Stereotactic Radiotherapy for the Treatment of Patients With Oligo-progressive Metastatic Renal Cell Carcinoma Receiving Vascular Endothelial Growth Factor Receptor Tyrosine Kinase Inhibitor: Data From the Real World

AIM: This retrospective observational study evaluated the role of hypo-fractionated stereotactic radiotherapy (SRT) in patients with oligo-progressive metastatic renal cell carcinoma (mRCC) treated with first-line oral tyrosine kinase inhibitors (TKI). Data on local control, delay of further progression, and safety are reported. PATIENTS AND METHODS: Between January 2010 and December 2016, 28 patients with mRCC who showed oligo-progressive disease while receiving first-line pazopanib were treated with hypofractionated SRT to progressive metastatic sites to delay the change of systemic therapy. First and second progression-free survival (PFS-1 and PFS-2) were recorded, as well as objective response and toxicity. RESULTS: After pazopanib therapy, nine partial remissions (32%), 12 stable disease (43%) and seven progressions (25%) were recorded. The median time to progression from first-line pazopanib until oligo-progression was 9.45 months (PFS-1 range=2-30 months). Seventeen patients (61%) showed progression at pre-existing tumor sites, and 11 patients (39%) showed the appearance of new metastases. Progression-free survival after radiation therapy was 4.55 months (PFS-2 range=1-11 months). PFS-1 plus PFS-2 was 14.0 months (range=3-41 months). Severe grade 3-4 toxicities were seen only occasionally. CONCLUSION: Patients with oligo-progressive mRCC treated with first-line pazopanib may benefit from hypo-fractionated high-dose SRT at progressing sites achieving a further increase in median progression-free survival. Further studies and prospective validation are required to establish if this minimally invasive approach may have a positive impact on overall survival and reported outcomes.