T IR CTV-T LR
• GTV-Tres,
• whole cervix
• Adjacent residual
pathologic tissue
• GTV-Tinit as
superimposed
on the topography at the
time of brachytherapy,
• margin surrounding
the
anatomical cervix border
• compartments at
risk for potential
contiguous or non-
contiguous
microscopic
spread from the
primary tumor
66

67. The residual (extra-cervical)
pathologic tissue is defined as one or
more of the following:
† residual visible mucosal change;
† pathologic induration;
† residual gray zones (MRI);
† any other residual pathologic tissue
on MRI orclinical examination
67

68. IR-CTV
Limited disease Extensive disease
• HR-CTV + safety margins
 5 mm AP limited by bladder or rectum
 10 mm cranially into uterine corpus
 10 mm caudally below the cervical os
into the vagina.
 10 mm laterally into both parametria,
(representing internal third)
• GTV-D superimposed on HR-CTV at time of BT
(GTV-BT + Cervix + extracervical tissue) taking
original anatomical tumour spread as reference.
• Margins are added depending on the regression in
initial tumor extent present at diagnosis
68

69. Complete remission Partial response Stable disease
IRCTV = HRCTV + GTV diagnosis +
safety margin 10 mm to the initial
tumor extension at diagnosis
IRCTV = HRCTV +GTV diagnosis +
Safety margin of minimum 10 mm
added into the direction of potential
spread (parametria, vagina, uterus)
IR-CTV = HR-CTV + GTV-diagnosis
Without any safety margins
Extensive Disease
69

70. ISBT PLANNING
• CT imaging is usually performed for template-based interstitial BT planning
• MRI-based (if MR-compatible applicator)
• Planning is primarily based on basic Paris system rules including
• defining basal dose (BD) points
• normalization to these points
• prescription to the reference isodose (e.g. 85% of basal dose)
• However, with the use of a stepping source dosimetry system, the plan is further
optimized using geometric followed by manual optimization

71. DOSE SPECIFICATION
• Point A as per ICRU and ABS
• Volume based

73. TREATMENT
• Application reconstruction
• Source loading pattern, planning and optimization(how long the source dwells at
each possible dwell position)
• Plan evaluation and documentation of DVH parameters
• Dose and fractionation
• Patient treated and deloaded

74. DOSE PRESCRIPTION
• Equivalent dose at 2 Gy per fraction (EQD2) assuming α/β of 10 Gy for tumor and 3 Gy for OARs
• Minimum dose of 75 Gy (range: 75-85 Gy) EQD2 to point A depending on the stage, or a minimum
dose of 85 Gy (range: 85-90 Gy) EQD2 to target (CTVHR D90) should be delivered
• Dose constraints:
• ICRU bladder point – 95Gy
• ICRU recto-vaginal point - 65-70 Gy
• 3D planning: 2 cm3 doses for bladder and rectum - less than 95 Gy and 75 Gy, respectively

75. DOSE PRESCRIPTION
• Fractionation regimens range from 5 to 9 Gy per fraction prescribed at either point A or to the
CTVHR (D90) at 1-2 fractions every week for a total of 2-6 fractions
• Recommended to limit the dose per fraction to less than or equal to 7 Gy
• Respect the overall treatment time (OTT) of less than 56 days

76. REPORTING – MINIMUM STANDARDS

77. COMPLICATIONS
• Perforation
• Vaginal injury
• Bleeding
• Bowel, rectal and bladder injuries

78. HDR over LDR
• Eliminates RT exposure for caregivers
• Shorter treatment time
• Patient comfort
• Geometry maintained
• OPD procedure
• Treat large number of patients
• Smaller diameter sources
• Reduces need for GA and dilatation
• Allows integration of EBRT and BT – shorter overall treatment time and better tumour control

79. HDR DISADVANTAGES
• Radiobiology – worse therapeutic ratio – fractionation helps
• Costly
• Error hazard

80. RADIOBIOLOGY – HDR vs LDR

81. WHY IRIDIUM?
• Ir-192, half life 73.83 days
• Average gamma energy 0.380 MeV – less shielding
• High specific activity, 450 Ci/g
• Seeds, pellet and strands of nylon ribbon
• HDR source, 10 Ci, source replacement 3-4 months

82. VAGINAL CUFF BT (SORBO)
• Vaginal cylinder (if total hysterectomy)
• Tandem with cylinder (if supracervical hysterectomy)
• 3-5cm prox vagina treated (whole length if only
papillary serous/clear cell/ grade 3 disease/
extensive LVI)
• Prescription at 5mm from vaginal surface (95% of
lymphatics within 3mm)

84. THANK YOU