Brachy Mesh treatment for lung cancer, Cindy

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Brachy Mesh
Implants for Lung Cancer
Cindy Thomason
Aurora HealthCare – Metro
Brachy Mesh Implants
• I-125 seeds sewn in mesh in a grid
layout
• Indications
• Stage I nonsmall cell lung cancer
• Metastases
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
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
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
125I
Brachy Mesh
• Used for patients with lung cancer or
mets having a sublobar resection
• Mesh laid over
staple line and
sutured in place
125I
Brachy Mesh
Most procedures can be done via
minimally invasive surgery
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 postoperative
complications to
resection alone
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 4:278-285, 2005
Stantos, et al., Surgery 134:691-697, 2003
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
Treatment planning
• Johnson, et. al. (PMB 52:1237-1245, 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
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
• Pre implant dosimetry based on
nomogram generated in house
• Prescription based solely on
preimplant geometry of mesh, not
patient anatomy
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
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
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
OR Procedures
• Handled similarly to a prostate
implant
• Seed count performed prior to patient
leaving OR
• Personnel and surroundings surveyed
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
• Surveys performed
• When atrium replaced
• When chest tube replaced
• When chest tube and
atrium removed
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
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
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
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
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
Post planning?
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
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