Hypofractionated, Dose Escalation Radiotherapy for High Risk Adenocarcinoma of the Prostate

In North America, around a quarter a million men are diagnosed with prostate cancer every year, and about 31,000 patients will die of their disease each year. Like other western countries, the incidence in Canada has increased due to an aging population and prostate specific antigen (PSA) screening. This has led to a significant demand on cancer care services for these patients. Prostate cancer patient with high risk features are more often treated with external beam radiation therapy (EBRT) plus two to three years of hormonal manipulation (luteinizing hormone-releasing hormone \[LHRH\] agonist). The most common radiation dose treatment for these patients is 74-78 Gy in 37-39 daily fractions of 180-200 cGy for a treatment length of 7.5 weeks. This fraction size is believed to offer the best balance between desired tumour kill and unwanted normal tissue injury. Larger fraction sizes of more than 250 cGy (hypofractionation) are usually avoided for curative therapy because late reacting normal tissues. However prostate cancer cells have a unique radiobiology characteristic that suggests that hypofractionated radiotherapy is more efficient at prostate tumour killing than standard fractionation is, and will produce equivalent tumour control with a lower total dose and a shorter overall treatment time. Improved target localization techniques and conformal radiation therapy technology have allowed for dose escalation and hypofractionated radiation delivery in these circumstances with minimal or no increased toxicities. This trial is designed to determine whether high risk prostate cancer patients can be safely treated with a dose escalation hypofractionated radiation therapy in 5 weeks as opposed to the usual 7-8 weeks. These patients will be randomized to either the usual 76 Gy in 38 fractions or 68 Gy in 25 fractions. 3D-Conformal Radiotherapy (3D-CRT) or Intensity Modulated Radiotherapy (IMRT) will be used to deliver the required radiation dose. Patients will also receive 28 months of androgen deprivation therapy (LHRH agonist). The primary outcome of the study is the acute and delayed toxicity and the secondary outcomes include biochemical failure, prostate specific mortality rate, bone metastases free survival, the prognostic and predictive value of several biological variables: presence of the PTEN deletion; expression of FoxP3 gene variants, topoisomerase 2α and cancer testis antigens; expression of X chromosome-linked micro-RNAs; presence of TMRSS2-ERG gene fusion and quality of life. It is planned to recruit 250 patients to this study.