Trial results for pembrolizumab (Keytruda) in patients with anaplastic cancer of the thyroid (ATC) were posted on ClinicalTrials.gov on 2026-03-23. The Phase II IMPAACT trial (NCT05059470) reported a median disease-free survival (DFS) of 0.67 months in one cohort.
Background
Pembrolizumab (Keytruda) is an immunotherapy drug. This trial investigated its use in the adjuvant setting for anaplastic cancer of the thyroid (ATC), specifically in patients with stage IVB disease localized to the neck.
Trial design
The Phase II IMPAACT trial (NCT05059470) was an open-label, single-center study investigating adjuvant pembrolizumab after external beam radiation to the primary tumor in patients with stage IVB anaplastic cancer of the thyroid (ATC) localized to the neck. The trial enrolled 6 participants and was ultimately terminated. The study aimed to estimate the median progression-free survival (PFS).
Key results
The trial reported the median disease-free survival (DFS) for patients in Cohort 3. For this group, which received surgery, external beam radiation, and/or concomitant chemotherapy followed by adjuvant pembrolizumab, the median DFS was 0.67 months.
What this means
The reported median disease-free survival of 0.67 months in Cohort 3 suggests limited efficacy for adjuvant pembrolizumab in this specific population of patients with stage IVB anaplastic thyroid cancer. The termination of the trial, with only 6 participants enrolled, further indicates that the study did not proceed as initially planned, likely due to insufficient benefit or other factors.
Source
The information regarding these trial results was obtained from ClinicalTrials.gov, a public database of clinical studies. The results for study NCT05059470, titled "IMRT Followed by Pembrolizumab in the Adjuvant Setting in Anaplastic Cancer of the Thyroid (IMPAACT): Phase II Trial Adjuvant Pembrolizumab," were posted on 2026-03-23 on clinicaltrials.gov.