Immunotherapy with Libtayo Prolongs Survival in Patients with Metastatic Cutaneous Squamous-Cell Carcinoma

New results of a study presented at the 2020 annual meeting of the American Society of Clinical Oncology (ASCO) show that use of immunotherapy prolongs survival for patients with advanced or metastatic (spreading) cutaneous squamous-cell carcinoma (CSCC). At the virtual ASCO meeting, Danny Rischin, MD, Director of the Department of Medical Oncology at Peter Mac-Callum Cancer Centre in Victoria, Australia, discussed the newly released long-term results of an ongoing study of patients with CSCC who received immunotherapy with the anti-PD-1 inhibitor Libtayo (cemiplimab).

CSCC, or skin cancer, is the second most common cancer in the United States, Dr. Rischin said. In most cases, skin cancer is removed by surgery or by radiotherapy, but surgery is not an option in patients with advanced or metastatic CSCC. Many patients with this type of cancer are diagnosed at a late stage, at which point the cancer is already locally advanced or metastatic and can no longer be treated with curative surgery or radiotherapy.

Information from previous studies with other types of therapies, such as chemotherapy or with EGFR inhibitors, for skin cancer showed that the average survival in patients with advanced or metastatic CSCC is about 15 months, according to Dr. Rischin.

First Immunotherapy for Skin Cancer

Based on the initial analysis of this phase 2 clinical trial, in 2018 Libtayo was approved by the FDA for the treatment of patients with advanced or metastatic CSCC. It is the first and only immunotherapy approved for patients with advanced or metastatic CSCC. Libtayo is a monoclonal antibody to the PD-1 receptor. By blocking the PD-1 pathway, the drug helps the body’s immune system fight cancer cells.

The new 3-year results of this phase 2 clinical trial showed a response rate of 46.1% to Libtayo therapy in patients with advanced CSCC who have continued to receive this immunotherapy.

Danny Rischin, MD

“This analysis of Libtayo demonstrates increasing and impressive duration of response. Duration of response and overall survival were considerably longer than what has previously been described with other agents,” said Dr. Rischin.

Increased Survival

In the initial analysis of this study, after nearly 16 months of treatment with Libtayo, the average duration of survival was not reached, meaning that patients were still responding to therapy. Now the new analysis includes data for 3 years of follow-up that evaluated the impact of 3 years of Libtayo treatment on survival and on the rate of patients with advanced or metastatic CSCC who have continued to respond to this treatment.

The study included 193 patients who were divided into 3 groups. Patients in group 1 had metastatic CSCC, and patients in group 2 had locally advanced disease; groups 1 and 2 received Libtayo every 2 weeks. The patients in group 3 had metastatic CSCC and received Libtayo every 3 weeks.

In group 1 in the original analysis in 2018, the rate of complete responses (no sign of cancer) was 6.8%, but a later analysis after an additional 1 year of follow-up, the complete response rate increased to 16.9%. And in the current analysis with 1 additional year of follow-up reported at the 2020 ASCO meeting, the response rate increased to 20.3%, showing improved survival with longer-term use of immunotherapy.

In group 2, no complete responses were seen at the original analysis, but at the additional 1-year follow-up, the complete response rate was 12.8%, which remained unchanged in this new analysis. In group 3, the complete response rate increased from 5.4% in the original analysis to 16.1% in this new 3-year follow-up analysis.

“The 3-year follow-up data demonstrate significant long-term outcomes with Libtayo, which is now standard-of-care for patients with advanced CSCC in many countries,” said Dr. Rischin.

“The Libtayo data on duration of response and overall survival provide new insights into the longer-term treatment of advanced CSCC….It is exciting to see the number of complete responses increase with longer follow-up, which reinforces the potential ongoing benefit of Libtayo treatment in this aggressive skin cancer,” Dr. Rischin said.

Long Duration of Response

Among patients who had a response, the responses lasted 6 months or more in 91% of the patients, and the estimated response rate for patients who are continuing to respond to treatment is 83.6%.

In addition, those who responded to Libtayo therapy did so rather quickly. The time to response was 2 months in 46.1% of patients, and an additional 32.6% of patients had a response within 2 to 4 months. Among 89 of the patients with a response to therapy, the average time to a complete response was 11.2 months, according to Dr. Rischin.

The estimated average time without disease progression in all patients receiving Libtayo was 18.4 months, and the average overall survival has not been reached for the total patient population in the study, meaning that many patients are still responding to therapy 3 years after starting treatment with this drug.

“This analysis indicates an increasing, clinically meaningful duration of response with Libtayo,” Dr. Rischin said.

Side Effects

Like all therapies, treatment with Libtayo is associated with side effects, and most (99.5%) patients in the study had at least 1 side effect related to the treatment. However, most of the side effects were not severe (grades 1 and 2), and very few patients stopped therapy with this immunotherapy.

No new side effects were seen in the 3-year follow-up period, and no deaths were reported with this therapy, Dr. Rischin concluded.