News Release 

Therapy for neuroendocrine tumors may be improved by patient-specific dosimetry

Society of Nuclear Medicine and Molecular Imaging

In neuroendocrine tumor treatment, different methods of predicting patient response may be required for different patients, according to new research published in the October issue of The Journal of Nuclear Medicine. By tailoring the method to the specific patient, physicians may better predict the effectiveness of treatment.

"The present study aimed to develop a method for patient-specific determination of activity in bone marrow, enabling a more personalized dosimetry," explains Linn Hagmarker, PhD, a student at the Department of Radiation Physics at the Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, Sweden. "Personalized bone marrow dosimetry can be used as a factor to prevent bone marrow toxicity during treatment and to identify the risk for developing myelodysplastic syndrome and acute leukemia."

The Swedish team developed a hybrid planar and SPECT imaging method to determine the bone marrow absorbed dose. In a cohort study of 46 patients treated with 177Lu-DOTATATE, it was established that this planar image-based method was not influenced by skeletal metastases, whereas hybrid dosimetry methods, based on planar and SPECT images, was influenced by skeletal metastases and by the vertebrae used for SPECT quantification. All methods demonstrated statistically significant dose-response correlations. The planar method had the best correlation for patients without skeletal metastasis, and the hybrid methods had the best correlation for patients overall, including the cohort with skeletal metastasis.

The study results show that different dosimetry methods might be required for optimal prediction of hematologic toxicity in patients with and without skeletal metastases.

"Since the active bone marrow varies within vertebrae, we determined the activity concentration in vertebrae using several methods," said Hagmarker. "We also investigated whether the bone marrow absorbed dose correlated with hematologic response early during treatment. The image-based dosimetry methods demonstrated that increased absorbed bone marrow doses result in higher platelet toxicity, and the platelet response is influenced by infiltrating metastases."

She adds, "The absorbed dose to the spleen also influences the platelet response by acting as a reservoir for platelets. In addition, age, gender, and pre-treatment (which all influence the vertebrae constitutents of adipose and active bone marrow cells) must be incorporated when modeling platelet response and developing predictive models for toxicity."

Looking at further implications of this research, Hagmarker notes, "Current evidence indicates that kidneys can tolerate mean absorbed doses above the general dose-limit. Recent studies have also reported the use of retreatment for patients with progressed disease. If higher renal mean absorbed doses are accepted, higher total activity could be administered, and bone marrow toxicity might become the dose-limiting factor."

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The authors of "Bone Marrow Absorbed Doses and Correlations with Hematologic Response During 177Lu-DOTATATE Treatments Are Influenced by Image-Based Dosimetry Method and Presence of Skeletal Metastases" include Linn Hagmarker, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden; Tobias Rydén, Martijn van Essen, Peter Gjertsson, and Johanna Svensson, Sahlgrenska University Hospital, Gothenburg, Sweden; Anna Sundlöv, Skåne University Hospital and Lund University, Lund, Sweden; Katarina Sjögreen Gleisner, University of Lund; and Peter Bernhardt, Sahlgrenska Academy, University of Gothenburg and Sahlgrenska University Hospital Gothenburg, Sweden.

Please visit the SNMMI Media Center for more information about molecular imaging and precision medicine. To schedule an interview with the researchers, please contact Rebecca Maxey at (703) 652-6772 or rmaxey@snmmi.org. Current and past issues of The Journal of Nuclear Medicine can be found online at http://jnm.snmjournals.org.

About The Journal of Nuclear Medicine

The Journal of Nuclear Medicine (JNM) is the world's leading nuclear medicine, molecular imaging and theranostics journal, accessed more than 9 million times each year by practitioners around the globe, providing them with the information they need to advance this rapidly expanding field.

JNM is published by the Society of Nuclear Medicine and Molecular Imaging (SNMMI), an international scientific and medical organization dedicated to advancing nuclear medicine and molecular imaging--precision medicine that allows diagnosis and treatment to be tailored to individual patients in order to achieve the best possible outcomes. For more information, visit http://www.snmmi.org.

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