Small bowel toxicity after high dose spot scanning-based proton beam therapy for paraspinal/retroperitoneal neoplasms
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eider1 · V. Vitolo2 · F. Albertini1 · T. Koch1 · C. Ares1 · A. Lomax1 · G. Goitein1 · E.B. Hug1, 3 1 Center for Proton Therapy, Paul Scherrer Institute, Villigen PSI 2 Fondazione CNAO, Pavia 3 ProCure Proton Therapy Centers, New York
Small bowel toxicity after high dose spot scanning-based proton beam therapy for paraspinal/ retroperitoneal neoplasms Paraspinal/retroperitoneal mesenchymal tumours require high target doses in close proximity to the small bowel (SB) [24, 28]. Acute and late toxicity following conventional photon irradiation are well documented and often constitute dose-limiting factors [4, 17, 18, 26, 30]. In clinical practice, SB tolerance dose constraints are based on the seminal data analysis and recommendations from Emami et al. [6] published in 1991. These authors estimated a tolerance dose (TD) 5/5 of 50 Gy for one-third of the total SB volume (approximately 1800 cm3) and a TD50/5 of 60 Gy (same volume) for late SB toxicities. For whole-organ irradiation, TD5/5 was estimated at 40 Gy and TD50/5 at 55 Gy. These recommendations remained largely unchallenged and have represented the world-wide established consensus for 20 years. However, radiotherapy (RT) techniques have developed dramatically during the past two decades, resulting in improved target dose conformity and signifi cantly reduced radiation-induced acute and late sequelae [5, 12, 20]. As part of the Quantitative Analyses of Normal Tissue Effects in the Clinic (QUANTEC) study, Kavanagh et al. [11] published a comprehensive review of SB toxicities after RT. These authors recommend limiting the absolute volume of irradiated SB to 45 Gy to 70 Gy (RBE), SB received >50 and >60 Gy (RBE) in only 61 and 54% of patients, respectively. Mean SB volumes (cm3) covered by different dose levels (Gy, RBE) were: V20 (n=24): 45.1, V50 (n=19):
17.7, V60 (n=17): 7.6 and V70 (n=12): 2.4. No acute toxicity ≥ grade 2 or late SB sequelae were observed. Conclusion. Small noncircumferential volumes of SB tolerated doses in excess of 60 Gy (RBE) without any clinically-significant late adverse effects. This small retrospective study has limited statistical power but encourages further efforts with higher patient numbers to define and establish high-dose threshold models for SB toxicity in modern radiation oncology. Keywords Organ at risk · Radiation therapy · Follow-up · Chordoma · Sarcoma
Hochdosis-Spot Scanning basierte Protonen-Strahlentherapie von paraspinalen/retroperitonealen Tumoren und Dünndarm-Toxizität Zusammenfassung Hintergrund. Paraspinale und retroperitoneale mesenchymale Tumoren benötigen hohe strahlentherapeutische Dosen. Der Dünndarm ist ein dosislimitierendes Risikoorgan. In dieser retrospektiven Studie verglichen wir Dosis-Volumen-Histogramme des Dünndarms mit Nebenwirkungen nach Protonenstrahlentherapie (PT). Material und Methode. Zwischen 1997 und 2008 erhielten 31 Patienten (Durchschnittsalter: 52,1 Jahre) mit paraspinalen/retroperitonealen Chordomen (81%), Sarkomen (16%) und einem Meningeom (3%) eine Spot-Scanning-basierte PT. Die vers
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