Theranostics by Nuclear Medicine Technology is a new hope for Prostate Cancer Patients

King Hussein Cancer Center, Amman, Jordan

History

A 72-year-old male patient with a metastatic castration resistant prostate cancer (mCRPC) to bone. The patient presented with disease progression after hormonal treatment, chemotherapy and radiotherapy. He was referred to the nuclear medicine department at KHCC for potential targeted radionuclide therapy by Lutetium-177 PSMA (PRLT).

Ga68 PSMA PET/CT and F18 FDG-PET/CT were ordered for the patient to confirm his eligibility for this innovative treatment. Patient would be eligible for PRLT if his PET scan demonstrates high and sufficient expression of PSMA exceeding that of FDG expression.

Interpretation of Images

Baseline Ga68 PSMA PET/CT scan showed high expression of PSMA in the widespread skeletal metastases (Fig. 1A) that was significantly exceeding the level of FDG metabolic activity.

In addition, no metastatic deposits were identified as only FDG avid without sufficient PSMA expression throughout the whole-body PET scans. Therefore, patient was regarded as a candidate for PRLT.

Patient received two doses of PRLT (spaced 8 weeks each) and post therapy Lu-177 SPECT/CT scans showed adequate localization of the therapeutic Lu-177 PSMA radiotracer in the targeted metastatic lesions (Fig. 2).

Follow up Ga68 PSMA PET/CT scan was done after the two doses of PRLT and showed dramatic regression (almost resolution) in the PSMA expression of the widespread bone metastases. These findings were associated with significant decline in the PSA value from 179 to 1.8, as well as significant improvement in the patient’s quality of life indicating excellent response to this targeted treatment.

Comments

Progressive metastatic castration-resistant prostate cancer is a highly lethal disorder and new effective therapeutic agents that improve patient outcomes are urgently needed.

Lutetium-177 [1⁷⁷Lu]-PSMA-617, a radiolabeled small molecule, binds with high affinity to prostate- specific membrane antigen (PSMA) enabling beta particle therapy targeted to metastatic castration-resistant prostate cancer.

We aimed to investigate the safety, efficacy, and effect on quality of life of [1⁷⁷Lu]-PSMA-617 in men with metastatic castration-resistant prostate cancer who progressed after standard treatments.

Cancer is expected to be classified by molecular phenotyping in the early future, while the organ site would be a secondary classification. Molecular phenotyping will be determined by molecular pathology and molecular imaging such as PET/CT, SPECT/CT, MRI and Optical imaging using cancer type specific probes.

Molecular imaging is a great asset for personalized medicine by in vivo characterization and early diagnosis, linking a target identification with treatment, risk assessment, therapy selection and monitoring treatment. Theranostics (Molecular endoradiotherapy) based on molecular phenotyping is a new hope in treatment of cancer. Prostate cancer is successful current applications of theranostics. PRLT is highly effective for the treatment of mCRPC, even in advanced cases with favorable overall survival compared to available treatments. Excellent partial response with significant prolonged overall survival and symptoms control are currently achievable as we have seen in the discussed case here.