Exploring the Mechanisms and Dynamics of Clonal Evolution Leading to Recurrence in Prostate Cancer

Overview

Prostate cancer is the most common cancer in males in the UK, and current estimates are that 1 in 8 will be diagnosed with prostate cancer in their lifetime. Although surgery or radiotherapy with hormone therapy offers a good chance of cure in localised disease, recurrence can occur, which may cause significant distress, and may shorten the patient's life. In patients with locally advanced disease (disease that has broken through the surrounding capsule of the prostate gland), around 30-40% of patients experience a recurrence. Cancer develops as a result of normal cells acquiring genetic mutations, and localised prostate cancer at diagnosis is commonly made up of different subclones - distinct regions within the patient's cancer with different sets of genetic mutations, each of which may behave differently and be more or less sensitive to treatments. The IMRT clinical trial (CCR 1766) recruited 486 patients who received hormone therapy and radiotherapy to the prostate and lymph nodes in patients with locally advanced prostate cancer. The FORECAST study (FORecasting the Evolution of CAncer of the proState within a Trial) is undertaking genetic sequencing of several regions of these patients' prostate cancers in order to determine which subclones are present at diagnosis, and how they evolved. FORECAST also has permission to obtain and perform sequencing on primary samples from two other large trials in localized prostate cancer. This study seeks to collect blood samples from patients who have experienced a recurrence in whom the primary biopsies have been sequenced as part of FORECAST. Additionally, blood will be collected from any patient in follow up at The Royal Marsden who received radiotherapy and hormone therapy for a localised prostate cancer and has experienced a recurrence but not yet started treatment. In these patients, the FORECAST protocol will be used to undertake genetic sequencing of their original prostate cancer biopsies. Genetic mutations from the cancer can be detected in the blood in patients who relapse, so-called 'liquid biopsies'. By comparing the genetic information between the primary and relapsed cancer, we can detect which subclones present at diagnosis are ultimately responsible for the cancer relapsing, and help us to understand the evolution of prostate cancers over time. This will assist us in predicting at the point of diagnosis which patients are more likely to relapse, so that we may consider escalating primary treatments or treating patients with high-risk subclonal mutations with targeted therapies upfront. As a result, we aim to reduce the number of patients treated for localised prostate cancer experiencing a recurrence. Additionally, although liquid biopsies are well-characterized in metastatic prostate cancer, little is known about their value in patients who have a biochemical-only relapse (patients who have a rising PSA with no evidence of cancer on scans) and this will also be explored.