Purpose: To determine the planning results and acute toxicity after hypofractionated intensity-modulated arc radiotherapy and androgen deprivation for lymph node metastasized (Stage N1) prostate cancer.
Methods and materials: A total of 31 patients with Stage T1-T4N1M0 prostate cancer were treated with intensity-modulated arc radiotherapy and 3 years of androgen deprivation as primary treatment. The clinical target volume (CTV(p)) was the prostate and seminal vesicles. Elective lymph node areas ((e)) were delineated and expanded by 2 mm to create the CTV(e). The planning target volumes (PTV(p) and PTV(e)) were created using a three-dimensional expansion of the CTV(p) and CTV(e), respectively, of 7 mm. A median dose of 69.3 Gy and 50 Gy was prescribed to the PTV(p) and PTV(e) respectively, to be delivered in 25 fractions. Upper and lower gastrointestinal toxicity was scored using the Radiation Therapy Oncology Group toxicity and radiotherapy-induced lower intestinal toxicity scoring system. Genitourinary toxicity was scored using a combined Radiation Therapy Oncology Group, LENT-SOMA (late effects normal tissue-subjective, objective, management, analytic), and Common Toxicity Criteria toxicity scoring system.
Results: The median follow-up time was 3 months. The mean prescription dose to the CTV(p) and PTV(p) was 70.4 Gy and 68.6 Gy, respectively. The minimal dose to the CTV(e) and PTV(e) was 49.0 Gy and 47.0 Gy, respectively. No acute Grade 2 or greater gastrointestinal toxicity occurred. Fourteen patients developed acute Grade 2 lower gastrointestinal toxicity. Acute Grade 3 and 2 genitourinary toxicity developed in 2 and 14 patients, respectively.
Conclusion: The results of our study have shown that hypofractionated intensity-modulated arc radiotherapy as primary therapy for N1 prostate cancer is feasible with low toxicity.