Inter-fraction motion robustness in a prospective phase II trial on dose-escalated proton reirradiation for locally recurrent rectal cancer.
Phys Imaging Radiat Oncol
; 31: 100634, 2024 Jul.
Article
en En
| MEDLINE
| ID: mdl-39286771
ABSTRACT
Background and purpose:
Intensity modulated proton therapy (IMPT) enables generation of conformal dose plans with organ at risk (OAR) sparing potential. However, pelvic IMPT robustness is challenged by inter-fraction motion caused by constant anatomical variations. In this study, the dosimetric impact of inter-fraction motion on target coverage and dose to OAR was quantified in the prospective phase II study ReRad-II on dose-escalated proton reirradiation for locally recurrent rectal cancer (LRRC). Materials andmethods:
The inter-fraction motion robustness was assessed for the initial twelve patients enrolled in the ReRad-II study. Patients with resectable LRRC were assessed for neoadjuvant IMPT (55 Gy(RBE)/44Fx) and unresectable recurrences for definitive IMPT (57.5-65 Gy(RBE)/ 46-52Fx). Target coverage and dose to OAR were assessed for robustly optimised three-field IMPT, on 12 plan computerized tomography (CT) scans (pCT) - and 47 repetitive control CT scans (cCTs) during the treatment. The target coverage and doses to OAR were re-calculated on each cCT and the mean dose ratio (pCT/cCT-ratio) and target coverage (V95%) was evaluated.Results:
The target coverage was robust with a mean dose pCT/cCT-ratio of 1.00 (+/-1%). The V95% target coverage for every cCT were above the accepted worst-case scenario in the robust evaluation. Considerable variation in bladder-, bowel bag-, and bowel loop volume was observed. The OAR with the largest variation in ratio was the bladder (pCT/cCT-ratio 1.3 (range 0.5-4.7).Conclusions:
IMPT for dose-escalated reirradiation of LRRC provided anatomically robust target coverage despite OAR changes. Inter-fraction motion resulted in OAR doses varying within clinically acceptable range.
Texto completo:
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Colección:
01-internacional
Base de datos:
MEDLINE
Idioma:
En
Revista:
Phys Imaging Radiat Oncol
Año:
2024
Tipo del documento:
Article
País de afiliación:
Dinamarca