Tuleasca, ConstantinCarey, GuillaumeBarriol, RomainTouzet, GustavoDubus, FrancoisLuc, DefebvreCarriere, NicolasReyns, Nicolas2024-02-232024-02-232024-02-232024-01-3110.1007/s10143-024-02296-1https://infoscience.epfl.ch/handle/20.500.14299/205446WOS:001154431300001Stereotactic radiosurgery (SRS) is one of the surgical alternatives for drug-resistant essential tremor (ET). Here, we aimed at evaluating whether biologically effective dose (BEDGy2.47) is relevant for tremor improvement after stereotactic radiosurgical thalamotomy in a population of patients treated with one (unplugged) isocenter and a uniform dose of 130 Gy. This is a retrospective longitudinal single center study. Seventy-eight consecutive patients were clinically analyzed. Mean age was 69.1 years (median 71, range 36-88). Mean follow-up period was 14 months (median 12, 3-36). Tremor improvement was assessed at 12 months after SRS using the ET rating assessment scale (TETRAS, continuous outcome) and binary (binary outcome). BED was defined for an alpha/beta of 2.47, based upon previous studies considering such a value for the normal brain. Mean BED was 4573.1 Gy(2.47) (median 4612, 4022.1-4944.7). Mean beam-on time was 64.7 min (median 61.4; 46.8-98.5). There was a statically significant correlation between delta (follow-up minus baseline) in TETRAS (total) with BED (p = 0.04; beta coefficient - 0.029) and beam-on time (p = 0.03; beta coefficient 0.57) but also between TETRAS (ADL) with BED (p = 0.02; beta coefficient 0.038) and beam-on time (p = 0.01; beta coefficient 0.71). Fractional polynomial multivariate regression suggested that a BED > 4600 Gy(2.47) and a beam-on time > 70 min did not further increase clinical efficacy (binary outcome). Adverse radiation events (ARE) were defined as larger MR signature on 1-year follow-up MRI and were present in 7 out of 78 (8.9%) cases, receiving a mean BED of 4650 Gy(2.47 )(median 4650, range 4466-4894). They were clinically relevant with transient hemiparesis in 5 (6.4%) patients, all with BED values higher than 4500 Gy(2.47). Tremor improvement was correlated with BED Gy(2.47 )after SRS for drug-resistant ET. An optimal BED value for tremor improvement was 4300-4500 Gy(2.47). ARE appeared for a BED of more than 4500 Gy2.47. Such finding should be validated in larger cohorts.Life Sciences & BiomedicineBiologically Effective DoseEssential TremorRadiosurgeryTetrastext::journal::journal article::research article