High-dose radiotherapy with helical tomotherapy and long-term androgen deprivation therapy for prostate cancer: 5-year outcomes

We aimed to examine outcomes of high-dose radiotherapy with helical tomotherapy (HT) and long-term androgen deprivation therapy (ADT) for T1-4N0M0 prostate cancer. A total of 391 patients treated with HT between June 2006 and December 2013 were included in this retrospective study. All patients received neoadjuvant ADT for a median duration of 10 months followed by HT at a median dose of 78 Gy [interquartile range (IQR) 78-78]. The times of median adjuvant and total ADT were 19 and 27 months (IQR 20-31), respectively. The risk stratification followed the 2015 National Comprehensive Cancer Network criteria. Biochemical disease-free survival (bDFS) followed the Phoenix definition. Toxicity was scored according to the Radiation Therapy Oncology Group morbidity grading scale. Median follow-up from HT start was 60 months (IQR 42-81). Five-year bDFS rates for low-, intermediate-, high-, and very-high-risk groups were 100, 98.2, 97.7, and 87.9 %, respectively. We observed clinical relapse in nine very-high-risk patients and one high-risk patient, resulting in a 5-year clinical relapse-free survival of 100, 100, 99.4, and 91.7 %, respectively, for each risk group. Three patients died of prostate cancer, resulting in a 5-year prostate cancer-specific survival of 99.6 %. The late grade 2 or higher gastrointestinal and genitourinary toxicities were 9.7 and 10.7 %. No cardiovascular fatal events were observed. This report confirmed the excellent outcomes with acceptable late toxicities with the combination of HT and long-term ADT. Longer follow-up is crucial to further determine the treatment effect and toxicity.