A Class Solution to Hypo-Fractionated Radiotherapy in HighRisk Localised Prostate Cancer Using 3-D CRT: A Case Study for Parirenyatwa Radiotherapy Centre

Abstract

Prostate cancer (PCa) is the fourth most common cancer in men worldwide. In Zimbabwe, it is the most prevalent cancer among men  leading to high mortality and morbidity. At present, radiation therapy is restricted to external beam as there are no facilities that offer  prostatic brachytherapy in the country. Conventional fractionation radiotherapy, where total doses of 78Gy are given in 39 fractions at  2Gy/fraction, five days per week, has been the treatment of choice for patients with localised disease. This regimen has been associated  with problems such as long waiting periods as well as increased mortality and morbidity due to undoubtedly long treatment periods.  Hypo-fractionation has been associated with better tumour control while offering convenience to patients. This option also increases  community accessibility, especially for resource-constrained nations like Zimbabwe with only two public institutions offering  radiotherapy. However, hypo-fractionation comes with the demand for greater conformity during treatment planning in order to reduce  radiotherapy complications. The aim of the study was to come up with the most appropriate treatment plan that can be adopted when dose escalation is considered in high-risk localised PCa using 3-Dimensional Conformal Radiotherapy (3-D CRT). A quantitative  retrospective observational study was done in a sample of ten (n=10) patients with localised high-risk prostate cancer T2b-T4N1M0. Previously acquired pelvic computed tomography (CT) images of patients treated at Parirenyatwa Group of Hospitals Radiotherapy and  Oncology Department were used. Nine (9) treatment plans were generated for each patient with different selected gantry angles from a  minimum of five fields to a maximum of nine fields. The plans were analysed quantitatively by using cumulative dose volume histograms  (DVHs); and qualitatively through slice-by-slice view of the volume. The research revealed that the three best treatment plans that  provided good planning target volume (PTV) coverage, organs at risk (OAR) sparing and were considered clinically feasible were, in order  of priority, plan 3 (direct anterior, 2 laterals and 2 posterior obliques); plan 8 (direct anterior, 2 laterals and 2 pairs of opposing obliques);  and plan 6 (2 laterals, 2 anterior obliques and 2 posterior obliques). With the employment of the three treatment planning techniques,  hypo-fractionation in prostate radiotherapy is a possibility. It was recommended that the findings of the study be used in research  studies of biological models to approximate the therapeutic index of hypo-fractionated radiotherapy (HFRT) of PCa on the Zimbabwean  population.