# Seminoma: Radiation for Stage I-II Disease and Evolving Role

## Introduction

Seminoma is highly radiosensitive, which historically made radiation therapy a cornerstone of treatment. However, over the past twenty years, the role of radiation has shifted considerably due to concerns about late effects, particularly the risk of secondary malignancies and cardiovascular disease in this young patient population, who generally have excellent long-term survival. As a result, active surveillance has become the preferred approach for stage I disease, and chemotherapy is increasingly used for stage II disease. Nonetheless, radiation therapy remains a valid and effective option in selected clinical scenarios.

## Staging and Workup

Clinical staging of seminoma is based on the extent of disease spread. Stage I indicates the tumor is confined to the testis without any nodal or distant metastases. Stage IIA involves retroperitoneal lymph node metastases with the largest node measuring 2 cm or less. Stage IIB includes retroperitoneal nodes between 2 and 5 cm, while stage IIC is characterized by nodes larger than 5 cm.

The essential workup for seminoma includes serum tumor markers such as beta-human chorionic gonadotropin (beta-hCG), alpha-fetoprotein (AFP), which must be normal in pure seminoma, and lactate dehydrogenase (LDH). Imaging with computed tomography (CT) of the chest, abdomen, and pelvis is necessary for staging. Radical inguinal orchiectomy serves both diagnostic and therapeutic purposes. Positron emission tomography/computed tomography (PET/CT) may be considered for evaluating residual masses after treatment, as seminoma is typically PET-avid.

## Stage I Seminoma

Management options for stage I seminoma include active surveillance, adjuvant radiation therapy, and single-agent carboplatin chemotherapy. Active surveillance is preferred by most guidelines due to its excellent outcomes. The relapse rate under surveillance is approximately 15-20% at five years, with most relapses occurring within the first two years. Importantly, salvage treatment upon relapse is highly effective, resulting in disease-specific survival rates approaching 99%. This strategy requires reliable patient adherence to follow-up imaging protocols.

When adjuvant radiation is chosen, the target is limited to the para-aortic lymph nodes on the same side as the primary tumor. The standard dose is 20 Gy delivered in 10 fractions, a regimen established by the Medical Research Council (MRC) TE18 trial, which demonstrated equivalence to the previously used 30 Gy dose but with reduced acute toxicity. The radiation field is a para-aortic strip extending from vertebral levels T11 to L5. The older hockey-stick or dog-leg field, which included the ipsilateral iliac nodes, has been abandoned due to increased toxicity. With adjuvant radiation, the relapse rate drops to less than 3-4% at five years.

The MRC TE18 trial compared 20 Gy versus 30 Gy for adjuvant radiation in stage I seminoma and found that 20 Gy was non-inferior in terms of relapse-free survival, with the added benefit of reduced acute side effects. This trial established 20 Gy as the standard dose when radiation is employed.

An alternative to radiation is adjuvant carboplatin chemotherapy, typically administered as a single cycle with an area under the curve (AUC) of 7. The MRC TE19 trial showed that carboplatin provides relapse-free survival equivalent to para-aortic radiation. Carboplatin offers the convenience of a single-day treatment and avoids radiation exposure.

![Para-aortic radiation field for stage I seminoma](images/seminoma-para-aortic-field.jpg)

## Stage II Seminoma

For stage IIA seminoma, radiation therapy involves delivering 30 Gy to the para-aortic and ipsilateral iliac lymph nodes using a dog-leg field, with an additional 6 Gy boost to the involved nodes, totaling 36 Gy to gross disease. This approach achieves relapse-free survival rates of 90-95%. Chemotherapy, consisting of three cycles of bleomycin, etoposide, and cisplatin (BEP) or four cycles of etoposide and cisplatin (EP), is an alternative treatment option.

In stage IIB disease, radiation therapy is similar, with 30 Gy to the dog-leg field and a boost to 36 Gy for gross disease, resulting in relapse-free survival of 85-90%. However, chemotherapy is increasingly preferred in this setting due to lower relapse rates and the avoidance of late radiation-related toxicities. The National Comprehensive Cancer Network (NCCN) guidelines list both radiation and chemotherapy as category 1 options for stage IIB seminoma.

| Stage | Preferred Management | RT Dose (if used) | RT Field | Relapse-Free Survival |
|---|---|---|---|---|
| I | Active surveillance (preferred) | — | — | ~99% DSS with salvage |
| I (adjuvant RT) | Para-aortic RT | 20 Gy / 10 fx | Para-aortic strip (T11–L5) | 96–97% |
| I (adjuvant chemo) | Carboplatin AUC 7 x 1 | — | — | ~96% |
| IIA | RT or chemotherapy | 30 Gy + 6 Gy boost (36 Gy total) | Dog-leg (PA + ipsilateral iliac) | 90–95% |
| IIB | RT or chemotherapy (chemo increasingly preferred) | 30 Gy + 6 Gy boost (36 Gy total) | Dog-leg | 85–90% |
| IIC | Chemotherapy (BEP x 3 or EP x 4) | Not recommended | — | — |

For stage IIC, chemotherapy is the standard of care, typically with three cycles of BEP or four cycles of EP. Radiation is generally not used in stage IIC because the large radiation fields required are associated with inferior outcomes and increased toxicity.

The radiation technique for stage II seminoma involves the dog-leg field, which includes the ipsilateral para-aortic and iliac lymph nodes. The superior border is at the T10-T11 vertebral level, and the inferior border extends to the obturator foramen. Efforts should be made to shield the contralateral kidney when possible. Intensity-modulated radiation therapy (IMRT) or three-dimensional conformal radiation therapy (3D-CRT) techniques are typically employed.

![Dog-leg radiation field for stage IIA-IIB seminoma](images/seminoma-dogleg-field.jpg)

## Late Effects and the Declining Role of RT

Radiation therapy to infradiaphragmatic fields increases the risk of secondary solid tumors within the radiation field, including cancers of the stomach, pancreas, and bladder. This elevated risk persists for decades after treatment, with a relative risk approximately 1.5 to 2 times higher compared to orchiectomy alone.

Radiation to the para-aortic and pelvic regions may also increase long-term cardiovascular risk, although the evidence base is suboptimal. Nonetheless, concerns about cardiovascular disease have contributed to changes in clinical practice.

Regarding fertility, scatter radiation dose to the remaining testis can impair spermatogenesis. Testicular shielding is therefore recommended during radiation delivery. Most patients recover spermatogenesis within one to two years following treatment.

Given the excellent salvage rates with surveillance and the potential for late toxicities from radiation, active surveillance has become the dominant strategy for stage I seminoma. For stage IIA and IIB disease, chemotherapy is increasingly favored, especially for stage IIB. Radiation remains appropriate for patients who prefer a definitive local treatment or have contraindications to chemotherapy.

![Long-term secondary malignancy risk after infradiaphragmatic radiation for seminoma](images/seminoma-secondary-cancer-risk.jpg)

## Key Clinical Pearls

Active surveillance is the preferred management strategy for stage I seminoma, with relapse-free survival approaching 99% when salvage therapy is included. When radiation is utilized for stage I disease, the standard dose is 20 Gy in 10 fractions directed to the para-aortic strip, as established by the MRC TE18 trial. For stage IIA and IIB seminoma, radiation to the dog-leg field with 30 Gy plus a boost to 36 Gy achieves relapse-free survival rates between 85 and 95%, but chemotherapy is increasingly favored due to concerns about late toxicity. The primary reason for the declining role of radiation in seminoma management is the risk of late effects, including secondary malignancies and cardiovascular disease.

## References

1. Fossa SD, Horwich A, Russell JM, et al. Optimal planning target volume for stage I testicular seminoma: a Medical Research Council randomized trial. *J Clin Oncol*. 1999;17(4):1146-1154.  
2. Jones WG, Fossa SD, Mead GM, et al. Randomized trial of 30 versus 20 Gy in the adjuvant treatment of stage I testicular seminoma (MRC TE18). *J Clin Oncol*. 2005;23(6):1200-1208.  
3. Oliver RT, Mead GM, Rustin GJ, et al. Randomized trial of carboplatin versus radiotherapy for stage I seminoma: mature results on relapse and contralateral testis cancer rates (MRC TE19/EORTC 30982). *J Clin Oncol*. 2011;29(8):957-962.  
4. NCCN Clinical Practice Guidelines in Oncology: Testicular Cancer. Version 1.2025.