NEW TECHNOLOGIES IN RADIOTHERAPY FOR PROSTATE CANCER: FEASIBILITY, DOSIMETRIC ASPECTS AND CLINICAL RESULTS IN PATIENTS WITH AT LEAST 5-YEAR FOLLOW-UP

Background/Aim: Radiotherapy (RT) for prostate cancer has been constantly evolving over the last few decades, improving overall survival, cancer-specific and time progression of the disease. Different studies have shown a strong association between survival and RT doses (≥76 Gy). Advanced RT techniques such as modulated intensity (IMRT) and modulated intensity dynamic volumetric therapy (VMAT) facilitate and allow higher doses, minimizing the side effects on healthy surrounding tissues. Patients and Methods: A total of 261 prostate cancer patients referred to our institution for radical treatment, from January 2010 to December 2014, have been reviewed. Dosimetric comparison between IMRT and VMAT was made to evaluate the constraints (dose limits) for the organs at risk (OARs) in the district: the rectum, the bladder, the femoral heads, and the penile bulb. In addition, toxicity was assessed (according to CTCAE version 4.02 scale), progression-free survival (PFS) and overall survival (OS). Progression disease has been evaluated from a clinical point of view, through laboratory and radiological examinations. Results: Patients (49 at low-risk, 101 at intermediate-risk, and 111 at high-risk) were treated with radical RT for a total dose of 80 Gy (the pelvis was included in the volume of treatment in 57 patients). Of those, 208 were treated with IMRT technique and 53 with VMAT technique. Average age of patients was 72 years (range=42-86 years). Median PSA was 7.47 ng/ml and the minimum follow-up was 30 months. Dosimetric data showed that VMAT technique achieved better compliance with constraints for OARs, reducing the percentage of patients that deviated from dose limits. No patient exhibited Grade 2 Gastrointestinal (GI) and Genitourinary (GU) toxicity. G2 GI and G2 GU toxicity was reported in 13.5% and 5.7% of patients, respectively, at 5 years. PFS at 5 years was 82% for low- and intermediate- risk patients and 81% for high-risk patients. At 5 years, OS of the entire cohort was 93.2%. OS of the population by risk class stratification, at 5 years, can be summarized as follows: at 100% low-risk; in the intermediate-risk of 90% and in the high-risk of 93%. Conclusion: Reviewing our patients with at least 5-year follow-up, low acute and late toxicity was observed. This evidence could support the adoption of further dose escalation mainly in high-risk patients.