From March 19-22,the Society of Gynecological Oncology (SGO) held its 2021 Annual Meeting on Women’s Cancer. Because of COVID-19, the event was held virtually. During the meeting, researchers presented an abstract on data from the Phase 2 KEYNOTE-158 clinical trial evaluating pembrolizumab for patients with vulvar squamous cell carcinoma, a form of vulvar cancer. According to the Cancer Network, the study results found that patients with previously treated cancer still had sustained responses to the treatment.

Pembrolizumab

What is pembrolizumab? Also known as Keytruda, Cancer Research UK describes pembrolizumab as:

a type of immunotherapy [which] stimulates the body’s immune system to fight cancer cells. Pembrolizumab targets and blocks a protein called PD-1 on the surface of certain immune cells called T-cells, [which] triggers the T-cells to find and kill cancer cells.

Outside of vulvar cancer, pembrolizumab is also used to treat non-small cell lung cancer (NSCLC), melanoma, Hodgkin’s lymphoma, and bladder cancer. The therapy is administered intravenously.

The Research

Patients who enrolled in the clinical trial were 18 or older. During the study, patients with previously treated vulvar cancer (that did not respond to treatment) received 20mg pembrolizumab every 3 weeks. The treatment continued until the patient had either:

• Experienced cancer progression
• Reached a level of unacceptable toxicity
• Finished 35 treatment cycles

Over a 1-year period, patients underwent tumor imaging every 9 weeks. For additional follow-up, imaging was performed every 12 weeks. Findings from the study included:

• There was an overall clinical benefit rate of 28.7%. This included 11% confirmed responses and 18% stable cancer.
• Patients treated with pembrolizumab saw sustained, durable responses. Overall, the response rate lasted for an average of 20.4 months following treatment.
• Patients with PD-L1 negative tumors had a slightly higher response rate than patients with PD-L1 positive tumors.
• 2.1 months was the average progression-free survival rate for the entire enrolled group. 50.5% of treated patients were also alive 6 months following treatment, with 14% alive after 2 years.
• Pembrolizumab did not significantly reduce tumor size.

Generally, pembrolizumab was found to be relatively safe and well-tolerated. Side effects and adverse reactions included:

• Appetite loss
• Rash
• Diarrhea
• Nausea
• Abnormal physical weakness and/or lack of energy
• Hypo- or hyperthyroidism
• Fatigue
• Pneumonitis
• Colitis
• Vasculitis
• Pruritus (intense itching)

Unfortunately, the drug caused two fatalities. Ultimately, this was due to hepatitis.

Vulvar Cancer

There are two forms of vulvar cancer: vulvar melanoma and vulvar squamous cell carcinoma. In both cases, the cancer occurs on the vulva, or the outer surface of female genitalia. Vulvar melanoma is the more rare form, forming in pigment-producing cells. Alternately, vulvar squamous cell carcinoma makes up a majority of diagnoses and forms in thin, flat cells on the vulvar surface. Altogether, the cancer occurs in four stages. The first of which sees the cancer in a tumor somewhere between the vaginal opening and anus. However, by the final stage, vulvar cancer may spread throughout the body. Symptoms include:

• Constant and persistent itching
• Abnormal bleeding
• Skin thickening or changing colors
• A vulvar lump, sore, or wart-like bump(s)
• Vaginal and vulvar pain and tenderness

Treatment for vulvar cancer may include surgery, radiation, or chemotherapy. Early detection greatly improves patient outcomes.

Learn more about vulvar cancer here.