Can peptide receptor radionuclide therapy be safely applied in florid bone metastases? A pilot analysis of late stage osseous involvement.

AIM: Highly advanced metastatic bone disease with extensive osseous infiltration of neuroendocrine tumours (NET) may preclude patients from treatment with peptide receptor radionuclide therapy (PRRT) in concern about haematotoxicity. This study aims to assess the safety and efficacy of PRRT with 177Lu-octreotate in a patient cohort with this condition. PATIENTS, METHODS: 41 PRRT courses were performed in 11 patients with gastroenteropancreatic neuroendocrine tumours (GEP-NET) and florid bone metastases (severely advanced widespread metastatic bone disease). A mean activity of 6.95 GBq 177Lu-octreotate was administered per treatment cycle, aimed at four courses with standard intervals of 3 months. Haematological parameters were determined prior to each treatment course, in 2-4 weeks intervals between the courses, 8-12 weeks after the last course of PRRT and in 3 monthly intervals thereafter. Toxicity was recorded using Common Terminology Criteria for Adverse Events v3.0. Restaging was performed 3 months after termination of PRRT with CT/MRI and functional imaging (modified MDA criteria). RESULTS: Significant (grade III-IV), reversible haematotoxicity occurred in 4 (35%) patients and after 10 (24%) administrations. It either resolved spontaneously (1 patient) or was controlled by supportive measures (3 patients), such as blood transfusions (3 patients) or deferral of the subsequent therapy cycle (1 patient). Patients returned to baseline blood values within up to 23 months after termination of PRRT. The observed treatment response of bone metastases consisted of a partial response in 2, a minor response in 1, stable disease in 7, and progressive disease in 1 patient. Of the 4 patients with metastatic bone pain, 1 experienced complete and 3 partial resolution of symptoms within 3-10 weeks after commencement of PRRT. CONCLUSION: These preliminary data indicate that PRRT with 177Lu-octreotate can be safely applied even in florid bone metastases with extensive, severely advanced osseous replacement. The higher myelosuppression rate was not associated with serious complications and should not preclude patients from being treated and potentially experiencing remarkable treatment efficacy despite the very advanced stage.

Liver and lymph node metastases of prostate cancer visualized on post-therapy imaging after treatment with 188Re-HEDP / Metástasis hepáticas y linfáticas del cáncer de próstata en la imagen post-terapia con 188Re-HEDP

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Residual activity after radioembolization of liver tumours with 90Y resin microspheres. A safe calculation method.

UNLABELLED: The actual number of resin microspheres is approximately 30-60 times higher than glass microspheres per 3 GBq vial. Thus, radioembolization (RE) with resin microspheres exerts an embolization effect besides the radiation effect. This embolization effect can occasionally cause early back flow of the microspheres before application of the entire calculated dose. To avoid these adverse side effects, RE has to be terminated at an earlier time point. Measurement of the residual activity in the delivery box, which includes the v-vial, tube and catheter, to calculate the achieved target dose is often challenging. The aim of the current study was to establish a post-RE measurement method comparable to the glass microspheres method without unnecessary radiation exposure to the staff and risk of contamination. METHODS: Two different measurements were performed. First, total radioactivity in the shipping vial was measured in an ion chamber and then it was put in the delivery box and the radiation was measured from a 30 cm distance from the centre of the box with a dosimeter. The required radioactivity was then transferred to the v-vial, and the shipping vial was measured again. After that, the v-vial was measured from the same distance from the centre of the box with dosimeter. RESULTS: Altogether 62 times the shipping vial with different activities were measured with a significant positive correlation between the amount of the activity measured in the iron chamber and the radiation dose, measured with dosimeter (r² = 0.98; p< 0.001). There was also a strong positive correlation between these measurements of the v-vial (r² = 0.98; p< 0.001). CONCLUSION: With measurement of the residual activity in the delivery box using a dosimeter the percentage of the whole injected activity can be easily calculated. This facilitates the calculation of the actual, achieved target and non-target dose in those cases, where therapy had to be stopped because of eminent flow reversal or obstruction.