IMRT - A New Treatment Method for Nasopharyngeal

Cancer

Wen-Shan Liu1, Hsiang-Chi Kuo1, Bin S. Teh2, E. Brian Butler2

1Chung Shan Medical & Dental College Hospital2Department of Radiation Oncology, Baylor Colle

ge of Medicine

INTRODUCTION

Is conventional radiotherapy good enough for NPC?

Local control

• T1 - T2: 80 - 90 %

• T3 - T4: 20 - 60 %

Grade III - IV Complications

• Temporal lobe necrosis: 2 - 33.3 %

• Hearing impairment: 3 - 30.9 %

• Cranial neuropathy: 0 - 4.2 %

Normal tissue complications

• Otitis media: 5 - 41.8 %

• Trismus: 3 - 12 %

• Xerostomia: 35 - 100 %

• Neck fibrosis: 3 - 36.4 %

• Osteonecrosis: 0 - 2 %

Three Major Issues of the NPC

• How to improve the local control especially for T3 and T4 patients

• How to reduce the post-irradiation late sequelae

• How to reduce the ratio of distant metastasis

The potential benefit of IMRT for NPC

• Improve the local control especially for concave shape tumors

• Reduce the post-irradiation complications

• Reduce the rate of distant metastasis by improving the local control

Contents• To present the preliminary results of

IMRT for nasopharyngeal cancer

• To present the CT-based target defining for nasopharyngeal cancer

• To demonstrate the fractionation strategies for intensity-modulated radiation therapy of nasopharyngeal cancer

Patients and Methods

• Sept to Dec 2000: 13 patients

• Staging: T1-2, N0-2, M0 (AJCC 1997)

• Age: from 24 to 72 years old

• Male : female = 10 : 3

Patient’s characteristicsPatient Sex Age Histology Stage Remark1 F 52 Type III T1N0M02 F 72 Type II T2N2M03 M 42 Type III T1N1M04 M 48 Type II T1N0M05 M 24 Type III T1N1M06 M 72 Type III T2N0M07 M 53 Type III T2N1M08 M 47 Type II T2N0M09 F 58 Type III T2N1M010 M 53 Type III T2N2M0 7.2 Gy11 M 65 Type II T1N0M0 10.0 Gy12 M 37 Type II T2N2M0 9.0 Gy13 M 34 Unknown Recurrence

The procedures of IMRT for nasopharyngeal cancer

• Immobilization

• Imaging acquisition and contouring

• Dose calculation with inverse planning

• Quality assurance

• Verification the position

• Portal imaging with EPID

• IMRT

Immobilization

Imaging acquisition and contouring

Dose calculation with inverse planning

• Varians Helios planning system

Dose limits of inverse planning

Dose limits to various normal structuresNormal structures Dose limits (Gy)Brainstem 50Spinal cord 40Lens 12Optic nerves/chiasm 45Parotid gland (Ipsilateral) 35Parotid gland (Contralateral) 25Mandible 58

Inverse planning

Dose to various target volumesTarget volume Dose (Gy) Fraction

numberGTV 68 – 71 32-33CTV 60 32 - 33

IMRT QA and Treatment

MLC Controller

TPS Leaf Motion

Treatment Machine

Record andVerify

Log File

Indep. MU Calc.

DMLC Port Film/DRR Comparison

Film/Ion Chamber Verification

??

NPC2:測量值 NPC2:運算值

NPC4:測量值 NPC4:運算值

Verification the treatment position by simulation

Verification the treatment position by portal imaging (EPID)

Intensity-modulated radiotherapy (IMRT)

RESULTS

Acute Reaction

Acute reactions of the completed five patientsStructures G I (%.) G II G IIISkin 3 (60) 2 (40) 0Mucosa 0 0 5 (100)Salivary gland 0 2 (40) 3 (60)Pharynx 0 3 (20) 2 (80)

Dosimetry

Dosimetry of various targetsTargets Prescribed

dose

D95 Min Max Mean Median Volume

(cc)

GTV 68-71 Gy 69.6 60.8 73.0 70.3 70.5 44.3

CTV 56-60 Gy 61.6 38.8 74.9 65.7 65.8 398.7

Dosimetry of various normal structuresTargets Limits D50 Min Max Mean Median Volume

(cc)Brain

stem

45.0 34.3 22.8 53.1 34.4 34.4 21.0

Spinal

cord

40.0 38.8 25.4 46.3 34.1 39.0 13.5

Optic

nerve

45.0 29.6 20.1 47.7 23.7 32.0 0.46

Chiasm 45.0 45.8 32.8 56.0 33.9 48.9 1.0

Eye ball 12/45 10.4 1.51 20.4 9.3 11.0 11.4

Parotid 35.0 32.8 12.1 68.6 37.4 33.2 19.4

Head 24.7 0.05 78.4 28.4 25.5 4104.9

Response evaluation by CT scan

Response evaluation by CT scan

Discussion

• How to define the treatment targets?

• How to decide the doses to the different targets and different critical organs?

• Is the IMRT really better than conventional radiotherapy?

How to define the treatment targets?

How to define the treatment targets?

• Medial: c-spine body and pharyngeal wall

• Lateral: excluding parotid, sternocleido-mastoid & pterygoid

• Post.: tip of spinous process

How to define the treatment targets?

• Medial: c-spine body and pharyngeal lumen

• Lateral: edge of sternocleidomastoid m. or medial 2/3

• Post.: tip of spinous process

How to decide the doses to the different targets and different

critical organs?

• SMART: simultaneous modulated accelerated radiation therapy, Dr. Butler and Dr. Teh, 1999

• SIB: simultaneous integrated boost, Dr. Mohan and Dr. Wu, 2000

SMART IMRT Schedule

• Primary target: 2.4 Gy per fraction

• Secondary target: 2.0 Gy

Butler EB, Teh BS, Grant WH et al: SMART (simultaneous modulated accelerated radiation therapy) boost: A new accelerated fractionation schedule for the treatment of head and neck cancer with intensity modulated radiotherapy. Int J Radiat Oncol Biol Phys, v45, no.1, pp21-32, 1999

SIB IMRT Schedule

• Primary target: 2.2 Gy per fraction

• Secondary target: 1.8 Gy

Mohan R, Wu Q, Maning M and Schmidt-Ullrich R: Radiobiological considerations in the design of fractionation strategies for intensity-modulated radiation therapy of head and neck cancers. Int J Radiat Oncol Biol Phys, v46, No.3, pp619-630, 2000

Is the IMRT really better than conventional or 3-D conformal

radiotherapy?

IMRT Two opposed

IMRT Two opposed

IMRT Two opposed

DVH of 3-D conformal radiotherapy

DVH of intensity-modulated radiotherapy

Lower skin reaction with IMRT technique

IMRT must be applied very carefully!

Dawson LA, Anzai Y, Marsh L et al: Patterns of local-regional recurrence following parotid-sparing conformal and segmental intensity-modulated radiotherapy for head and neck cancer. Int J Radiat Oncol Biol Phys, V46, No.5, pp1117-1126, 2000