Checkpoint inhibitor treatment in patients with isolated in-transit melanoma metastases.

10070Background: In the context of multiple in-transit melanoma metastases without nodal involvement, a variety of treatment modalities have historically been employed including surgery, laser, isolated limb perfusion/infusion, intralesional interleukin-2, T-VEC and electrochemotherapy. Unfortunately, most patients treated with these modalities experience subsequent disease progression. While checkpoint inhibitors (CPI) are a standard of care for bulky unresectable stage III and for stage IV melanoma, patients with isolated in-transit metastases were rarely included in registration studies. There are anecdotal reports of lower response rates in these patients despite them having disease characteristics that would usually be associated with a good response. Methods: We report data from 11 retrospective patient cohorts treated at cancer centres across Europe who received CPI between 2016 and April 2019. All patients had multiple in-transit metastases without clinical or radiological evidence of nodal or distant disease. Disease response was assessed using CT, PET-CT or MRI depending on clinical indication. All patients had at least one prior resection of loco-regional relapsed disease and were deemed not curable by further surgery. Results: Sixty three patients meeting criteria were identified, 40 females and 23 males. Median age was 72 years and 54 (86%) patients had a normal lactate dehydrogenase (LDH). 19 (30%) patients had a BRAF mutation. At treatment initiation, the majority 55 (87.3%) received single agent PD-1 inhibitor, 7 (11.1%) combination ipilimumab + nivolumab and 1 (1.6%) received single agent anti-CTLA 4. The overall response rate was 62% for the full population. The response rate with anti-PD1 monotherapy was 59%. With a median FU of 23 months, the median PFS was 26 months, median OS not reached. OS estimates with 95% CI: 12 month - 93% (87-100%), 24 month - 88% (80-98%), 36 month - 80% (67-95%). Conclusions: The results show a high response rate to CPI in patients with in-transit metastases and support early treatment with CPI following identification of in-transit metastases not curable with surgery whilst disease characteristics remain favourable.