Intensity modulated radiotherapy followed by robotic radiosurgery boost in early head and neck cancers: a dosimetric study

1. Intensity modulated radiotherapy followed by
robotic radiosurgery boost in early head and
neck cancers: a dosimetric study
Debnarayan Dutta*, MD; Mahadev P * MD, DNB;
Sudhakar, MSc # ; V Murali# PhD; PG Kurup# PhD
*Department of Radiation Oncology, #Medical Physics,
Apollo Speciality Hospital, Chennai, INDIA

2. Background
- Majority of the early head & neck cancer is treated with EBRT
- RT given to primary tumour and involved nodes treated with higher dose (66-70 Gy)
- Uninvolved neck nodes receive lower dose (60-54 Gy)
- Common complication of EBRT is xerostomia
- Severity of xerostomia is dose dependent
- HDR brachytherapy boost or fractionated radiosurgery is an option to reduce dose
to salivary gland

3. Methodology
Node negative H& N cancer (Ca Tonsil) (T3 N0M0)
IMRT treatment planned
PTV66Gy: 66Gy/30#
Primary tumour
PTV60Gy: 60Gy/30#
Bilateral level IB,II LN
PTV 54Gy/30#
Bilateral III,IV LN
Plan evaluation:
Target coverage
OAR dose (Spine, Parotid)
(n=1)

4. Standard IMRT plan: Dosimetry
Node negative H& N cancer (Ca Tonsil) (T3 N0M0)
IMRT: 66Gy/30#
Dose (Gy)
Max Min Mean
PTV66 70 63.9 67.3
Spinal cord 35.5 - -
Ipsilateral parotid 50 12.8 26.4
Contralateral parotid 43 11.7 20
Larynx 62.4 32.1 44.6
Mandible 64.4 24.5 48.5
Lips 37.4 20.3 27.5

5. Dryness of mouth related QOL
Higher scores indicate poorer QOL Score
Jabbari et al IJROBP 2005

6. Grade II/IV xerostomia at follow up Decrease in salivary flow at follow up
Kam et al, JCO 2007
Xerostomia evaluation
Subjective assessment Objective assessment

7. Dose vs salivary function with time
Unsimulated salivary flow after IMRT Simulated salivary flow after IMRT
More deterioration of salivary function with higher dose
Li et al, IJROBP 2007

8. Methodology to reduce dose to parotids
A) IMRT plans with more precise dose delivery system: eg Tomotherapy, Rapid ARC
B) Conformal radiation therapy followed by HDR brachytherapy boost
C) Conformal radiation therapy followed by fractionated radiosurgery boost: eg CyberKnife

9. Dosimetric study
Node negative H& N cancer (Ca Tonsil) (T3 N0M0)
IMRT: 46 Gy/23#
PTV: Primary+ Level I-IV bilateral LN
IMRT boost: 24 Gy/6#
PTV: Primary
HDR brachy: 24 Gy/6#
PTV: Primary
CK boost: 24 Gy/6#
PTV: Primary
Comparison between boost plans:
1) Target Coverage
2) OAR dose (spinal cord & parotid dose)
(n=1)

10. Plan: IMRT boost (24Gy/6#)
(n=1)

11. Dosimetry: IMRT boost (24Gy/6#)
Dose (Gy)
Max Min Mean
PTV 28.5 22.1 26.3
Spinal cord 7.4 - -
Ipsilateral parotid 10.4 5.9 8.3
Contralateral parotid 4.7 1.8 3.7
Larynx 0.5 0.18 0.3
Mandible 1.9 4.9 10.7
Lips 8.1 3.4 5.6

12. Plan: HDR brachytherapy (24Gy/6#)

13. Dosimetry: HDR brachytherapy
Dose (Gy)
Max Min Mean
Spinal cord 1.2 - -
Ipsilateral parotid - - 3.1
Contralateral parotid - - 1.4

14. Plan: CK boost (24Gy/6#)

15. Dosimetry: CK boost (24Gy/6#)
Dose (Gy)
Max Min Mean
Spinal cord 1.5 - -
Ipsilateral parotid 4.7 0.6 2.1
Contralateral parotid 2.6 0.8 1.7

16. Comparison of three plans
IMRT boost HDR boost CK boost
Spinal cord Dmax (Gy) 7.4 1.2 1.5
Ipsi-lateral parotid
Mean dose (Gy)
8.3 3.1 2.1
Conta-lateral parotid
Mean dose (Gy)
3.7 1.4 1.7
No significant difference in maximum spinal cord dose and mean
parotid doses between HDR & CK boost plans
In IMRT plan, higher ipsi-lateral parotid dose
(n=1)

17. Comparison of three boost technology
IMRT boost HDR boost CK boost
Technology Widely used Commonly used Not commonly used
Non-invasive Invasive Non-invasive
High dose region Not important High Not important
Low dose region Highest lowest low
Expertise Commonly used Skill important Required
Risk less Risk of arterial perforation
/ anesthetic hazards
less
Patient comfort high Low highest
Patient acceptability High low High
HDR brachytherapy requires high skill, but associated with hazards & high patient discomfort
CK boost requires expertise, highly conformal treatment, patient friendly, but less data available

18. Dosimetric comparison between different modality
(n=85)
Teguh et al. IJROBP 2008

19. Dysphagia related QOL
Poor swallowing function score after boost treatment with
different modality
H&N35
Swallowing
PSS
Normalcy in diet
MDADI
Total
Brachytherapy
(n=42)
7% 21% 14%
CyberKnife
(n=6)
17% 33% 17%
Conformal RT
(n=12)
42% 58% 58%
Preserved swallowing function with brachytherapy & CK boost
CK is an non-invasive option for boost treatment
Teguh et al. IJROBP 2008

20. Author Study n Pt criteria Modality Treatment Results
Chang
(1999)
Func
Neurosurg
23 Nasopharynx
with skull base
involved
SRS boost EBRT followed by
SRS boost (12Gy)
Excellent tolerance
Good local control
36% had distant mets
Hara
(2008)
IJROBP 82 Nasopharynx SBRT SRS boost: 7-15 Gy 5 yr LC: 98%
5 yr OS: 67%
Chen
(2006)
IJROBP 64 Nasopharynx CK CK boost: 12-15 Gy 3 yr LC: 93%
Le
(2003)
IJROBP 45 Nasopharynx SBRT Boost: 12-15 Gy 3 yr LC: 100%
3 yr OS: 75%
SBRT boost in Nasopharynx
CK: CyberKnife
SBRT: Stereotactic body radiotherapy

21. Author Study n Pt criteria Modality Treatment Results
Heron
(2008)
IJROBP 25 Oropharyngeal
cancer
Re-RT
SBRT RT dose escalation
study
Max dose 44 Gy
Low toxicity with SBRT
4 pt CR
12 pt Stable disease
Teguh
(2008)
IJROBP 132 Oropharyngeal
Nasopharyngeal
Brachy
CK
EBRT followed by
boost with
brachytherapy, IMRT
or CK
Dose to constricters
least with brachytherapy
Swallowing function
preserved with brachy &
CK
Won
(2009)
IJROBP 36 Recurrent
H&N Ca
CK CK : 30Gy/5# CR 43%
Gr III toxicity 13 pt
Voynov
(2003)
Tech
Cancer Res
Treat
22 Rec H&N cancer CK CK: 20-30Gy/5# 2yr LC: 26%
2 yr OS: 22%
SBRT in H & N cancer
CK: CyberKnife
SBRT: Stereotactic body radiotherapy

22. Conclusions
• rRS boost is feasible option for boost treatment in early node negative
head and neck cancer.
• Patients with medical contraindications to surgery or not suitable for
brachytherapy may be candidate for such treatment.
• Prospective studies are required for assessment of efficacy, patient
acceptance and quality of life.