A REVIEW OF MONTE CARLO SIMULATION OF ORGANS AT RISK IN PROSTATE CANCER TREATMENT USING SPACER GEL IN NIGERIA

Abstract

In Nigeria, prostate cancer is a major burden in oncology due to its increasing incidence and mortality rates. The main curative treatment for localized disease is radiotherapy, but dose escalation required to achieve optimal tumour control is limited by the proximity of organs at risk (OARs) such as the rectum and bladder. The review examines the potential application of hydrogel spacers in prostate radiotherapy, the role that Monte Carlo (MC) simulation plays in accurate OARs dosimetry, the international evidence for the effectiveness of spacers, and the analysis of implementing feasibility within the Nigerian healthcare context. A narrative synthesis of peer-reviewed literature was conducted, focusing on hydrogel spacer applications, the MC dosimetry methodologies, the clinical outcomes from several trials executed in the settings of low- and middle-income countries, and infrastructure assessments of radiotherapy, in which specific emphasis was on Nigeria.  Hydrogel spacers in international randomized controlled trials have shown to achieve a separation of 10-15 mm between the prostate and rectum, reducing rectal V70 Gy by 60-80% and decreasing late grade ≥2 rectal toxicity from 5-15% to 1-5%. The accuracy of MC simulation provides superior accuracy in modeling dose perturbations at the tissue-spacer interface to a greater extent, with errors reduced from >10% to <2%. However, there are significant barriers to its implementation in Nigeria, which include the 10-15 functional linear accelerators available for the over 220 million population, which is <0.05 per million versus the recommended >4 million, prohibitive spacer costs >$5,000 per procedure, scarcity of treatment planning systems that are MC-capable, and drastic shortages of qualified medical physics personnel. While hydrogel spacers combined with MC-based planning offer proven improvements in the therapeutic ratio of prostate radiotherapy, a variety of significant infrastructure, financing, and human resource challenges restrict the immediate implementation of these in Nigerian healthcare. Strategic investments in radiotherapy infrastructure, training of professionals, and conducting context-specific research are essential for everyone to access these advancements.