title: Radioembolisation with 90Y-microspheres: dosimetric and radiobiological investigation for multi-cycle treatment.
abstract: BACKGROUND
  Radioembolisation with (90)Y-microspheres is a new locoregional treatment of hepatic lesions, usually applied as single cycle. Multi-cycle treatments might be considered as a strategy to improve the risk-benefit balance. With the aim to derive suitable information for patient tailored therapy, available patients' dosimetric data were reviewed according to the linear-quadratic model and converted into biological effective dose (BED) values. Single vs. multi-cycle approaches were compared through radiobiological perspective.
  
  
  METHODS
  Twenty patients with metastatic lesions underwent radioembolisation. The (90)Y-administered activity (AA) was established in order to respect a precautionary limit dose (40 Gy) for the non-tumoral liver (NTL). BED was calculated setting alpha/beta = 2.5 Gy (NTL), 10 Gy (tumours); T (1/2,eff) = T (1/2,phys) = 64.2 h; T (1/2,rep) = 2.5 h (NTL), 1.5 h (tumours). The BED to NTL was considered as a constraint for multi-cycle approach. The AA for two cycles and the percent variations of AA, tumour dose, BED were estimated.
  
  
  RESULTS
  In one-cycle, for a prescribed BED to NTL of 64 Gy (NTL dose = 40 Gy), AA was 1.7 (0.9-3.2) GBq, tumour dose was 130 (65-235) Gy, and tumour BED was 170 (75-360) Gy. Considering two cycles, approximately 15% increase was found for AA and dose to NTL, with unvaried BED for NTL. Tumour dose increase was 20 (10-35) Gy; tumour BED increase was 10 (3-11) Gy. In different protocols allowing 80 Gy to NTL, the BED sparing estimated was approximately 50 Gy (two cycles) and 65 Gy (three cycles).
  
  
  CONCLUSIONS
  From a radiobiological perspective, multi-cycle treatments would allow administering higher activities with increased tumour irradiation and preserved radiation effects on NTL. Trials comparing single vs. multiple cycles are suggested.
authors.affiliation: Unit of Medical Physics, European Institute of Oncology, Milan, Italy.
authors.forename: Marta
authors.initials: M
authors.lastname: Cremonesi
authors.forename: Mahila
authors.initials: M
authors.lastname: Ferrari
authors.forename: Mirco
authors.initials: M
authors.lastname: Bartolomei
authors.forename: Franco
authors.initials: F
authors.lastname: Orsi
authors.forename: Guido
authors.initials: G
authors.lastname: Bonomo
authors.forename: Demetrio
authors.initials: D
authors.lastname: Aricò
authors.forename: Andrew
authors.initials: A
authors.lastname: Mallia
authors.forename: Concetta
authors.initials: C
authors.lastname: De Cicco
authors.forename: Guido
authors.initials: G
authors.lastname: Pedroli
authors.forename: Giovanni
authors.initials: G
authors.lastname: Paganelli
mesh_terms: D004621:Embolization, Therapeutic / Q000379:methods*; D005260:Female; D006801:Humans; D008099:Liver / Q000000981:diagnostic imaging / Q000473:pathology / Q000528:radiation effects; D008297:Male; D008863:Microspheres; D008875:Middle Aged; D011829:Radiation Dosage; D015899:Tomography, Emission-Computed, Single-Photon; D015021:Yttrium Radioisotopes / Q000737:chemistry / Q000627:therapeutic use
chemical_list: D015021:Yttrium Radioisotopes