Brachy Mesh Implants for Lung Cancer

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Brachy MeshImplants for Lung Cancer

• Cindy Thomason
• Aurora HealthCare Metro

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Brachy Mesh Implants

• I-125 seeds sewn in mesh in a grid layout
• Indications
• Stage I nonsmall cell lung cancer
• Metastases

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125I, Model 6711

• Emitted radiation 26 - 35.4 keV photons
• HVL 2.0 cm tissue, 0.025 cm lead
• T ½ 60 days
• Seeds are 4.5 mm long, 0.8 mm diameter

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125I Brachy Mesh

• Basis is a Vicryl mesh which is a flexible,
  absorbable mesh
• Tensile strength of mesh is 10 is 6 weeks
• 125I seeds in suture are embedded in mesh in grid
  array
• Size and spacing of array decided by Radiation
  Oncologist and Thoracic Surgeon

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125I Brachy Mesh

• Typical size / spacing
• 4 rows x 10 seeds/row, 1cm spacing between seeds
  and rows
• Ave activity / seed 0.41 mCi
• Ave total activity 16.5 mCi

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125I Brachy Mesh

• Used for patients with lung cancer or mets having
  a sublobar resection
• Mesh laid over
• staple line and
• sutured in place

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125I Brachy Mesh

• Most procedures can be done via minimally
  invasive surgery

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125I Brachy Mesh

• No adverse effects (e.g., loss of pulmonary
  function, radiation induced pneumonitis) related
  to placement of mesh have been seen
• Similar length of
• hospital stay and
• incidence of post-
• operative
• complications to
• resection alone

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125I Brachy Mesh

• 110 patients
• median 11 month follow-up
• (range of 1-68 months)
• significant improvement
• in local recurrence
• 19 with sublobar alone
• vs
• 1 with sublobar resection brachytherapy

Voynov, et al., Brachytherapy 4278-285,
2005 Stantos, et al., Surgery 134691-697, 2003
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Dose Prescription

• 120 / 100 Gy to a point 0.5 cm above / below
  plane of implant with margin of 1-2 cm along each
  side of the resection staple line
• 100 Gy used for patients with previous external
  beam treatment or tumor location near heart,
  aorta or spinal cord
• We use 100 Gy because of difficulty in predicting
  location of staple line / mesh

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Treatment planning

• Johnson, et. al. (PMB 521237-1245, 2007)
  prescribed to point average of peak over row and
  trough between rows
• We chose to also average in points between seeds
  ?Therefore, we created our own nomogram for
  standard configurations and spacing
• Spacing between rows and seeds can be modified to
  adjust for seed activity availability

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Treatment Planning

• BrachyVision commissioned for I-125 Model 6711
• Compared to hand calculation and Johnson, et.al.
• Agreement with Johnson, et.al. to within 5
  reasonable due to differences in prescription
  point and uncertainty in parameters used in
  publication

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• Pre implant dosimetry based on nomogram generated
  in house
• Prescription based solely on preimplant geometry
  of mesh, not patient anatomy

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Estimated Personnel Exposure from Brachy Mesh
Procedure

• Thoracic Surgeon will receive greatest exposure
• Estimated hand dose 2.5 mrem
• Estimate
• 5 mrem / procedure x 50 procedures / year
• ? 250 mrem / year
• This is less than 10 of the dose limit, 5000
  mrem / yr
• Therefore, film or ring badges are not necessary
  for any personnel

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Regulatory Requirements for Release of Brachy
Mesh Patients

• Brachy Mesh patients can be released to general
  public if the exposure rate at 1 m from patient
  is
• 1 mrem / hr or less (WI HS 157, Appendix U,
  Table 15)
• Expected exposure rate from patient is 0.6 mrem
  / hr

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• For 1st 29 patients
• Exposure range 0.05 0.95 mR/hr
• Average exposure rate 0.42 mR/hr
• ( 0.13 mR/hr (energy corrected))
• Brachy Mesh patient could be
• released into general population as
• soon as procedure is completed

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OR Procedures

• Handled similarly to a prostate implant
• Seed count performed prior to patient leaving OR
• Personnel and surroundings surveyed

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Radiation Safety Procedures for Dislodged
Radioactive Source

• Patients in-house 1- 5 days
• Since 125I sources are embedded in Vicryl mesh,
  it is very unlikely that a source will be
  dislodged
• However, all patients leave surgery with a chest
  tube and atrium
• ? only potential route for 125I seed to exit
  body provided

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• Surveys performed
• When atrium replaced
• When chest tube replaced
• When chest tube and
• atrium removed

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Posting

• Minimal since patient could be released
  immediately
• Posting on front of chart and patient room door
  to save chest tube or atrium if changed and to
  call physics for survey
• Physics posts release notice after survey
  completed

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Brachy Mesh Patient Radiation Safety Instruction

• For 3 months, avoid prolonged contact with
  pregnant women or children at distances closer
  than 3 feet no limitations at distances greater
  than 3 feet
• Patients are given wallet card with implant
  information and facility information and made
  aware of increased security and monitoring for
  radioactivity

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Challenges

• Some (3) patients have received two Brachy Mesh
  implants
• Request a minimum of 1 month between implants
• Exposure rates for second implant have been
  comparable or less than for first implant

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Challenges (cont.)

• Patients with defibrillators or pacemakers
• Move device
• Perform worse case estimate of minimum allowed
  distance
• Complicated by difficulty in estimating distance
  between mesh and device prior to implant

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Challenges (cont.)

• Patients with malignant effusion
• Treatment consists of placing a pleural catheter
  for sporadic drainage, potentially long term
• First issue - exposure to personnel performing
  procedure
• Second issue - seed migration into drainage fluid
• As mesh dissolves, fibrosis forming around seeds
  helps to keep them in place
• Treat drainage fluid similarly to urine from
  prostate implant patients

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• Post planning?

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In conclusion

• After start-up process, Brachy Mesh implants are
  a relatively simple procedure for the staff with
  essentially no side effects for the patient
• Early results show improved survival which
  hopefully will be reinforced as more data becomes
  available