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Overall survival plateaus at 3 years for ipilimumab-treated melanoma patients

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A closer look at ipilimumab benefits

Dr. Schadendorf and his associates demonstrate a plateau in the survival curve of ipilimumab-treated patients beginning at about 3 years and representing about 21% of the treatment group. The curve suggests that those who survive to 3 years are highly likely to have a good long-term outcome, which provides a strong motivating factor in the decision to consider ipilimumab treatment. While pooled data adds information far beyond individual trials, a major drawback lies in the loss of control data necessary to isolate the added benefit of the study drug.

An indirect comparison using historic control series, in this case a large cohort documented in the American Joint Committee on Cancer (AJCC) Melanoma Staging Database, can substitute for missing control data in the pooled analysis. Reviewing data for stage IIIc and IV patients, the overall survival Kaplan-Meier curves in this population also show a plateau, but much later than that reported for ipilimumab, at beyond 8 years.

The AJCC melanoma classification gives survival rates at 3, 5, and 10 years of 19%, 13%, and 9%, respectively. Comparison with ipilimumab data suggests that survival at 3 years is similar, but thereafter improves with ipilimumab by 10% over other treatments that were available at the time. This difference is similar to the percentage of patients who achieved objective responses with ipilimumab. Although assessing response rate and progression-free survival in patients treated with ipilimumab presents challenges, the long-term benefits of ipilimumab could be better ascertained if information on the number of patients in the 21% plateau who were disease free or stably maintaining response had been collected.

Evaluation of long-term benefits of ipilimumab should consider toxicities and costs, as it is one of the most costly systemic therapies used for cancer treatment. The phase III trial using the drug at 3 mg/kg demonstrated that the large majority of patients had no serious adverse effects. If older patients and those with advanced disease are candidates, then the 10%-15% of grade 3 or 4 adverse events may translate to hospitalization and added expense, putting health regulatory systems in the position to deny widespread use of the agent despite proven benefit.

As the first agent to benefit overall survival of patients with advanced melanoma, ipilimumab may pave the way to broader improvements in a larger proportion of patients by combining with targeted therapies, such as BRAF and MEK inhibitors, and other new immunotherapies, such as anti-PD-1 antibodies.

Dr. Antoni Ribas is an oncologist with the Jonsson Comprehensive Cancer Center, Los Angles, and Dr. Keith T. Flaherty is an oncologist with Massachusetts General Hospital Cancer Center, Boston. These remarks were part of an editorial accompanying the report (J. Clin. Oncol. 2015 Feb. 9 [doi:10.1200/JCO.2014.56.2736]). Dr. Ribas has an advisory role with Merck, Amgen, Novartis, GlaxoSmithKline, and Genentech/Roche. Dr. Flaherty has an advisory role with GlaxoSmithKline, Genentech/Roche, Novartis, and Merck.


 

FROM THE JOURNAL OF CLINICAL ONCOLOGY

References

Among patients with advanced melanoma who were treated with ipilimumab, about 20%-26% survived to 3 years, and these patients are likely to have a good long-term outcome, according to a pooled analysis of survival data published online Feb. 9 in the Journal of Clinical Oncology.

Investigators pooled data from ten prospective (including two phase III trials) and two retrospective studies with a total of 1,257 previously treated and 604 treatment-naive patients. At least 3 years after receiving ipilimumab, 254 patients were still alive, with a median follow up for this subset of 69 months. Around year 3, the Kaplan-Meier overall survival (OS) curve began to plateau and extended to 9.9 years for the longest survival follow-up.

“These results suggest that the majority of patients who reached this milestone time point had a low risk of death thereafter,” wrote Dr. Dirk Schadendorf and his associates (J. Clin. Oncol. 2015 Feb. 9 [doi:10.1200/JCO.2014.56.2736]).

Compared with patients who were previously treated, treatment-naive patients had a higher median overall survival (13.5 months [95% confidence interval, 11.9-15.4] vs. 10.7 months [9.6-11.4]) and higher 3-year-survival rates (26% [21%-30%] vs. 20% [18%-23%]). No definitive conclusion could be drawn from this observation, however, since nonrandomized subsets were used for this analysis. Subset analysis by dose showed similar median OS and 3-year survival rates for ipilimumab 3 mg/kg, 10 mg/kg, and other dosing regimens.

The researchers expanded the study to include overall survival (OS) data from 2,985 patients enrolled in a U.S. multicenter, open-label, expanded-access treatment protocol (EAP). This group included patients with poorer prognostic factors, some of whom were ineligible for clinical trials. The expanded group showed a lower median OS of 9.5 months and 3 year–survival rate of 21%, with the familiar OS curve plateau around 3 years that extended up to 10 years in some patients.

While this analysis only examined overall survival rates, individual ipilimumab studies that tracked patient responses to the drug have shown that some proportion of long-term survivors did not achieve a response. Identifying the specific disease characteristics of the long-term survivors will require further study.

“Considering the historic median OS of approximately 8-10 months and a 5-year survival rate of approximately 10% in advanced melanoma, the results presented herein are encouraging for patients diagnosed with this aggressive disease,” the authors wrote.

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