Reduced Intensity Radio-chemotherapy for Stage IIA/B Seminoma

Inclusion Criteria:

* Written informed consent according to ICH/GCP (International Council on Harmonization/Good Clinical Practice) regulations before registration and prior to any trial specific procedures
* Histologically confirmed classical seminoma treated with primary inguinal orchidectomy or partial orchidectomy
* Patients with a seminoma stage IIA or IIB, either newly diagnosed or recurrent after primary active surveillance, adjuvant carboplatin or radiotherapy for stage I disease. The tumor stage is pT1-4 cN1-2 cM0 according to UICC TNM 8th edition 2016. Patients with a recurrent seminoma stage IIA or IIB are only eligible in case of progression under active surveillance or recurrence after adjuvant carboplatin or radiotherapy for stage I disease
* Stage IIA, in patients with equivocal lymph node enlargement, needs to be confirmed with a repeated CT/MRI scan of the abdomen (suggested timeframe: 4 weeks after the previous scan) in order to rule out false positive lymph node enlargement.

Patients with a prior malignancy treated with curative intention are eligible if all treatment of that malignancy was completed at least 5 years before registration and the patient has no evidence of disease at registration. Less than 5 years is acceptable for malignancies with low risk of recurrence and/or no late recurrence. Patients with a germ cell neoplasia in situ (GCNIS) or contralateral localized treated seminoma are eligible

* Diagnostic CT or MRI or FDG-PET-CT of the chest, abdomen and pelvis within 28 days prior to registration, showing stage IIA/B disease. I.v. contrast medium has to be administered
* Age ≥ 18 years
* WHO performance status 0-2
* Baseline PRO questionnaires have been completed
* Adequate bone marrow function: neutrophil count ≥ 1.0 x 109/L, platelet count ≥ 100x 109/L
* Adequate renal function: creatinine clearance ≥ 60 ml/min calculated according to the CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) formula
* Patient agrees to use highly effective contraception and not to donate sperm or to father a child during trial treatment and during 12 months thereafter. Patient has been proposed sperm conservation.

Exclusion criteria

* Any other histological component than seminoma
* Elevated levels of Alpha-1-Fetoprotein AFP (≥ 2x ULN)
* Involved nodes (metastatic) in previously irradiated localizations in the abdomen or pelvis
* Any anti-cancer therapy after primary tumor resection in patients presenting with primary stage IIA/B seminoma
* Any serious underlying medical condition (i.e. current renal insufficiency, severe hepatic insufficiency, severe bone marrow dysfunction, tumor bleeding, major hearing defects) or serious co-morbidity which could impair the ability of the patient to participate in the trial (according to investigator's judgment)
* Any treatment in a clinical trial within 28 days prior to registration
* Any concomitant drugs contraindicated for use with the trial drugs according to the approved product information or contraindicated for use with radiotherapy
* Known hypersensitivity to trial drugs or to any component of the trial drugs
* Any other serious underlying medical, psychiatric, psychological, familial or geographical condition, which in the judgment of the investigator may interfere with the planned staging, treatment and follow-up, affect patient compliance or place the patient at high risk from treatment-related complications.

Additional German specific exclusion criteria - not to be considered for Swiss patients

* Patient who is dependent on the sponsor or the investigators according to ICH/GCP E6(R2), guideline
* Patient who has been committed to an institution by virtue of an order issued either by the judicial or the administrative authorities according to § 40a (2) AMG.