for people ages 18 years and up (full criteria)
at UC Irvine
study started
estimated completion
Ling Gao(uci)



This phase III trial studies how well pembrolizumab works compared to standard of care observation in treating patients with stage I-III Merkel cell cancer that has been completely removed by surgery (resected). Immunotherapy with monoclonal antibodies, such as pembrolizumab, may help the body's immune system attack the cancer, and may interfere with the ability of tumor cells to grow and spread.

Official Title

STAMP: Surgically Treated Adjuvant Merkel Cell Carcinoma With Pembrolizumab, a Phase III Trial



  1. To compare overall survival (OS) and recurrence free survival (RFS) as co-primary endpoints across the two arms.


  1. To evaluate adverse events. II. To evaluate distant metastasis free survival (DMFS). III. To evaluate the impact of radiation on clinical outcomes (OS, RFS, DMFS).

OUTLINE: Patients are randomized to 1 of 2 arms.

ARM A: Patients receive pembrolizumab intravenously (IV) over 30 minutes on day 1. Treatment repeats every 21 days for up to 17 cycles in the absence of disease progression or unacceptable toxicity. Patients may also undergo standard of care radiation therapy within 14 days of day 1, cycle 1.

ARM B: Patients receive standard of care observation for 17 cycles. Patients may also undergo standard of care radiation therapy within 14 days of day 1, cycle 1.

After completion of study treatment, patients are followed up every 6 months for 5 years.


Pathologic Stage I Merkel Cell Carcinoma AJCC v8 Pathologic Stage II Merkel Cell Carcinoma AJCC v8 Pathologic Stage IIA Merkel Cell Carcinoma AJCC v8 Pathologic Stage IIB Merkel Cell Carcinoma AJCC v8 Pathologic Stage III Merkel Cell Carcinoma AJCC v8 Pathologic Stage IIIA Merkel Cell Carcinoma AJCC v8 Pathologic Stage IIIB Merkel Cell Carcinoma AJCC v8 Carcinoma, Merkel Cell Carcinoma Pembrolizumab Best Practice Radiation Therapy


For people ages 18 years and up

Inclusion Criteria:

  • Patients must have an Eastern Cooperative Oncology Group (ECOG) performance status: 0, 1, or 2 (However, those patients with a performance state of 3 because they are wheel chair bound due to congenital or traumatic events more than one year before the diagnosis of Merkel cell carcinoma are eligible).
  • Women must not be pregnant or breast-feeding due to the unknown effects of the study drug in this setting. All women of childbearing potential must have a blood test or urine study within 2 weeks prior to registration to rule out pregnancy. A female of childbearing potential is any woman, regardless of sexual orientation or whether they have undergone tubal ligation, who meets the following criteria: 1) has achieved menarche at some point, 2) has not undergone a hysterectomy or bilateral oophorectomy; or 3) has not been naturally postmenopausal (amenorrhea following cancer therapy does not rule out childbearing potential) for at least 24 consecutive months (i.e., has had menses at any time in the preceding 24 consecutive months).
  • Women of childbearing potential, and sexually active males, on Arm A MK-3475 (pembrolizumab must use accepted and effective method(s) of contraception or abstain from sex from time of registration, while on study treatment, and continue for 120 days after the last dose of study treatment. For patients on Arm B only receiving radiation therapy, contraception use should be per institutional standard.
  • Patient must have a histological confirmation of diagnosis of Merkel cell carcinoma (MCC), pathologic stages (American Joint Committee on Cancer [AJCC] version 8) I-IIIb.
  • Stage I patients with negative sentinel lymph node biopsy are ineligible. Patients who have a positive biopsy or for whom no biopsy was done are eligible.
  • Patients with distant metastatic disease (stage IV) are not eligible.
  • The primary tumor must have grossly negative margins. (Microscopically positive margins are allowed).
  • Cancers of unknown primary that have regional disease only can be included.
  • Complete nodal dissection is not required for eligibility.
  • Patients with all macroscopic Merkel cell carcinoma (either identified by physical exam or imaging) have been completely resected by surgery within 16 weeks before registration.
  • All patients must have disease-free status documented by a complete physical examination and conventional imaging studies within 8 weeks prior to registration.
  • Patient may not have a history of distant metastatic disease.
  • NOTE: Loco-regional recurrent disease is acceptable, as long as this is not metastatic (prior surgery with or without radiation therapy is acceptable).
  • For patients with initial presentation of Merkel cell carcinoma, patient must have no previous systemic therapy or radiation therapy prior to surgery for Merkel cell carcinoma and cannot have completed adjuvant radiation therapy for Merkel cell carcinoma more than 6 weeks prior to registration. Patients actively undergoing radiation therapy or having completed adjuvant radiation therapy within 6 weeks of registration are eligible, as long as resection date is within 16 weeks of registration.
  • White blood count >= 2000/uL (within 4 weeks prior to randomization).
  • Absolute neutrophil count (ANC) >= 1000/uL (within 4 weeks prior to randomization).
  • Platelets >= 75 x 103/uL (within 4 weeks prior to randomization).

  • Hemoglobin >= 8 g/dL (>= 80 g/L; may be transfused) (within 4 weeks prior to randomization).
  • Creatinine =< 2.0 x upper limit of normal (ULN) (within 4 weeks prior to randomization).
  • Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) =< 2.5 x ULN (within 4 weeks prior to randomization).
  • Total bilirubin =< 2.0 x ULN, (except patients with Gilbert's syndrome, who must have a total bilirubin less than 3.0 mg/dL) (within 4 weeks prior to randomization).
  • Patients who are human immunodeficiency virus (HIV)+ with undetectable HIV viral load are eligible provided they meet all other protocol criteria for participation.
  • Patients with hepatitis B virus (HBV) or hepatitis C virus (HCV) infection are eligible provided viral loads are undetectable. Patients on suppressive therapy are eligible.
  • Patients must not be on active immunosuppression, have a history of life threatening virus, have had other (beside non-melanoma skin cancers, or recent indolent cancers e.g.: resected low grade prostate cancer) invasive cancer diagnoses in the last two years, or have had immunotherapy of any kind within the last 2 years.
  • Patients must not have a history of (non-infectious) pneumonitis that required steroids or has current pneumonitis.
  • Operative notes from patient's surgical resection must be accessible.


  • UC Irvine Health/Chao Family Comprehensive Cancer Center accepting new patients
    Orange California 92868 United States
  • Sutter Davis Hospital accepting new patients
    Davis California 95616 United States
  • California Pacific Medical Center-Pacific Campus accepting new patients
    San Francisco California 94115 United States
  • USC Norris Oncology/Hematology-Newport Beach accepting new patients
    Newport Beach California 92663 United States

Lead Scientist

  • Ling Gao (uci)
    Associate Physician, Dermatology


accepting new patients
Start Date
Completion Date
National Cancer Institute (NCI)
Phase 3
Study Type
Last Updated