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Various single or multi-modality therapeutic options are available to treat pain of bone metastasis in patients with prostate cancer. Different radionuclides that emit β-rays such as (153)Samarium and (89)Strontium and achieve palliation are commercially available. In contrast to β-emitters, (223)Radium as a α-emitter has a short path-length. The advantage of the α-emitter is thus a highly localized biological effect that is caused by radiation induced DNA double-strand breaks and subsequent cell killing and/or limited effectiveness of cellular repair mechanisms. Due to the limited range of the α-particles the bone surface to red bone marrow dose ratio is also lower for (223)Radium which is expressed in a lower myelotoxicity. The α emitter (223)Radium dichloride is the first radiopharmaceutical that significantly prolongs life in castrate resistant prostate cancer patients with wide-spread bone metastatic disease. In a phase III, randomized, double-blind, placebo-controlled study 921 patients with castration-resistant prostate cancer and bone metastases were randomly assigned. The analysis confirmed the (223)Radium survival benefit compared to the placebo (median, 14.9 mo vs 11.3 mo; P < 0.001). In addition, the treatment results in pain palliation and thus, improved quality of life and a delay of skeletal related events. At the same time the toxicity profile of (223)Radium was favourable. Since May 2013, (223)Radium dichloride (Xofigo(®)) is approved by the US Food and Drug Administration.

Somatostatin receptor (sstr) positive tumours vary widely in uptake of radiolabelled somatostatin (sst) analogues. This study determinates variability in lesion uptake of the glycosylated sst analogon Nα-(1-deoxy- d-fructosyl)-Nɛ-(2-[18F]fluoropropionyl)-Lys0-Tyr3-octreotate (Gluc-Lys([18F]FP)-TOCA) and correlates it with lesion size and arterial perfusion as measured on computed tomography (CT). Ten patients with metastasized neuroendocrine carcinomas were investigated with positron emission tomography PET/CT (Biograph 16, Siemens, Germany). Lesion standardized uptake values (SUVs) were determined at ∼50 min post tracer injection according to a 60% isocontour volume of interest around each lesion. Lesion size and enhancement in the arterial phase (hounsfield units, HUs) were derived from CT. 114 lesions in the upper abdomen had a correlate on both, PET and CT. Variability in lesion SUVs was high (SUVmean 22 ± 13). Intraindividually, there was a sigmoid positive correlation between lesion SUV and lesion diameter indicating partial volume effects. Residual variability in lesions ≥3 cm (≥2.5 cm) ranged down to about half (third) of the maximum lesion uptake and remained unexplained by partial volume effects. No correlation with measured HU in the arterial phase was found, neither intraindividually nor interindividually. Partial volume effects were a major source of intraindividual variability in tumour tracer uptake. Lesions below 2.5 to 3 cm should thus be used with caution when performing dose calculations. In larger lesions residual variability in uptake must be considered; it may be due to variable sstr2 expression on the tumours’ cell surfaces. [ABSTRACT FROM AUTHOR]

Positron emission tomography (PET) using 18F-labelled 3′-deoxy-3′-fluorothymidine (FLT) was assessed for therapy monitoring in patients with rectal cancer undergoing neoadjuvant chemoradiotherapy. Ten patients with locally advanced rectal cancer were included and underwent long-course preoperative chemoradiotherapy (total dose 45 Gy, 1.8 Gy/day, concomitant 250 mg/m2 5-fluorouracil) followed by surgery. FLT-PET was performed prior to chemoradiotherapy, 2 weeks after initiation of chemoradiotherapy and preoperatively (3–4 weeks post chemoradiotherapy). FLT uptake was correlated with histopathological tumour regression and changes in T stage. Mean tumour FLT uptake was 4.2±1.0 SUV before therapy and decreased significantly to 2.9 ± 0.6 SUV 14 days after initiation of chemoradiotherapy (−28.6% ± 10.7%, p = 0.005). The preoperative scan showed a further decrease to 1.9 ± 0.4 SUV (−54.7% ± 7.6%, p = 0.005). However, the degree of change in FLT uptake 2 weeks after initiation and after completion of neoadjuvant therapy did not correlate with histopathological tumour regression. FLT-PET did not seem to be a promising method for assessment of tumour response in the studied chemoradiotherapy regimen in patients with rectal cancer. [ABSTRACT FROM AUTHOR]

In this study we evaluated whether positron emission tomography (PET) using the amino acid [[sup 11]C]methyl-L-methionine (MET) may be used for therapy monitoring in patients with rectal cancer who are undergoing preoperative chemoradiotherapy. A total of 41 MET-PET scans were performed in 26 patients with locally advanced rectal cancers. All patients were examined prior to chemoradiotherapy. In 15 patients, METPET was repeated after preoperative chemoradiotherapy (45 Gy radiation dose, 250 mg 5-fluorouracil as continuous infusion). MET uptake prior to and after the completion of chemoradiotherapy was correlated with changes in T stage and histopathological regression. All tumours were visualised with high contrast and had a significantly higher SUV (5.7±2.2) than normal rectum (2.7±0.9) and all other organs in the field of view except the small intestine (3.9±1.7). In all tumours studied prior to and after chemoradiotherapy, MET uptake decreased during therapy (SUV before therapy, 6.2±2.3; SUV after therapy, 2.6±1.2; P=0.0007). However, the degree of change in MET uptake was not correlated with histopathological tumour response. In conclusion, primary rectal cancer can be imaged with MET-PET. However, for the studied chemoradiotherapy regimen, MET-PET did not allow an assessment of the response to therapy. [ABSTRACT FROM AUTHOR]