New approach for calculating radiation dosimetry allows for individualized therapy



New approach for calculating radiation dosimetry allows for individualized therapy
Figure 1. (A) Initial coarse alignment of full picture quantity for serial 4-, 24-, and 96-h quantitative SPECT photographs. (B) Output of targeted picture registration based mostly on contour-defined masks (dashed area of serial maximum-intensity projections in A). Three-color maximum-intensity projection is used to confirm alignment for serial quantitative SPECT photographs, with third-dimensional contour area highlighted. Black signifies good alignment whereas color-fringing reveals areas with spatial offset. (C) Three-phase exponential curve is generated and parameters are used for subsequent inhabitants evaluation. Credit: SNMMI

Researchers have developed a simplified course of that might improve personalization of most cancers therapy based mostly on a single nuclear medication scan. The novel methodology makes use of a follow-up single photon emission computed tomography/computed tomography (SPECT/CT) scan to acquire dependable radiation dose estimates to tumors and at-risk organs. The examine is revealed in The Journal of Nuclear Medicine.

“In most radionuclide therapies, a fixed amount of radionuclide is administered, which does not take into account individual patient variability in tumor and normal tissue uptake, and hence absorbed dose,” stated John Violet, BSc, MBBS, MRCP, FRCR, Ph.D., FRANZCR, radiation oncologist on the Peter MacCallum Cancer Centre in Melbourne, Australia. “‘Dosimetry-led’ administration, on the other hand, where administered activity is adjusted based upon predictable tumor and normal tissue absorbed doses, has the potential to greatly improve therapeutic outcomes. As dosimetry requires multiple SPECT/CT scans post-therapy, however, it is rarely performed outside clinical trials.”

Rather than depend on a number of SPECT/CT scans to calculate dosimetry, researchers sought to develop a dose-response estimation from a single post-treatment scan. The examine introduced a simplified dosimetry methodology and utilized it to the evaluation of 177Lu-PSMA-617 therapy for metastatic prostate most cancers. 177Lu-PSMA-617 therapy is thought to be a extremely energetic therapy for PSMA-expressing metastatic prostate cancers, however at the moment there isn’t any standardization of how remedy is given.

In the examine, 29 sufferers receiving 177Lu-PSMA-617 have been imaged with SPECT/CT at 4, 24 and 96 hours to characterize tracer pharmacokinetics in tumors and in regular tissues of curiosity. To consider serial measurements, three-dimensional volumes of curiosity have been outlined on the primary picture quantity and a way was developed to mechanically align every contoured subregion and assess pharmacokinetics. This information was used to develop a inhabitants PSMA clearance mannequin for tumor and wholesome organs.

By making use of a generic pharmacokinetic mannequin for PSMA retention, it’s attainable to estimate radiation absorbed dose with a single picture measurement. The vary of added uncertainty will be appreciated based mostly on the variability in inhabitants curves when normalized to the only time level. Tumor dose estimates have been most correct utilizing delayed scanning at instances past 72 hours. Dose to wholesome tissues was finest characterised by scanning sufferers within the first two days of remedy due to the bigger diploma of tracer clearance on this early section.

“This work shows for the first time that following Lu-PSMA administration, it is possible to determine a good estimate of activity and absorbed dose with just a single measurement,” famous Violet. “Simplification of dosimetry methods to make them a routine application would greatly assist in developing radiobiological models specific to Lu-PSMA, and other radionuclide therapies, allowing optimization of therapy for individual patients that are maximally effective and safe.”

Improved understanding of radiation dose-response to radionuclide could present a rationale for shifting away from fastened exercise prescriptions. This would enable clinicians to tailor therapies based mostly on a person affected person’s physiology so successive remedy cycles might be adjusted to yield improved remedy outcomes. “The routine application of radiation dosimetry would be an important step in achieving the goal of ‘dosimetry-led’ treatment, providing significant improvements in both the safety and efficacy of treatment,” defined Violet. “The adoption of routine dosimetry across molecular imaging and nuclear medicine in general would be a major advance in the field for both the clinical application of established therapies and the optimization of novel treatments.”

Targeted radionuclide therapy enhances prostate cancer response to immunotherapies

More data:
Price A. Jackson et al, Radiation Dosimetry in 177Lu-PSMA-617 Therapy Using a Single Posttreatment SPECT/CT Scan: A Novel Methodology to Generate Time- and Tissue-Specific Dose Factors, Journal of Nuclear Medicine (2019). DOI: 10.2967/jnumed.119.233411

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Society of Nuclear Medicine and Molecular Imaging

New approach for calculating radiation dosimetry allows for individualized therapy (2020, August 11)
retrieved 11 August 2020

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