Improving Radiotherapy for Bladder Cancer: an Opportunity to Integrate New Technologies

Abstract

Despite data to support the use of radiotherapy as a radical treatment option for muscle invasive bladder cancer, its role has not been universally adopted. Historical series, which are subject to case selection bias, issues of stage migration (Will Rogers effect) and the use of outdated radiotherapy techniques, report inferior outcomes for radiotherapy compared with cystectomy [1,2]. More recent series, however, report similar outcomes [3,4]. There has never been a randomised comparison (although this is now ongoing in the National Cancer Research Institute "SPARE" trial). Neoadjuvant chemotherapy and the use of concomitant chemotherapy have been studied with some evidence of improved outcomes [5,6]. Perhaps because of the perceived inferior outcomes, the technical delivery of radiotherapy for bladder cancer has typically received little attention. However, the challenges associated with treatment planning and delivery lend themselves to solutions offered by the emergence of new technologies. The goal for bladder radiotherapy, as with any other tumour site, must be to deliver an individualised treatment plan with the greatest possible accuracy, delivering the greatest possible dose to tumour without excessive normal tissue irradiation. In relation to bladder radiotherapy, the greatest obstacle to achieving this is inter-fraction organ motion: many studies have shown that unpredictable changes in bladder filling occur throughout the course of treatment, to the extent that geographical miss occurs, despite margins of 1.5e2 cm around the whole bladder [7e9]. Intra-fraction motion is thought to be a lesser issue [10], but radiation oncologists need to be aware of both for the potential of movement due to changes in rectal distension, but also due to bladder filling during treatment administration. It is now possible with a variety of solutions to document bladder volume and target position before each fraction, assess coverage and compensate for day-to-day variation by adaptive planning. Integrating these technologies and techniques should permit a more accurate, individualised treatment with each fraction and permit further studies to improve outcomes from bladder radiotherapy.