This document discusses optimization techniques for radiotherapy in treating childhood medulloblastoma. It reviews conventional radiotherapy, intensity-modulated radiotherapy (IMRT), and proton therapy. The major side effect of treatment is ototoxicity or hearing loss. Studies show proton therapy significantly reduces ototoxicity compared to IMRT or conventional radiotherapy. While all techniques are effective when combined with chemotherapy like cisplatin, proton therapy allows for best sparing of healthy tissue and lowest toxicity rates. The goal is optimizing treatment to cure medulloblastoma while minimizing negative effects on patients' quality of life.

2.  Introduction
 Statement of Problem
 Materials and Methods
 Results and Discussion
 Summary of Findings
 Conclusion
 References
2

3.  Cancer is the second most common
cause of deaths in children in the US
(IARC, 2016).
 In Nigeria, cancer contributes 3.3% of
child deaths. (F. Abdulkareem, 2009)
 Survival rates increased from
20% to 70% from the 1970’s to date.
(IARC, 2016).
3

4. 4

5. 5
Fig. 1: Most common childhood cancers

6. 6
Genetic, 10%
Environment
Exposures…
Unknown,
82.5%
Source: Birch (1999) and Lichtenstein (2000)
Fig. 2: Causes of paediatric cancers

7.  As survival rates have increased, there is
now increasing concern about the quality
of the child’s life after treatment.
 There is therefore need to optimize
radiotherapy technique to minimize
Sequelae and other non-desirable effects
of radiation.
7

8.  To optimize radiotherapy techniques in
children, maximize cure rate and minimize
negative effects.
 To review different optimization radiotherapy
techniques in treatment of child
medulloblastoma.
 To compare the different techniques
8

9.  Higher toxicity:
Significant normal tissue injury, even at
low doses for children.
 Radiosensitivity:
Children are more sensitive to radiation by
a factor of 10 to 15 compared to adults
(BEIR VII Report, 2006).
9

10. 10
[Source: IAEA, 2017 ]
Fig. 3: Graph showing risk of cancer induction
as a function of age

11.  Longer Life Expectancy
Children live long enough for induction of
secondary cancers and late effects. E.g.
thrombosis, fibrosis, etc.
 Immobilization:
Conscious sedation may be required to avoid
movement during radiotherapy (XRT).
 Late presentation, esp. in developing world:
Treatment is less effective with late presentation.
11

12.  Some childhood cancers are best treated
by combination therapy: surgery,
radiotherapy and chemotherapy.
 This reduces the dose, intensity and
irradiated volume, and keeps side effects
as low as possible while achieving a high
cure rate.
12

13.  Medulloblastoma is the most common
malignant CNS tumour in children.
 It originates from the cerebellum and
grows into the 4th ventricle.
 It can metastasize to the spinal column
via the Cerebrospinal Fluid (CSF).
13

14. 14
Fig 5: Sagittal view of brain
{Source: American Society of Clinical Oncology, 2004}
Cerebellum, pons and medulla oblongta form
the POSTERIOR FOSSA.

15. 15
Healthy Brain Brain with Medulloblastoma
Fig 6: Showing healthy child brain (L) MRI and
4 year old child with medulloblastoma
{Source: blueskyethinking.org}

16.  Conventional XRT: 2 parallel-opposed
lateral beams whole brain irradiation
(WBI), and spine.
 Total Dose: 54 – 56 Gy (in 1.8 Gy fractions)
 Treatment boosted by chemotherapy, esp.
cisplatin.
 Craniospinal irradiation (CSI) is the
cornerstone of medulloblastoma XRT.
16

17. 17

18. 18

19.  Ototoxicity
› Hearing loss
› Due to dose to cochlea and 8th cranial nerve.
 Loss of IQ
 Neurocognitive sequelae (e.g. attention
disorders, slow psychomotor processing)
19

20.  Compared conventional XRT with IMRT.
 Studied 73 children with average-risk
medulloblastoma
 IMRT TECHNIQUE: Delivered 23.4 Gy CSI
followed by a 12.6 Gy conformal boost to
the posterior fossa and then a tumour bed
boost of 19.8 Gy (TOTAL: 55.8 Gy).
 All patients also received high-dose
chemotherapy.
20
HUANG ET AL., (2003)

21.  Compared plans for three (3) methods:
conventional, IMRT and proton therapy.
 Isodose distributions and DVHs were then
compared.
 As a test case, a 3 year old boy was
sedated and scanned. The images were
then transferred to the TPS where the
RoIs were outlined.
21
ST. CLAIR, ET AL., (2004)

22.  Children treated with IMRT received a
significantly lower dose to the cochlea
compared with conventional XRT
(36.7 vs. 54.2 Gy).
 Hearing function after treatment was
graded on a scale of 0 to 4 using pure-
tone audiograms.
22
HUANG ET AL., (2003)

23.  64% of the conventional XRT group developed
grade >=3 ototoxicity
 Only 13% of IMRT group developed
grade >= 3 ototoxicity
 Children treated with IMRT thus
experienced significantly less ototoxicity
than conventionally treated children.
23
HUANG ET AL., (2003)

24.  Substantial normal-tissue sparing was
realized with IMRT and proton therapy.
 Dose to 90% of cochlea was reduced from
101.2% in Conventional XRT to
33.4% in IMRT, and to
2.4% in Proton therapy.
24
ST. CLAIR, ET AL. (2004)

25. 25
{Source: St. Clair, et al (2004)}
Fig: Compares proton therapy with Conventional XRT

26. 26
ST. CLAIR ET AL. (2004)
Fig: Proton therapy shows more healthy tissue sparing than
IMRT {Source: St. Clair, et al (2004)}

27. 27
SPECIFIC OBJECTIVES Summary of Findings
To review different
optimization radiotherapy
techniques in treatment of
child medulloblastoma
1) Conventional, IMRT and Proton
Therapy can be used.
2) Methods are most effective when
combined with chemotherapy,
esp. cisplatin.
To compare the different
techniques
1) Ototoxicity was the major
determinant, measured by
hearing loss.
2) Proton therapy provided the
lowest ototoxicity rates, followed
by IMRT, and then Conventional
XRT

28.  Medulloblastoma is the most common
malignant brain tumour.
 It is best treated with radiotherapy, in
addition to chemotherapy, esp. cisplatin.
 The major side effect is ototoxicity, i.e.
hearing loss.
 Proton therapy offers the best results,
followed by IMRT, then Conventional XRT.
28

29. 1. IAEA (2010). Radiation Biology: A Handbook for
Teachers and Students. Vienna: IAEA.
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DC: National Academy of Sciences, National
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Care: Facing the Global Challenge. Vienna: IAEA
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Biol Phys 2003;52:599–605.
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compared to conventional X-ray or IMRT in the treatment of
pediatric patient with medulloblastoma. Int J Radiat Oncol
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9. IARC (2016) International Incidence of Childhood Cancer.
Retrieved Sept 10, 2010 from http://iicc.iarc.fr.
10. M. Beyzadeoglu, et al., (2010), Basic Radiation Oncology.
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31. To contact, email ekpovictortoday@gmail.com