radiation oncology

1. Dr Mohammad Abu Ashour
Radiation Oncology Resident
Jordanian Royal Medical Services
‫الرحمن‬ ‫هللا‬ ‫بسم‬
‫الرحيم‬

2. CONTENT
 Definition
 Anatomy
 Indication of CSI
 Doses of CSI .
 Technique ( 3D – conformal in supine position )
 Complications
 Rule of CTX in CSI
 Other technique of CSI.

3. Definition
CSI is a technique used in radiation
therapy to deliver a prescribed dose to
the entire cranial-spinal axis .
CSI : treat anywhere CSF flows ( sub
arachnoid space ).

4. History
 The concept of CSI was advanced by Dr Edith Paterson

6. Anatomy

7. Indications
 Medulloblastoma.
 Primitive neuroectodermal tumour.
 Atypical teratoid/rhabdoid tumour.
 Pineoblastoma.
 Epenedymoma with evidence of CSF involvement ,
anaplastic type.
 CNS Germ cell tumor with neuroaxis invlvment .
 Primary CNS lymphoma with leptomeninigeal
involvment

8. What makes CSI challenging ??
 Patient position and immobilization difficult
especially in pediatric cases ( may require
anaesthsia).
 Large , irregular target volume.
 Critical structure with special importance to
pediatric cases who are potential long term
survivor .
 Problem of matching junctions between the fields .

9.  CSI can be done with photon , proton ,3D
conformal IMRT , VMAT or Tomotherapy.
 Every technique has advantages and
disadvantages .
 In this lecture we will focus on the 3D –
conformal in supine position as we use this
technique in our department .

10. Doses of CSI
Average risk Medulloblastoma :
 CSI 23.4 Gy/13 fx with weekly concurrent
vincristine
 Posterior Fossa As per recent ACNS 0331
results, boost I.F (rather than entire PF) to
54–55.8 Gy

11. High risk*
CSI 36 Gy/20 fx with weekly concurrent
vincristine
Boost PF to 54–55.8 Gy**
Post-RT CHT

12.  Primitive neuroectodermal tumour.
 Atypical teratoid/rhabdoid tumour.
 Pineoblastoma.
 , anaplastic Epenedymoma
 Treated as high risk Medulloblastoma

13.  A simple technique for craniospinal radiotherapy
in the supine position
 William A. Parkera,*, Carolyn R. Freemanb
 Department of Medical Physics, and Department of
Radiation Oncology, McGill University Health
Centre, Montreal, Canada

14.  Methods: The patient is CT scanned and treated in the
supine position. The clinical target volume and relevant
critical structures are outlined on a planning CT scan.
 Half beam blocked lateral fields with a collimator rotation
are used to match the beam divergence from the superior
border of the spinal field at the C2 vertebral body.
 The shielding for the cranial fields is generated
automatically, and the dose distribution is calculated using
a 3D treatment planning system.
 The position of the isocenter of the spine field is always a
fixed longitudinal distance from the isocenter of the brain
fields. If multiple posterior fields are required, the
isocenter of the second spine field is always a fixed
longitudinal distance from that of the first.

15.  the gap between the fields is determined
using virtual simulation and feathered
during treatment using the asymmetric jaws
of the linear accelerator.
 this technique requires only longitudinal
couch motions, and is simple to plan and
easy to incorporate into the workload of a
busy radiotherapy department

16. Technique
Positioning
Immobilization
 Simulation
Target and OAR Delineation
Treatment Planning

17. Positioning
Prone Vs supine

18. Prone Position:
 *Advantages :
 Good alignment of the spine
 Direct visualization of the field junctions.
 *Disadvantages :
 Uncomfortable
 Technically difficult to reproduce.
 Difficult anesthetic maneuvers

19. Supine position
 Supine
 More comfortable.
 Better reproducibility
 Safer for general anesthesia
BUT
 Direct visualization of spinal field is not possible

20. Immobilization
Thermoplastic mask for
immobilization of the head.
Alpha cradle
Vac lock

22. Simulation
 CT simulation
 3mm slice thickness
 Simulation from top of the head to below the end of
sacral area with arms down. The neck is
hyperextended so that spine fields do not exit through
the patient’s mouth .
 One iso reference .

23. Target Volume and OAR:
 Entire brain and its meningeal
coverings with the CSF.
 Spinal cord and the leptomeninges
with CSF.

25.  The CSF space around the cribriform plate , optic
nerves are critical and should be included in CTV.
 For the inferior extent of the spine fields, must be
below the bottom of the thecal sac. The thecal sac
can often be seen on both finer cut CT imaging in
soft tissue windows and sagittal MRI imaging.
 The thecal sac typically ends between S1 and S3.
 Nerve roots. The CTV should include the
neuroforamina at all levels of the spine.

29. Treatment Planning
 two parallel opposed lateral cranial fields matched
with the posterior spinal field to cover the entire
length of the spinal cord
 Fixed field parameters are used.
 Since the patient is treated in the supine position, the
posterior fields are difficult to visualize on the patient.
The setup is therefore based on anterior setup fields
with the same isocenters and field dimensions as the
treatment fields.

30. Fields arrangement :

31. Two spinal field

32. Junction shift
 The junctions between the fields are feathered during
the course of treatment by using the asymmetric jaws.
 The jaw defining the inferior limit of the brain fields is
opened by 1 cm every 9 Gy, while the superior limit of
the spinal field abutting the brain fields is decreased
by 1 cm.
 If a second spine field is required, the inferior limit of
the superior field is decreased by 1 cm, and the
superior limit of the inferior field is increased by 1 cm

33. Portal imaging
All fields are imaged on a daily basis
during the first week of treatment, and
once a week (following each junction
change) thereafter. The portal images
are compared to simulation DRRs.

34. Complications
 Acute: Myelosuppression, nausea/vomiting,
diarrhea, fatigue, hairloss, headaches, muffled
hearing.
 Chronic: Neurocognitive, (memory, attention,
behavior, learning), neuroendocrine deficits
(particularly GH deficiency, hypothyroidism,
gonadal dysfunction), impaired soft tissue/bone
growth , Ototoxicity , secondary neoplasm
,cataract.

35. Factors for decline in IQ after CSI
 Factors for decline in IQ after CSI:
 Age <7 yrs (most important)
 Higher dose (36 Gy vs. 23.4 Gy)
 Higher IQ at baseline
 Female sex
 (Ris MD et al., JCO 2001)

36. What is the annual IQ drop after
full PF boost in MB pts younger and
older than 7 yrs? What structure is
most important?
 IQ drop of 5 points/yr if <7 yo and 1 point/yr if >7
yo. The dose to the supratentorial brain (temporal
lobes) is most important.

37. Rule of CTX in CSI
Attempts to reduce CSI dose
and its associated growth and
neurocognitive toxicities have
been facilitated by optimized
CHT regimens.

38. Chemotherapy can also be given for
younger patients in order to delay
RT, as the high toxicity profile for
patients

39.  In standard risk patients several strategies
were used to decrease the craniospinal
radiation (CSI) dose and to increase overall
survival. Deutsch et al. decreased the CSI
dose to 23.4 Gy but in their early report they
observed an increased rate of CNS failure
compared to 36 Gy

40.  Packer et al. combined chemotherapy with
23.4 Gy CSI and reported a 5 year event free
survival rate of 90% Studies conducted by
the International Society of Pediatric
Oncology (SIOP) and the Children’s
Oncology Group supported the use of 23.4–
24 Gy CSI with adjuvant chemotherapy

41. Medulloblastoma in adult
 Brandes, 2007. Low-risk disease given CSI to
36 Gy, then boost PF 18.8 Gy to total 54.8 Gy.
High-risk pts received combination chemo +
RT. PFS and OS at 5 years were 72% and 75%
for all pts.
 We can omit CTX in adult patients .

42. Proton Treatment
 Protons have the distinct advantage of
minimal dose deposition beyond the Bragg
peak. This allows dose to be limited to the
anterior aspect of the vertebral bodies with
minimal dose extending into the more
anterior structures. This should, ideally,
limit late complications of treatment but the
proton treatment is not available in Jordan
and is significantly more expensive.

43. IMRT
Delivery of CSI with IMRT delivers
conformal high doses to the spine and
brain, but low dose radiation is
delivered to a large volume due to the
multiple beam angles.

44. VMAT
 There are some concerns about increased
risk of secondary malignancies in patients
treated receiving craniospinal irradiation
with volumetric arc therapy compared to 3D
conformal therapy

46. Dosimetric comparison of five different
techniques for craniospinal irradiation
across 15 European centers: analysis on
behalf of the SIOPE- BTG
(radiotherapy working group)

47. Purpose:
 Conventional techniques (3D-CRT) for craniospinal
irradiation (CSI) are still widely used . Modern
techniques (IMRT, VMAT, TomoTherapy , proton
pencil beam scanning [PBS]) are applied in a limited
number of centers. For a 14-year-old patient, we aimed
to compare dose distributions of five CSI techniques
applied across Europe and generated according to the
participating institute protocols, therefore
representing daily practice.

48. Results:
 The modern radiotherapy techniques investigated
resulted in superior conformity/homogeneity and
demonstrated a decreased dose to the thyroid,
heart, esophagus and pancreas. Dose reductions of
>10.0 Gy were observed with Proton compared to
modern photon techniques for parotid glands,
thyroid and pancreas.

49. Conclusions:
 The investigated modern radiotherapy techniques
demonstrate superior dosimetric results compared
to 3D-CRT. The lowest mean dose for organs at risk
is obtained with proton therapy. However, for a
large number of organs ranges in mean doses were
wide and overlapping between techniques making
it difficult to recommend one radiotherapy
technique over another.

50.  Thank you