The phytological future of prostate cancer staging: PSMA-PET and the dandelion theory

Abstract

Keywords• metastasis • PET • prostate cancer • PSMA • staging Anybody who has spent more than a few hours cutting or rolling a newly laid lawn will be familiar with the blight of dandelions. Catch one before it is seeded and your lawn stands a chance of retaining its pristine lines and surface (Figure 1). But come out one windy evening to find a freshly seeded flower head and all is lost. Even if you pluck it out you can be certain that the tiny seed pods have been carried to all four corners of your lawn and, given a month, will make their presence known. So much for gardening, but cancer surgery is often similar.One of the core principles of radical surgery is accurate staging in the preoperative setting. For most cancers, it is essential to confirm that the tumor is localized -that is, has not yet seeded -such that radical resection can reasonably be expected to achieve a cure [1]. In prostate cancer, various imaging methods have been employed to provide this information, with European Guidelines currently recommending MRI for local staging and CT/bone scan for exclusion of distant metastases for those with intermediate or high-risk disease [2]. However, it is generally accepted that CT/bone scan has low sensitivity and specificity for detection of metastatic disease, with small foci often missed, or conversely nonspecific lesions being detected such as degenerative bone disease or reactive inflammatory changes in the lymph nodes. This being the case, many men with 'localized disease' deemed to be candidates for radical surgery over the past few decades are likely, in fact, to have had small volume or micrometastatic disease. Although it is hard to tease out which subset of men undergoing surgery are in this group, they form part of a cohort in whom we have seen excellent oncological PSMA-PET is changing how we stage prostate cancer, both in the primary setting and with relapse after treatment. It allows us to identify lesions in the bones and lymph nodes that were not previously visible on conventional imaging with bone scan and CT/MRI. In this Special Report we review the 'state of the art' for PSMA imaging and discuss the implications for treatment decisions in prostate cancer. We liken early high risk or metastatic prostate to a common phytological problem: the dandelion. In this analogous situation, we consider the additional evidence needed for us to start plucking out the original dandelion and for us to focus attention on killing the seeded weeds that are identifiable elsewhere in the lawn.

Harnessing the potential of multimodal radiotherapy in prostate cancer

“…Genomic data suggest that the biology of intermediate metastaNc progression differs from widespread metastasis (22,23), and metastaNc prostate cancer cells might re-seed to the primary lesion (24). Improvements in PET-CT imaging have facilitated precise quanNficaNon of metastases (25,26) and, therefore, increased diagnosis of oligometastaNc prostate cancer (27). PaNents with metastases were historically offered ADT and chemotherapy (9); however, research is now focussing on improving clinical outcomes (28)(29)(30) with a newly established role for radiotherapy within a mulNmodality treatment approach (20,21,31).…”

Protocol for 18F-PSMA PET imaging in staging and management of prostate cancer – a retrospective cohort study

“…However, MRI and CT have low sensitivity 2,3 , and MRI has low specificity for detecting lymph node metastasis [4][5][6] . This is problematic as patients considered appropriate for radical therapy for localised disease may have micro-metastases 7 .…”