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Pembrolizumab and Radiation Therapy for the Treatment of Metastatic Merkel Cell Carcinoma

Trial Status: Active

This phase II trial studies the side effects and how well pembrolizumab and radiation therapy work in treating patients with Merkel cell carcinoma that has spread to other places in the body (metastatic). 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. Radiation therapy uses high energy x-rays to kill tumor cells and shrink tumors. Giving pembrolizumab and radiation therapy may increase the benefit of pembrolizumab.

Inclusion Criteria

  • Histologically confirmed metastatic Merkel cell carcinoma
  • Patients are eligible if they have received no more than 3 prior systemic treatments, inclusive of systemic adjuvant therapy. This includes previously untreated patients
  • Subjects with brain metastases and/or carcinomatous meningitis are eligible providing they are neurologically stable (if systemic steroids are required, subjects should be stable on the lowest clinically effective dose, as steroids may interfere with the activity of immunotherapy if administered at the time of the first anti-PD-1/PD-L1 dose.)
  • Availability of tumor tissue (fresh or archival) for central pathology review
  • Must be at least 14 days since treatment with chemotherapy, biochemotherapy, surgery, or immunotherapy, and recovered (baseline or residual grade 1 toxicity) from any clinically significant toxicity experienced during treatment before the first dose of pembrolizumab therapy
  • Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1
  • Life expectancy of >= 16 weeks
  • Subjects must have measurable disease according to Response Evaluation Criteria in Solid Tumors (RECIST) version (v) 1.1, and have baseline (screening/baseline) radiographic images, (e.g. computed tomography [CT], positron emission tomography [PET] CT or magnetic resonance imaging [MRI] brain, chest, abdomen, pelvis, to be determined by the attending physician) within 4 weeks of confirmation of eligibility and within 6 weeks before the initiation of pembrolizumab therapy
  • White blood count (WBC): >= 2000/uL (~ 2 x 10^9/L)
  • Absolute neutrophil count (ANC): >= 1000/uL (~ 1 x 10^9/L)
  • Platelets: >= 50 x 10^3/uL (~ 50 x 10^9/L)
  • Hemoglobin: >= 8 g/dL
  • Calculated creatinine clearance greater than 30 mL/min
  • Aspartate aminotransferase (AST)/alanine aminotransferase (ALT): Less than 2.5 x upper limit of normal (ULN) for subjects without liver metastasis, less than 5 times ULN for liver metastases
  • Bilirubin: less than 3.0 x ULN (except for subjects with Gilbert’s syndrome, who must have a total bilirubin of less than 3.0 mg/dL)
  • Non-clinically significant laboratory abnormalities such as lipase elevation would not be an exclusion
  • No known active or chronic infection with human immunodeficiency virus (HIV), hepatitis B, or hepatitis C, or active infection requiring systemic antibiotics. Testing for the above is not required unless clinically suspected
  • At least one measurable site of disease (>= 10 mm as per RECIST v1.1 except for lymph nodes that must be 15 mm or greater on the short axis) outside of the planned palliative radiation therapy field
  • Require radiation therapy for palliation of symptoms or to prevent local progression of disease and associated complications and/or symptoms from metastases
  • Women of childbearing potential (WOCBP) must be using an adequate method of contraception to avoid pregnancy throughout the study (and for up to 26 weeks after the last dose of investigational product) in such a manner that the risk of pregnancy is minimized * WOCBP include any female who has experienced menarche and who has not undergone successful surgical sterilization (hysterectomy, bilateral tubal ligation, or bilateral oophorectomy) or is not postmenopausal. Post-menopausal is defined as: ** Amenorrhea >= 12 consecutive months without another cause, or ** For women with irregular menstrual periods and on hormone replacement therapy (HRT), a documented serum follicle stimulating hormone (FSH) level > 35 mIU/mL * Women who are using oral contraceptives, other hormonal contraceptives (vaginal products, skin patches, or implanted or injectable products), or mechanical products such as an intrauterine device or barrier methods (diaphragm, condoms, spermicides) to prevent pregnancy, or are practicing abstinence or where their partner is sterile (e.g., vasectomy) should be considered to be of childbearing potential. WOCBP must have a negative serum or urine pregnancy test (minimum sensitivity 25 IU/L or equivalent units of human chorionic gonadotropin [HCG]) within 1 week prior to the start of investigational product
  • Men of fathering potential must be using an adequate method of contraception to avoid conception throughout the study (and for up to 26 weeks after the last dose of investigational product) in such a manner that the risk of pregnancy is minimized

Exclusion Criteria

  • WOCBP who are unwilling or unable to use an acceptable method to avoid pregnancy for the entire study and for up to 26 weeks after the last dose of investigational product
  • Women who are pregnant or breastfeeding
  • Women with a positive pregnancy test on enrollment or before investigational product administration
  • Subjects on any other systemic therapy for cancer, including any other experimental treatment within 2 weeks of scheduled first dose of pembrolizumab
  • Prior treatment with an anti-PD-1/PD-L1 antibody if treatment failure was due to adverse events (AEs). If a subject was discontinued from the prior anti-PD-1/PD-L1 treatment due to an AE or serious adverse event (SAE), regardless of the type of event, that discontinuation constitutes an exclusion criterion. If AEs were serious enough to require a subject’s withdrawal from prior treatment, the subject should be excluded from this study. The exception to the above are non-clinically significant immune-related laboratory abnormalities – these are not automatic exclusions – e.g. asymptomatic elevated amylase; responsiveness to steroids. In situations above – e.g. non-clinically significant immune-related laboratory abnormalities, each case will be considered individually and a decision made by the study team
  • A history of AEs with prior interleukin (IL)-2 or interferon will not preclude subjects from entering the current study
  • Poorly controlled autoimmune disease is excluded. Well controlled autoimmune disease (e.g. well controlled rheumatoid arthritis [RA]) will be assessed by the study team and a decision made regarding eligibility based on the degree of immunosuppression and severity of symptoms
  • Any subject who has a life-threatening condition that requires high-dose immunosuppressant(s). Steroid doses greater than 20 mg/day will exclude the patient from participation in the trial.
  • Presence of known hepatitis B or hepatitis C infection, regardless of control on antiviral therapy
  • Subjects who have another active, concurrent, malignant disease are not eligible, with the exception of subjects with adequately treated basal or squamous cell skin cancer, superficial bladder cancer, carcinoma in situ of the cervix, or other cancers that are in remission/not measurable. Patients will be excluded if they have any known additional malignancy that requires active treatment while on treatment for Merkel cell carcinoma
  • Bilirubin/total bilirubin 3 or more x ULN unless conjugated bilirubin is less than or equal to the ULN
  • Evidence of symptomatic interstitial lung disease or symptomatic active, noninfectious pneumonitis
  • Participants with impaired cardiac function or clinically significant cardiac disease such as unstable angina/uncompensated heart failure, uncontrolled symptomatic arrhythmia
  • Active autoimmune disease requiring systemic T-cell immunosuppression
  • Chronic or current active infectious disease requiring systemic antibiotics, antifungal, or antiviral treatment. This exclusion does not include prophylactic antibiotics or topical antibiotics
  • Known hypersensitivity to another monoclonal antibody, which cannot be controlled with standard measures (e.g. antihistamines and corticosteroids)
  • Any condition that would, in the investigator’s judgment, interfere with full participation in the study
  • Prior immune related AEs not meeting the conditions above
  • Prisoners or subjects who are involuntarily incarcerated
  • Subjects with acute or poorly controlled psychiatric illness or subjects who are compulsorily detained for physical (e.g., infectious disease) illness, with the exception of patients that are well supported and able to participate (e.g. paraplegia from a motor vehicle accident)
  • Any underlying medical or psychiatric condition that, in the opinion of the investigator, could make the administration of anti-PD-1/PD-L1 hazardous or could obscure the interpretation of adverse events
  • Any live vaccine therapy for up to 4 weeks before or after any dose of immunotherapy on this trial
  • Any investigational agents within 2 weeks of scheduled first dose of pembrolizumab


Palo Alto
Stanford Cancer Institute Palo Alto
Status: ACTIVE
Contact: Susan J. Knox
Phone: 650-725-2720


I. To assess the safety of combining anti-PD-1/PD-L1 blockade with palliative radiation therapy in patients with stage IV Merkel cell carcinoma.

II. To assess the efficacy of combining anti-PD-1/PD-L1 blockade with palliative radiation therapy in patients with stage IV Merkel cell carcinoma.


I. Assessment of overall survival and disease control rate/duration of response (complete response [CR], partial response [PR], stable disease [SD], immune-relate [ir]CR, irPR, irSD).


I. Mutational burden/microsatellite instability (MSI) analysis.

II. Measurement of polyomavirus in the blood.

III. Immune response assays at baseline, 2 weeks (+/- 1 weeks) and 8 weeks (+/- 1 weeks) after radiation therapy.

IV. Possible tumor biopsy studies.


Patients receive standard of care pembrolizumab intravenously (IV) over 30-60 minutes on day 1. Cycles repeat ever 3 weeks in the absence of disease progression or unacceptable toxicity. Patients also undergo radiation therapy 2-4 weeks after the fourth dose of pembrolizumab (between cycles 1 and 2).

After completion of study treatment, patients are followed up at 2-4 weeks, every 3 months for 2 years, then even 6 months for 3 years.

Trial Phase Phase II

Trial Type Treatment

Lead Organization
Stanford Cancer Institute Palo Alto

Principal Investigator
Susan J. Knox

  • Primary ID SKIN0047
  • Secondary IDs NCI-2019-05356, IRB-50888
  • ID NCT03988647