Salvage extended field or involved field nodal irradiation in F-18-fluorocholine PET/CT oligorecurrent nodal failures from prostate cancer

{Purpose The concept of metastasis-directed therapy for nodal oligorecurrences with stereotactic body radiotherapy is increasingly accepted. Hence, the comparison between salvage extended field radiotherapy (s-EFRT) and salvage involved field radiotherapy (s-IFRT) in patients with F-18-fluorocholine (FCH) PET/CT+ nodal oligorecurrences from prostate cancer is worthy of investigation. Methods Patients with oligorecurrent nodes on FCH PET/CT treated with salvage radiotherapy between 2009 and 2017 in a single tertiary cancer centre were selected for this study. Patients treated with s-IFRT were compared with those treated with s-EFRT. Toxicities and times to failure (TTF) were compared between the two groups. Results The study included 62 patients with positive lymph nodes only who underwent FCH PET/CT for a rising PSA level after radical prostatectomy or radiotherapy. Of these patients, 35 had s-IFRT and 27 had s-EFRT. After a median follow-up of 41.8 months (range 5.9-108.1 months), no differences were observed in acute or late gastrointestinal and genitourinary toxicities of grade 2 or more between the two groups. The 3-year failure rates were 55.3% (95% CI 37.0-70.3%) in the s-IFRT group and 88.3% (95% CI 66.9-96.1%) in the s-EFRT group (p = 0.0094). In multivariate analysis of TTF, an interval of > 5 years was significantly correlated with better outcomes (HR = 0.33, 95% CI 0.13-0.86