Clinical Results of Spot-Scanning based Proton Radiotherapy: Experience at the Paul Scherrer Institute since 1996
Reviewer: Curtiland Deville, MD
The Abramson Cancer Center of the University of Pennsylvania
Last Modified: May 28, 2010
Presenter: E.B. Hug Presenter Affiliation: Paul Scherrer Institute, Center for Proton Therapy, Villagen, Swiss Confederation
Spot scanning based proton therapy was pioneered at the Paul Scherrer Institute (PSI) and has been in routine clinical use there since 1996.
PSI remains the only facility with long-term experience in spot scanning.
While over 6000 patients have been treated predominantly in the eye program, over 500 patients have been treated in the non-eye program.
This analysis reviews the clinical experience, safety, and efficacy of the non-eye program.
537 patients, ages 1-88, were treated from April 1996 – December 2009.
The volume of patients treated has significantly increased since the transition to year-round treatment facility in 2007.
116 of these patients were treated in 2009.
The most frequent tumors treated were:
Chordomas and Chondrosarcomas (51%)
Soft tissue and osteogenic sarcomas (15%)
Meningiomas and primary CNS tumors (18%)
The most common anatomic sites: were: base of skull, CNS, paraspinal, and pelvis.
Between 1996-2005, patients were treated in 2.0 Gy(RBE) fractions four times a week.
Since 2007, patients have been treated with 1.8-2.0 Gy(RBE) fractions five times a week.
Several analyses have been published across tumor sites and select data are presented:
5yr actuarial local contral data are available on 118 patients for:
base of skull chordomas (42 patients) with mean target dose of 74 Gy(RBE) was 81%
base of skull chondrosarcomas (22 patients) with mean target dose of 68 Gy(RBE) was 94%.
spinal chordomas (40 patients) was 66%, and 100% in 19 patients without major surgical stabilization; local control was significantly increased in the non-surgically stabilized vs. surgically stabilized patients (p = 0.003)
3-yr local control for meningioma was 92%
4-yr local control for soft tissue sarcoma was 74%
280 patients have greater than 2 years of follow-up
high grade toxicity was 6% in the skull base and 5% in the paraspinal location.
51 pediatric patients were treated between 2004-2007, including primarily CNS and STS.
Local control is 86% with a median follow-up of 29 months.
All pediatric patients are enrolled in late effects/QOL of study.
The safety and efficacy of spot scanning proton therapy at PSI has been demonstrated across various anatomic sites and tumor types.
The future challenge of spot scanning proton therapy will be the expansion to other tumor types including left-sided breast cancer, and tumors with motion such as lung cancer.
The single institution experience of spot scanning proton therapy at PSI across various, but limited, tumor sites is encouraging.
The reduction in local control observed among surgically stabilized spinal chordomas requires further investigation and may be due to such factors as inherent tumor biology, nonrandomized patient selection, and/or range uncertainty and unfavorable dose distributions due to hardware artifacts.
Increased incorporation of spot scanning and continued long-term data on local control and treatment morbidity are needed.