Hypofractionated Intensity-Modulated Arc Therapy for Lymph Node Metastasized Prostate Cancer

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.

N1 prostate cancer, Intensity-modulated arc therapy, IMAT, Hypofractionation, Acute toxicity