Phase II Trial of Serum Micro RNA-371 in Detecting Active Germ Cell Tumors in Patients with Suspected Regional Disease - (MAGESTIC Trial: MiRNA in Detecting Active Germ Cell Tumors in Early Suspected and MetastaTIC Disease Trial)

Inclusion Criteria

• * Primary tumor excised by radical inguinal orchiectomy and pathology consistent with GCT (seminoma or NSGCT) * Clinical stage of patient is either: ** Stage I pure seminoma OR stage I pure seminoma with isolated retroperitoneal relapse or Stage IIA/B pure seminoma ** Stage I NSGCT OR stage I NSGCT with isolated retroperitoneal relapse or Stage IIA/B NSGCT * Suspected retroperitoneal disease: Lymphadenopathy in the retroperitoneum with no lymph node > 3 cm in greatest dimension with no more than 2 nodes enlarged * Axial abdominal/pelvic imaging (CT or MRI) and chest imaging (x-ray, CT or MRI) within 3 months of enrollment if stage I patient * Axial abdominal/pelvic imaging (CT or MRI) and chest imaging (x-ray, CT or MRI) within 6 weeks of enrollment if stage II patient * MiRNA-371 level drawn within 1 year after orchiectomy for stage I patients * MiRNA-371 level drawn at any timepoint after orchiectomy for stage II patients * Retroperitoneal lymphadenopathy must be within an RPLND template * Biopsy of lymph node is not required, though if biopsy of the retroperitoneal node(s) was obtained, pathology must be consistent with GCT * Serum AFP, β-HCG, LDH (per the local laboratory assay) < 1.5 x lower normal level within 42 days (6 weeks) of enrollment * Age ≥ 16 years * Ability to understand and the willingness to sign a written informed consent

Exclusion Criteria

• * Second primary malignancy * History of receiving chemotherapy or radiotherapy * Patients receiving any other investigational agent (s) * Uncontrolled intercurrent illness including, but not limited to, ongoing or active infection, symptomatic congestive heart failure, unstable angina pectoris, cardiac arrhythmia, or psychiatric illness/social situations that would limit compliance with study requirements