Radiotherapy to Control Limited Melanoma Progression Following Ipilimumab

Durable local control of irradiated cancer and distant abscopal effects are presumably immune mediated. To evaluate the role of radiotherapy (RT) for limited progression after anti-CTLA4 checkpoint inhibition, medical records of all patients with surgically incurable stage III or IV melanoma from a single institution who received ipilimumab as first-line immunotherapy and subsequent RT were reviewed. Sixteen patients who received RT to all sites of limited melanoma progression were analyzed. Eight patients with an incomplete initial response to ipilimumab received RT to new or progressive disease, whereas the remaining 8 patients with a complete initial response to ipilimumab received RT to sites of subsequent recurrence. The median interval from ipilimumab initiation to start of RT was 30 weeks (range, 15-130 wk), a timeframe where delayed response to ipilimumab is rare. The RT dose was predominantly 30 Gy in 5 fractions (41%) or 36 Gy in 6 fractions (26%). Brain radiation was limited to stereotactic radiosurgery in a single patient. The median local control with RT was 31.4 months. The median disease control was 18.7 months, defined as the interval from completion of RT to the start of additional systemic therapy known to impact survival (anti-programmed death-1 or targeted BRAF therapy), hospice enrollment, or death. The overall survival at 1 and 2 years was 87% and 61%, respectively. Seven patients (44%) had no evidence of melanoma at median follow-up of 29.5 months since completion of RT with no additional therapy. This series supports use of RT to limited sites of progression following ipilimumab as an alternative to other systemic treatments such as anti-programmed death-1 antibodies.