Radioiodine (used in thyroid cancer) predates the word theranostic. Diagnostic radioiodine is used prior to therapeutic radioiodine and exploits exquisite specificity of iodine update and organification by thyrocytes. Bone targeted therapies exploit osteoblastic response to osseous metastasis, utilizing radiolabeled calcium or phosphate analogs. These therapies are often paired with planar or PET bone scans.
Based on data from the ALSYMPCA trial,1 radium-223 dichloride was approved for the treatment of bone-metastatic castration-resistant prostate cancer. It was the first (and currently only) FDA approved alpha particle emitter. Prior to radium-223, Samarium-153 EDTMP and Strontium-89 chloride (beta emitters) were FDA approved for palliation of painful bone metastasis in prostate cancer, demonstrating an excellent palliative response, but with more myelosuppression compared to radium-223.
In terms of recent advancements in theranostics, in 2017, 177Lu-Dotatate demonstrated markedly longer progression-free survival and a significantly higher response rate compared to control octreotide among patients with advanced midgut neuroendocrine tumors. Second, meta-lodobenzylguanidine (aka MIBG lobenguane) is a substrate for the norepinephrine transporter, showing high specific activity and was FDA approved for therapy of advanced pheochromocytoma and paraganglioma in July 2018.
Dr. Pryma concluded his presentation with the following summary points:
- There are many theranostic pairs available today
- Companion diagnostics help avoid futile therapy
- There are several effective first-line theranostic therapies
- These agents have acceptable toxicity profiles, which is different from non-radioactive cytotoxic agents
- There are many new agents coming down the pipeline
Presented by: Daniel A. Pryma, MD, Abramson Cancer Center of the University of Pennsylvania, Philadelphia, PA
Written by: Zachary Klaassen, MD, MSc, Assistant Professor of Urology, Georgia Cancer Center, Augusta University/Medical College of Georgia, Augusta, Georgia, USA, Twitter: @zklaassen_md at the ASCO20 Virtual Education Program, #ASCO20, August 8-10, 2020