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

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

Methodology

Node negative H& N cancer (Ca Tonsil) (T3 N0M0)

IMRT treatment plannedPTV66Gy: 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)

Standard IMRT plan: Dosimetry

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

Node negative H& N cancer (Ca Tonsil) (T3 N0M0)

IMRT: 66Gy/30#

Higher scores indicate poorer QOL Score

Dryness of mouth related QOL

Jabbari et al IJROBP 2005

Decrease in salivary flow at follow upGrade II/IV xerostomia at follow up

Kam et al, JCO 2007

Xerostomia evaluation

Subjective assessment Objective assessment

Unsimulated salivary flow after IMRT Simulated salivary flow after IMRT

Li et al, IJROBP 2007

Dose vs salivary function with time

More deterioration of salivary function with higher dose

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

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)

Plan: IMRT boost (24Gy/6#)

(n=1)

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

Dosimetry: IMRT boost (24Gy/6#)

Plan: HDR brachytherapy (24Gy/6#)

Dosimetry: HDR brachytherapy

Dose (Gy)

Max Min Mean

Spinal cord 1.2 - -

Ipsilateral parotid - - 3.1

Contralateral parotid - - 1.4

Plan: CK boost (24Gy/6#)

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

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

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

(n=1)

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

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

Dosimetric comparison between different modality

(n=85)

Teguh et al. IJROBP 2008

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%

Poor swallowing function score after boost treatment with

different modality

Preserved swallowing function with brachytherapy & CK boost

CK is an non-invasive option for boost treatment

Dysphagia related QOL

Teguh et al. IJROBP 2008

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

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

• 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.

Conclusions