Caren van Roekel

61 Radioembolization method often leads to over- or underdosing. Furthermore, the BSA method does not differentiate between tumorous and non-tumorous tissue, leading to undetermined absorbed doses in these tissues. In the SIRFLOX-, FOXFIRE- and FOXFIRE-Global studies, the tumor-absorbed dose was not optimized, leading to an uncertainty about the true effect of radioembolization in the first-line setting (128). 8.2. Neuro-endocrine neoplasms Neuro-endocrine neoplasms (NENs) metastasize to the liver in 50-95% of patients (83). Neuro-endocrine neoplasm metastases generally have a high arterial uptake and are therefore excellent candidates for radioembolization (99). To date, several studies about radioembolization for NEN metastases were published. A meta-analysis of 12 studies showed that median OS ranged from 14-70 months, with a median of 28.5 months. The pooled disease control rate was 86%. The wide range in OS may be due to the inclusion of pancreatic NENs in the analysis, because pancreatic NENs generally have a lower survival than NENs from other primary sites (129)Jia et al. have analyzed the outcome of radioembolization in 36 patients with hepatic metastases of NENs. At 3 months follow-up, overall disease control rate (CR, PR or SD) was 88.9%. There were 16 patients with carcinoid syndrome (flushing, diarrhea) and 15 of them experienced symptomatic improvement after treatment. Side effects were mild, with the exception of 2 patients who developed duodenal ulcers. Median OS was 41 months (130). In a retrospective study, Chansanti et al. have analyzed the tumor-dose relationship in NENs. They included 15 patients with a total of 55 tumors. Primary tumors were located in the pancreas (n=8), the gastrointestinal tract (n=6) and in the lung (n=1). The majority of tumors were hypervascular (80%). Tumor-absorbed dose was estimated using the partition model, as predicted by uptake of 99m Tc-MAA. Mean tumor-absorbed dose was 231.4 Gy and a cutoff value of ≥191 Gy predicted tumor response with 93% specificity. These results show that tumor-absorbed dose estimation based on 99m Tc-MAA uptake is predictive of tumor response and that the partition model can be used for optimal treatment planning (131). Prognostic factors that may influence OS after radioembolization are ECOG score ≥1, higher tumor grade and tumor burden >50% (132). 2