Phase II trial of high dose stereotactic body radiation therapy for lymph node oligometastases

Lymph nodes are common sites of oligometastases for several primaries. Stereotactic body radiation therapy (SBRT) represents an effective treatment but no consensus exists regarding dose and fractionation. Aim of this trial was to evaluate safety and efficacy of high-dose SBRT. We included patients with 1 to 3 lymph node metastases. Primary end-point was safety, while secondary end-points were in-field local control (LC), out-field lymph nodal progression free survival (LPFS), distant metastasis free survival (DMFS), progression free survival (PFS) and overall survival (OS). 64 lesions in 52 patients were treated from 2015 to 2019. Most common primary tumor was genitourinary cancer (75%), in particular prostate cancer (65.4%). With a median follow-up of 24.4 months (range 3-49), treatment was very well tolerated, with only 4 (7.7%) patients reporting acute side effects, all classified as grade 1, in the form of pain, fatigue, nocturia and dysuria. No toxicity ≥ grade 2 were reported. Rates of LC at 1, 2 and 3 years were 97.9%, 82.1% and 82.1%. Male sex (HR 0.12, p value 0.014) was associated with improved LC. LPFS at 1, 2 and 3 years were 69.6%, 49.6% and 46.1%, respectively, and DMFS was 81.74%, 67.5% and 58.5%, respectively. Presence of lesions in other organs was correlated with inferior DMFS (HR 3.82, p = 0.042). PFS at 1, 2 and 3 years were 67.4%, 42.4% and 31.86%, respectively. OS at 1, 2 and 3 years were 97.3%, 94.2%, 84%, respectively and significantly correlated with in-field recurrence (HR 8.72, p = 0.000). Our prospective trial confirms safety and efficacy of SBRT in the management of lymph node metastases. Registered Clinical trial NCT02570399.