Total Marrow Irradiation with Helical Tomotherapy along the entire Patient

1
Total Marrow Irradiation with Helical Tomotherapy
along the entire Patients Axis a Planning
Technique to Merge Helical Dose Distributions
producing Uniform Dose in the Junction Region

• M. Zeverino, S. Agostinelli, G. Taccini,
• F. Cavagnetto, S. Garelli, M. Gusinu,
• S. Vagge, S. Barra , R. Corvò

National Institute for Cancer Research Genova-
ITALY
2
Outlines

• TMI rationale and its potential over TBI
  treatments
• TMI treatment technical issues
• Patient selection and treatment approach
• The strategy to overcome limits and delivery a
  Full TOMO treatment
• Dose junction manipulation
• Treatment delivery QA

3
Outlines

• TMI rationale and its potential over TBI
  treatments
• TMI treatment technical issues
• Patient selection and treatment approach
• The strategy to overcome limits and delivery a
  Full TOMO treatment
• Dose junction manipulation
• Treatment delivery QA

4
TMI rationale

• Leukemia relapse (LR) cause of failure after
  allogeneic stem cell trasplantation
• LR first cause of death for patient with advanced
  hematologic diseases
• Total Body Irradiation (TBI) dose escalation may
  reduce LR ratio but is associated with higher
  toxicity
• TMI has the potential to fulfill a dose
  escalation protocol and reduce the dose delivered
  to the organs at risks

5
Dose Volume Histograms TBI vs TMI
TBI
TMI
vs.
Typical TBI Dose Volume Histogram

• 9 entries in PubMed for TMI with HT
• Hui SK et al. Feasibility study of helical
  tomotherapy for total body or total marrow
  irradiation. Med Phys. 2005
• Wong JY et al. Image-guided total-marrow
  irradiation using helical tomotherapy in patients
  with multiple myeloma and acute leukemia
  undergoing hematopoietic cell transplantation.
  IJROBP 2009

6
Outlines

• TMI rationale and its potential over TBI
  treatments
• TMI treatment technical issues
• Patient selection and treatment approach
• The strategy to overcome limits and delivery a
  Full TOMO treatment
• Dose junction manipulation
• Treatment delivery QA

7
How to deal with the couch Y limit?

• Maximum couch travel ability of about 160 cm
• Treatment has to be split in two segments
• Upper body TMI (UTMI)
• Lower body TMI (LTMI)
• Two different treatment approaches
• To treat lower limbs with LINAC
• Extended SSD AP/PA technique
• 4 fixed fields (minimum) with at least 2
  junctions in addition
• To treat lower limbs with TOMO
• FFS oriented
• Single junction
• A method for matching fields should be used

8
Outlines

• TMI rationale and its potential over TBI
  treatments
• TMI treatment technical issues
• Patient selection and treatment approach
• The strategy to overcome limits and delivery a
  Full TOMO treatment
• Dose junction manipulation
• Treatment delivery QA

9
Patient selection

• 15 patients (10 M, 5 F) from 07/2009 to 06/2010
• Median age 35 y (range 18 y 55 y)
• 10 patients with acute myeloid leukemia (AML)
• 5 in relapse status
• 5 in second remission
• 5 patients with acute lymphoid leukemia (ALL)
• 3 in relapse status
• 1 in second remission
• 1 in third remission

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Treatment approach _at_ IST TBI TMI
Day 1
Day 2
Day 3
Day 4
time
TBI TMI 14 Gy
TBI 2 Gy (x2)
TBI 2 Gy (x2)
TBI 2 Gy (x2)
TMI 2 Gy (x1)




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Outlines

• TMI rationale and its potential over TBI
  treatments
• TMI treatment technical issues
• Patient selection and treatment approach
• The strategy to overcome limits and delivery a
  Full TOMO treatment
• Dose junction manipulation
• Treatment delivery QA

12
Matching UTMI and LTMI CT data sets
Two CT scans

• Upper body
• HFS oriented (from vertex to knees)
• Lower body
• FFS oriented (lower limbs including knees)

Two CT data sets

• Whole body CT lower body images are mirrored
  and properly matched with upper body images
• Lower limbs CT original images of lower body

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Matching UTMI and LTMITreatment planning
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Twin LTMI plan Generation

• LTMI easy to plan (rounded PTV, no OARs)
• LTMI plan features
• Fixed number (50) of iterations allowed
• No changes of dose constraint during optimization
• Plan saved as protocol
• LTMI protocol was loaded on the whole body CT
  data set providing identity between structures
• tLTMI dose distribution was then calculated with
  the same fixed number of iterations
• DVH comparison to assess dose identity

Method
Evaluation

• Modified ? index (1 dose/ 1 volume)
• Plans are defined twins only if for gt99 of
  points ?lt1

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Full Helical TMI Dose Distribution
Finally UTMI and tLTMI plans can be summed on the
same CT data set
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Outlines

• TMI rationale and its potential over TBI
  treatments
• TMI treatment technical issues
• Patient selection and treatment approach
• The strategy to overcome limits and delivery a
  Full TOMO treatment
• Dose junction manipulation
• Treatment delivery QA

17
Producing uniform dose in the junction region

• A couple of transition volumes were used to
  improve dose uniformity in the abutment region
  for UTMI, LTMI and tLTMI plans by replacing the
  PTV segments
• PTV Stop replaced the last two segments for UTMI
  and the first two segments for LTMI
• PTV Trans replaced the two PTV segments preceding
  and following PTV Stop for UTMI and LTMI,
  respectively

• Optimization tips
• PTVStop is a RAR (zero dose requested)
• PTVTrans is a PTV (acting as a dose modulator)

LTMI
UTMI
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Junction dose evaluation

• Overall 3D dose distribution allows to evaluate
  calculated dose in the abutment region by means
  of

DVH
Dose profile
Our policy allows maximum dose inhomogeneity of
10 of prescribed dose. Otherwise LTMI is
replanned acting on the dose constraints of both
PTVStop and PTVTrans
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Junction Dose EvaluationTomo vs Linac
LINAC
TOMO

• Full TOMO TMI features
• Easy to deliver (quick setup, no patient shifts)
• More conformal (sparing of lower limbs vessels)

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Junction Dose EvaluationTomo vs Linac
LINAC
TOMO

• Full TOMO TMI features
• Easy to deliver (quick setup, no patient shifts)
• More conformal (sparing of lower limbs vessels)

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Junction Dose HomogeneityTomo vs Linac
Full TOMO junction - 2 Dmin 8 Dmax
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Junction Dose HomogeneityTomo vs Linac
TOMO Linac junction (NO GAP) - 14 Dmin 10
Dmax
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Junction Dose HomogeneityTomo vs Linac
TOMO Linac junction (5 mm GAP) - 28 Dmin 3
Dmax
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Junction Dose HomogeneityTomo vs Linac
TOMO Linac junction (5 mm OVERLAP) - 10
Dmin 34 Dmax
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Junction Dose HomogeneityTomo vs Linac
Junction Dmin ( of target dose) Dmax ( of target dose) Dose Inhomogeneity
Full TOMO -2 8 10
TOMO Linac (NO GAP) -14 10 24
TOMO Linac (5 mm GAP) -28 3 31
TOMO Linac (5 mm OVERLAP) -10 34 44

1. Inverse planning allows to obtain a more uniform
   dose distribution in the overlapping area
2. Target over- or under-dosage can be easily
   avoided
3. These are calculated values!
4. MV/kVCT registration process will affect dose
   uniformity in the overlapping area

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Junction Dose Homogeneityresults
Structure Mean D5 (cGy) Mean D95 (cGy) Dmean (cGy) HI
PTV STOP 211 (201 218) 194 (189 201) 203 (196 210) 0.08 (0.05 0.13)
PTV TRANS 212 (203 218) 187 (182 191) 200 (195 209) 0.13 (0.07 0.18)
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Outlines

• TMI rationale and its potential over TBI
  treatments
• TMI treatment technical issues
• Patient selection and treatment approach
• The strategy to overcome limits and delivery a
  Full TOMO treatment
• Dose junction manipulation
• Treatment delivery QA

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Plan Verification

• Dose point verification
• A1SL ion chamber Cheese Phantom
• Target sites (i.e. bone marrow)
• 3 ?D
• 2D dose verification
• GafChromic EBT/EBT2
• Anthropomorphic phantom (head and chest)
• Lung equivalent tissue slabs
• ? (3/3mm)

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MV-kV REGISTRATION

• Results from the first 8 treated patients
• Treatment setup (TS) Observed Shift Averaged
  Shift lt 4 mm
• If 4 mm lt TS lt 6 mm, physician review and
  evaluation
• If TS gt 6 mm, patient repositioning

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In vivo dosimetry
In vivo dosimetry assessing the accuracy of
dose delivered in the field junction

• Gafchromic EBT2
• Two stripes of approximately 10 cm long and 2 cm
  wide
• Placed on the skin according to the tattoo
  individuating the junction

MOSFET 5 detectors placed on the skin 1 cm apart
in the long direction according to the tattoo
individuating the junction
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Some numbers
Organ Median Dose reduction Standard Deviation
Brain 45,5 4,6
Left Parotid 30,3 11,5
Right Parotid 29,6 10,3
Oral Mucosa 35,8 9,2
Larynx 56,4 4,9
Thyroid 43,3 9,6
Left Lung 44,3 2,7
Right Lung 47,5 4,3
Heart 45,1 2,1
Liver 47,0 4,1
Left Kidney 56,8 5,2
Right Kidney 60,5 2,1
Bowel 52,2 3,4
Male Gonads 80,7 12,3
PTV PTV PTV
Value Mean () Range ()
D95 93,3 91,9 - 94,2
D90 95,7 94,1 - 96,7
D5 102,9 101,7 - 103,8

• Legenda
• D95 dose received by 95 of PTV volume
• D90 dose received by 90 of PTV volume
• D5 dose received by 5 of PTV volume

MF Time (min)
UTMI (FW 5 pitch 0.287) UTMI (FW 5 pitch 0.287)
mean 1,49 20,5
range 1,33- 1,83 17,5 - 23,5
LTMI (FW 5 pitch 0.287) LTMI (FW 5 pitch 0.287)
mean 1,8 9,0
range 1,73 - 2,00 6,1 - 12,6

• Considerations
• Organ sparing is achievable in terms of median
  dose reduction (i.e. dose delivered to 50 of
  organ volume)
• Small organs are penalized because of technical
  parameters of treatment
• Optimal PTV coverage and homogeneity
• Mean overall beam-on time lt 30 min

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Remarks and conclusions

• Full helical dose distribution is true as long as
  dose identity between LTMI and tLTMI exists
• Different solutions can be adopted for producing
  uniform dose in the junction through inverse
  planning
• In vivo dosimetry is mandatory to assess the
  dosimetric impact of the patient shifts on the
  junction
• Patient alignment process may cause over- or
  under-dosage to PTV. Split the treatment at the
  knees ( lack of bone marrow)
• On a total of 17 patients underwent TMI with HT
  (first patient July 2009), 11 were treated using
  the presented technique
• Treatments well tolerated (1 severe nausea
  episode)
• Short median FU (7 months) . 12/17 patients are
  currently alive in CR