DOI: 10.1007/s00259-016-3609-9Pages: 788-800

The 68Ga/177Lu theragnostic concept in PSMA targeting of castration-resistant prostate cancer: correlation of SUVmax values and absorbed dose estimates

1. Medical University Innsbruck, Department of Nuclear Medicine

2. Medical University of Innsbruck, Department of Radiotherapy / Radiation Oncology

3. Medical University of Innsbruck, Department of Urology

4. Medical University of Innsbruck, Department of Radiology

Correspondence to:
Irene Virgolini
Tel: +43 (0)50 504-22650
Email: irene.virgolini@i-med.ac.at

Close

Abstract

Introduction

A targeted theragnostic approach based on increased expression of prostate-specific membrane antigen (PSMA) on PC cells is an attractive treatment option for patients with metastatic castration-resistant prostate cancer (mCRPC).

Methods

Ten consecutive mCRPC patients were selected for 177Lu-PSMA617 therapy on the basis of PSMA-targeted 68Ga-PSMA-HBED-CC PET/CT diagnosis showing extensive and progressive tumour load. Following dosimetry along with the first therapy cycle restaging (68Ga-PSMA-HBED-CC and 18F-NaF PET/CT) was performed after 2 and 3 therapy cycles (each 6.1 ± 0.3 GBq, range 5.4–6.5 GBq) given intravenously over 30 minutes, 9 ± 1 weeks apart. PET/CT scans were compared to 177Lu-PSMA617 24-hour whole-body scans and contrast-enhanced dual-phase CT. Detailed comparison of SUVmax values and absorbed tumour doses was performed.

Results

177Lu-PSMA617 dosimetry indicated high tumour doses for skeletal (3.4 ± 1.9 Gy/GBq; range 1.1–7.2 Gy/GBq), lymph node (2.6 ± 0.4 Gy/GBq; range 2.3–2.9 Gy/GBq) as well as liver (2.4 ± 0.8 Gy/GBq; range 1.7–3.3 Gy/GBq) metastases whereas the dose for tissues/organs was acceptable in all patients for an intention-to-treat activity of 18 ± 0.3 GBq. Three patients showed partial remission, three mixed response, one stable and three progressive disease. Decreased 177Lu-PSMA617 and 68Ga-PSMA-HBED-CC uptake (mean SUVmax values 20.2 before and 15.0 after 2 cycles and 11.5 after 3 cycles, p < 0.05) was found in 41/54 skeletal lesions, 12/13 lymph node metastases, 3/5 visceral metastases and 4/4 primary PC lesions.

Conclusion

Due to substantial individual variance, dosimetry is mandatory for a patient-specific approach following 177Lu-PSMA617 therapy. Higher activities and/or shorter treatment intervals should be applied in a larger prospective study.

This article is freely available, click here to access the full text/PDF

  • Accepted: Dec 23, 2016
  • Online: Jan 12, 2017

Article Tools

eanm
EJNMMI Ad