Tumour responses to radiotherapy are currently primarily assessed by changes in size. Imaging permits non-invasive, whole-body assessment of tumour burden and guides treatment options for most tumours. However, in most tumours, changes in size are slow to manifest and can sometimes be difficult to interpret or misleading, potentially leading to prolonged durations of ineffective treatment and delays in changing therapy. Functional imaging techniques that monitor biological processes have the potential to detect tumour responses to treatment earlier and refine treatment options based on tumour biology rather than solely on size and staging. By considering the biological effects of radiotherapy, this review focusses on emerging functional imaging techniques with the potential to augment morphological imaging and serve as biomarkers of early response to radiotherapy.

Molecular radiotherapy, or targeted radionuclide therapy, uses systemically administered drugs bearing a suitable radioactive isotope, typically a beta emitter. These are delivered via metabolic or other physiological pathways to cancer cells in greater concentrations than to normal tissues. The absorbed radiation dose in tumour deposits causes chromosomal damage and cell death. A partner radiopharmaceutical, most commonly the same vector labelled with a different radioactive atom, with emissions suitable for gamma camera or positron emission tomography imaging, is used to select patients for treatment and to assess response. The use of these pairs of radio-labelled drugs, one optimised for therapy, the other for diagnostic purposes, is referred to as theragnostics. Theragnostics is increasingly moving away from a fixed number of defined activity administrations, to a much more individualised or personalised approach, with the aim of improving treatment outcomes, and minimising toxicity. There is, however, still significant scope for further progress in that direction. The main tools for personalisation are the following: imaging biomarkers for better patient selection; predictive and post-therapy dosimetry to maximise the radiation dose to the tumour while keeping organs at risk within tolerance limits; imaging for assessment of treatment response; individualised decision making and communication about radiation protection, adjustments for toxicity, inpatient and outpatient care.

Introduction: Perioperative mortality of patients who undergo heart valve surgery for carcinoid heart valve disease has been observed to be high (5%–10%). We investigated whether peptide receptor radiotherapy with lutetium-177 dotatate can be used safely in patients with neuroendocrine neoplasm carcinoid heart valve disease and if there is associated survival advantage by reducing overall exposure of the valves to high doses of vasoactive peptides. Method: Retrospective case notes review was performed on 18 neuroendocrine neoplasm patients (mean 60 years), who underwent heart valve surgery between 2003 and 2017 for carcinoid heart valve disease, 9 of whom received peptide receptor radiotherapy in addition to surgery. Results: All patients were treated with somatostatin receptor antagonists and underwent cardiac valvular surgery (mean two valves replaced) and three benefitted from additional coronary bypass grafting. Nine patients underwent surgery alone: in this group, the time from surgery to progression was 14 months (mean; SD 13.5 months). Nine were treated with peptide receptor radiotherapy in addition to surgery. Six underwent surgery with peptide receptor radiotherapy on progression. Time to progression from surgery to first peptide receptor radiotherapy was mean 25.1 months (SD 23.6 months). No patients developed peritreatment cardiac complications. There were no deaths within the 30-day postoperative period. Average time from surgery to last follow-up/death was 41 months (6–79) in the surgery + lutetium group and in the surgery only group 17 months (1–24). Nine patients died, five in the surgery + lutetium group and four in the surgery only group, all at greater than 1-year postsurgery. Discussion: Peptide receptor radiotherapy is safe in the setting of Carcinoid valvular heart disease in patients with controlled heart failure, PPRT can be use in the pre- and post-valve surgery period. There appears to be a survival benefit of having peptide receptor radiotherapy. Further evidence for peptide receptor radiotherapy in the neoadjuvant setting prior to cardiothoracic surgery is required.