Artikel
Salvage treatment of small sized recurrent metastasis with stereotactic Iodine-125 brachytherapy: a risk-benefit analysis
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Veröffentlicht: | 13. Mai 2014 |
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Gliederung
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Objective: In the current retrospective study, low-activity iodine-125 brachytherapy (SBT) was used either as initial treatment of small sized metastases (de-novo group) or as salvage treatment after previously applied external beam radiation and/or radiosurgery (recurrence group). Risk and benefit of both strategies were compared.
Method: Patients with small sized metastases (diameter less than or equal 4 cm), a controlled extra-cerebral tumor status and a Karnofsky performance score (KPS) of at least 70 were considered eligible. After histological verification of the metastasis by stereotactic biopsy, SBT using low activity iodine-125 seeds were performed. The prognostic influence of patient- tumor- and treatment factors was estimated with the proportional hazards model. The entire dose applied to the early and late responding tissue of each patient was assessed by calculation of the biologically effective tumor dose (BED) according to the formula of Fowler and Dale.
Results: Forty patients (17 males, 23 females; median age 59 ± 9 years) were included. The de-novo (N=20) and the recurrence group (n=20) did not differ in terms of age, KPS, tumor size, tumor location (deep seated vs lobar), tumor histology, number of metastases, extracerebral tumor status, SBT-related tumor dose, and applied treatment strategies after SBT. The median reference dose of SBT was 50 Gy and the median dose rate 15 cGy/h. The median tumor volume was 3.9 cm3 ± 2.7 cm3. In the recurrence group all patients had previously received conventionally fractionated external beam radiation (tumor dose: 40 Gy), and 7 patients had undergone additional radiosurgery (median tumor dose: 19 Gy). The BED for the late responding tissue was significantly higher in the recurrent group than in the de-novo group (180.1 Gy10 vs 103.7 Gy10; p=0.001). After SBT, the one-year local tumor control rate was 92% in the de-novo group and 75% in the recurrence group; the difference was statistically not significant (p=0.95). No permanent side effects were seen after SBT. Transient edema occurred in two patients of the recurrence group. No risk factors for radiogenic complications and no prognostic factors could be identified.
Conclusions: Continuously applied interstitial irradiation with low-dose rates using Iodine-125 SBT is an extremely attractive treatment option for selected patients with recurrent brain metastases.