Single-institution experience with ipilimumab in advanced melanoma patients in the compassionate use setting: lymphocyte count after 2 doses correlates with survival

Abstract

Background: : Ipilimumab is a monoclonal antibody that antagonizes cytotoxic T lymphocyte antigen-4, a negative regulator of the immune system. The authors report on advanced refractory melanoma patients treated in a compassionate use trial of ipilimumab at the Memorial Sloan-Kettering Cancer Center.

Methods: : Patients with advanced refractory melanoma were treated in a compassionate use trial with ipilimumab 10 mg/kg every 3 weeks for 4 doses. Those with evidence of clinical benefit at Week 24 (complete response [CR], partial response [PR], or stable disease [SD]) then received ipilimumab every 12 weeks.

Results: : A total of 53 patients were enrolled, with 51 evaluable. Grade 3/4 immune-related adverse events were noted in 29% of patients, with the most common immune-related adverse events being pruritus (43%), rash (37%), and diarrhea (33%). On the basis of immune-related response criteria, the response rate (CR + PR) was 12% (95% confidence interval [CI], 5%-25%), whereas 29% had SD (95% CI, 18%-44%). The median progression-free survival was 2.6 months (95% CI, 2.3-5.2 months), whereas the median overall survival (OS) was 7.2 months (95% CI, 4.0-13.3 months). Patients with an absolute lymphocyte count (ALC) > micro =1000/microL after 2 ipilimumab treatments (Week 7) had a significantly improved clinical benefit rate (51% vs 0%; P = .01) and median OS (11.9 vs 1.4 months; P < .001) compared with those with an ALC <1000/microL.

Conclusions: : The results confirm that ipilimumab is clinically active in patients with advanced refractory melanoma. The ALC after 2 ipilimumab treatments appears to correlate with clinical benefit and OS, and should be prospectively validated. Cancer 2010. (c) 2010 American Cancer Society.

Figure 1

Radiographic images of a patient with a complete response are shown. Representative images were obtained (A) at baseline, (B) after completing induction with 4 treatments of ipilimumab every 3 weeks, and (C) at 9 months (before the second dose of maintenance ipilimumab). The patient was alive at the time of last follow-up without evidence of disease recurrence, 11.2 months after the initiation of protocol therapy.

Figure 2

Changes in the absolute lymphocyte count (ALC) with ipilimumab therapy are shown. (A) The ALC of all patients at baseline and after 1 and 2 doses of ipilimumab is shown. (B) The change in ALC for each patient with therapy is shown.

Figure 3

Kaplan-Meier survival curves are shown stratified by the absolute lymphocyte count (ALC) at (A) baseline and after (B) the first and (C) second ipilimumab doses.