Stereotactic body radiotherapy in oligometastatic prostate cancer patients with isolated lymph nodes involvement: a two-institution experience

Stereotactic body radiotherapy (SBRT) is emerging as a treatment option in oligometastatic cancer patients. This retrospective study aimed to analyze local control, biochemical progression-free survival (b-PFS), and toxicity in patients affected by isolated prostate cancer lymph node metastases. Finally, we evaluated androgen deprivation therapy-free survival (ADT-FS). Forty patients with 47 isolated lymph nodes of recurrent prostate cancer were treated with SBRT. Mostly, two different fractionation schemes were used: 5 x 7 Gy in 23 (48.9 %) lesions and 5 x 8 Gy in 13 (27.7 %) lesions. Response to treatment was assessed with periodical PSA evaluation. Toxicity was registered according to RTOG/EORTC criteria. With a mean follow-up of 30.18 months, local control was achieved in 98 % of the cases, with a median b-PFS of 24 months. We obtained a 2-year b-PFS of 44 % with 40 % of the patients ADT-free at last follow-up (mean value 26.18 months; range 3.96-59.46), whereas 12.5 % had a mean ADT-FS of 13.58 months (range 2.06-37.13). Late toxicity was observed in one (2.5 %) patient who manifested a grade 3 gastrointestinal toxicity 11.76 months after the end of SBRT. Our study demonstrates that SBRT is safe, effective, and minimally invasive in the eradication of limited nodal metastases, yielding an important delay in prescribing ADT.