Rare cancers comprise about 20% of all cancers in the United States and Europe, according to recent estimates, but patients with rare cancers are vastly underrepresented in clinical trials.
Dr. Michael Wagner
Recently, there has been a focus on immune checkpoint blockade (ICB) in common cancer types. Since several rare tumor types share similar biologic features with the more common tumors, there is a need to test ICB in rare tumors, particularly because remissions with ICB can be durable.
Enter the DART trial, a phase 2, single-arm study of combinatorial ICB with ipilimumab plus nivolumab in patients with unresectable or metastatic rare cancers.
Results from DART were recently presented at the Society for Immunotherapy of Cancer’s 35th Anniversary Annual Meeting. Michael J. Wagner, MD, of the University of Washington, Seattle, reported results in patients with advanced or unresectable angiosarcoma, one of the rare tumor types included in DART.
About angiosarcomas
Angiosarcomas account for less than 3% of all adult soft-tissue sarcomas, according to a review published in The Lancet Oncology. Angiosarcomas may arise in any part of the body, especially the head and neck (27%), breast (19.7%), and extremities (15.3%). These cancers can be primary or secondary (i.e., associated with prior radiation therapy or chronic lymphedema).
Angiosarcomas are aggressive, difficult to treat, and confer high mortality. The tumors are responsive to chemotherapy, but responses are brief. The estimated 5-year survival rate for all patients with angiosarcoma, including those who present with localized disease, is 30%-40%.
According to Dr. Wagner, a subset of angiosarcomas are characterized by high tumor mutational burden (TMB) and COSMIC signature 7, a DNA mutational signature that is consistent with other cancers caused by ultraviolet light exposure.
The high TMB subset of angiosarcomas is comparable with other cancer types that are responsive to ICB. Indeed, patients with angiosarcoma treated with ICB have shown responses, according to research published in the Journal for Immunotherapy of Cancer. However, no prospective studies of ICB in angiosarcoma have been published.
About DART
The DART trial includes more than 50 cohorts of rare cancer subtypes. Patients receive IV ipilimumab at 1 mg/kg every 6 weeks and IV nivolumab at 240 mg every 2 weeks.
The primary endpoint is objective response rate, as assessed by RECIST v1.1. Secondary endpoints include progression-free survival, overall survival, stable disease at 6 months, and toxicity.
The trial has a two-stage design. Six patients are enrolled in the first stage, and, if at least one patient responds to treatment, an additional 10 patients are enrolled in the second stage.
If at least two responses are seen among the 16 patients enrolled, further study of ICB is considered warranted.
Results in angiosarcoma
Dr. Wagner reported on the 16 angiosarcoma patients enrolled in DART. Nine patients had cutaneous primary tumors, seven had noncutaneous primary tumors, and three patients had radiation-associated angiosarcoma of the breast or chest wall.
Patients had received a median of two (range, zero to five) prior lines of therapy.
Adverse events (AEs) were consistent with prior safety results of the ipilimumab-nivolumab combination. Three-quarters of patients experienced an AE of any grade. The most common AEs were transaminase elevation, anemia, diarrhea, fatigue, hypothyroidism, pneumonitis, pruritus, and rash.
A quarter of patients had a grade 3-4 AE, and 12.5% of AEs led to premature treatment discontinuation. There were no fatal AEs.
The ORR was 25%. Responses occurred in 4 of the 16 patients, including 3 of 5 patients with primary cutaneous tumors of the scalp or face and 1 of 3 patients with radiation-associated breast angiosarcoma.
Two of the four responses and one case of stable disease have persisted for almost a year, and these patients remain on treatment. To put these results into perspective, Dr. Wagner noted that responses to cytotoxic chemotherapy rarely last 6 months.
The 6-month progression-free survival rate was 38%. The median overall survival has not yet been reached.
Dr. Wagner concluded that the combinatorial ICB regimen employed in DART was well tolerated and had an ORR of 25% in angiosarcoma regardless of primary site. Per the criteria of the DART trial, further investigation of ICB in angiosarcoma is warranted.