PSMA-PET/MR-data for radiation treatment planning

Summary of the Project

In Germany, prostate cancer is the most common malignancy in men with an annual incidence of 64.000 and approx. 13.000 patients dying of metastatic disease. 

In intermediate and non-metastatic high-risk prostate cancer patients, surgery (with adjuvant radiotherapy) or primary external beam radiotherapy (with anti-androgen treatment) is the therapy of choice. In external-beam irradiation, dose escalation of intermediate and high-risk prostate cancer has been shown to improve the outcome in patients with localized prostate cancer. However, the five-year biochemical relapse rate is still high. 

Increasing the dose to the entire prostate is associated with an increase in severe acute and late toxicity. As local recurrences mainly occur in the primary tumor location, increasing the dose to the dominant intraprostatic lesion (DIL) to an ablative dose is expected to further improve local control rates. In this context, the accurate and precise identification and delineation of the DIL is of utmost importance. 

As a unique and novel approach, the accuracy of DIL detection may be furthered combining multimodality magnetic resonance imaging (MRI) with positron emission tomography (PET) imaging using a PET tracer highly specific for prostate cancer, i.e., prostate-specific-membrane-antigen (PSMA). It is expected that combined PSMA-PET and MR imaging may yield complementary information for the characterization of intraprostatic lesions, ultimately more accurately and reliably identifying the DIL. 

Our aim is to personalize radiotherapy of patients with prostate cancer by incorporation of combined PSMA-PET/MR-data into radiation treatment taking into account the accurate and precise localization and characterization of the DIL, as well as due possibly afore unknown (lymph node, bone) metastases.

Scientific Goals

• Optimize different PET/MR scanner protocols for use in prostate cancer patients. 
• Evaluation of geometric accuracy of PSMA-PET/MR-data in dependence of the diagnostic MR-sequences and PET-isotopes applied on the basis of a novel, for this specific study developed, modified anthropomorphic pelvis phantom.
• Comparison of the definition of the dominant intraprostatic lesion by PSMA-PET and/or MRI.
• Dosimetric comparison of the radiation treatment plans calculated with and without incorporation of PSMA-PET/MR-data in terms of dose to the target volume and to the organs at risk, boosting the dominant intraprostatic lesion.
• Assessment of the frequency of detecting afore unknown metastases and of the therapeutic consequences.