Learn More At: Northwest Hospital Gamma Knife Center Dr. Sandra Vermeulen, M.D. Swedish Cancer...

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Northwest Hospital

Gamma Knife Center

Dr. Sandra Vermeulen, M.D.

Swedish Cancer Institute

Northwest Hospital Gamma Knife Center

Seattle, Washington


Gamma Knife Centers in the State of Washington

• Seattle, North

• Seattle, Downtown

• Spokane

• “Tacoma”


Northwest Hospital

• Founded in 1960

• Non-profit community hospital

• 281 beds


Northwest Gamma Knife Center

• First Patient treated in the Summer of 1993

• Approx. 2500 total patients treated

• 3 Radiation Oncologist on site

• 9 Neurosurgeons


Tumor Institute Radiation Oncology Group

Members

T. Barnett, J. Blasko, B. Douglas,S. Eulau, P. Grimm, T. Mate, V. Mehta, R. Meier, A. Morris, J. Sylvester, R.Takamyia, A.Tesler, J. Travaglini, S.Vermeulen



• 50% -50% ownership between 2 hospitals

• No physician equity ownership

• 40% of the billing is Global


Gamma Knife IndicationsTumor Types

1/3 Malignant

1/3 Functional

1/3 Benign


Consults and Consents

• All Patients are seen by Neurosurgery and Radiation Oncology before the Gamma Knife Treatment is scheduled

• All other possible treatment options are explored

• If the tumor being treated is malignant, the GK procedure is coordinated with patient’s chemotherapy schedule


Gamma Knife Follow-UpMalignant Tumors

• Patient follow-up is through the department of Radiation Oncology

• Malignant tumors are followed with an MRI scan every 2 months for 1-2 year


Gamma Knife Follow-UpBenign Tumors and

Functional Cases• Patient follow-up is through the

department of Neurosurgery• Benign tumors are scanned with an MRI

on an every 6 month bases for 3-5 years• AVM are followed angiographically

every year until the nidus occludes• Functional cases rarely return for a

second GK procedure


Gamma Knife Referrals

50% of cases are initially seen by Radiation Oncology


Gamma Knife Frame Placement

If multiple metastases are present or the patient has had more than one GK procedure, identifying current targets on the most recent scan will aid in frame placement


Gamma Knife Procedure

• Pre-scheduled MRI times

• Conscious sedation

• Check anticonvulsant levels day before or morning of the procedure

• Steroids


Gamma Knife“Automatic Positioning System”

If there are multiple metastases in vast different locations of the brain, APS will add considerable time to the treatment. As a result, only 1 or 2 cases for that day should be considered.


Northwest Hospital Gamma Knife Center Staffing

• 3 Nurses

• 2 Receptions

• 2 Physicist

• 1 research assistant


Gamma KnifeClinical Research

• What is the % of symptomatic necrosis and how does this correlate with volume size?

• If the tumor is “too” big, can the treatment be staged?

• What is the lowest effective single fraction dose for treating meningiomas?


Prolonged Corticosteroids use in the Treatment of Brain

Metastases with Accelerator Based Radiosurgery compared to Gamma Knife Radiosurgery

S Vermeulen, J Rasis, B Mason



Brain metastases experience previously

published in 1996• 288 tumors in 107 patients

• 91% tumor control

• < 5% required continuous steroid support


pReference Stereotactic Systems

• Product of Northwest Medical Physics

• Treatment delivery• Multiple arcs, multi-static fields with custom

blocks, multi-leaf collimater field arrangements

• Frameless• Documented < sub millimeter accuracy by an

independent report from MD Anderson Cancer Center in 1997


pReference Stereotatic System

Between 11/98 and 1/00, 56 brain metastases in 26 patients were treated at the Swedish Cancer

Institute


RTOG 95-05

• Tumor Size• 2.0 cm (2.4 Gy), 2.1-3.0 cm (18 Gy), 3.1-4.0 cm

(15 Gy)

• Max Dose/Prescription Dose < 2

• PITV(volume of prescription isodose /target volume) required to be between

1-2• ACHIEVED IN 44/50 TARGETS OR 88 %


Target Characteristics

• 50/23 targets/patients were eligible for review

• Tumor Volume mean 3.9 cc (0.3 – 29.8 cc)

• Iso mean 89.4% (82-100%)• 40/50 or 80% treated with a

single fraction


Results

• Mean survival 9 months (range 2-18 m)

• 48/50 or 96% Tumor Control

• 5/50 or 10% complete disappearance of the target on subsequence scans

• 15/23 patients or 65% required continuous steroid support


Conclusion

Possibly less than a 20 % dose gradient within the tumor volume contributes to a limited degree of tumor sterilization and complete response resulting in greater steroid use


Northwest Gamma Knife

Learn More At: Northwest Hospital Gamma Knife Center Dr. Sandra Vermeulen, M.D. Swedish Cancer...

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