Background
Phase III RCT (MRC TE18/EORTC 30942). 625 patients with stage I seminoma after orchidectomy randomized to adjuvant radiotherapy targeting either the para-aortic (PA) field alone vs the traditional dog-leg (DL) field (para-aortic + ipsilateral iliac). Designed to determine whether reducing RT field size maintained efficacy while reducing toxicity. Median follow-up 4.5 years.
Interventions and follow up
Arm A: Para-aortic (PA) radiotherapy 30 Gy in 15 fractions to T10–L5 para-aortic nodes only (n=313)
Arm B: Dog-leg (DL) radiotherapy 30 Gy in 15 fractions to para-aortic + ipsilateral pelvic nodes (n=312)
Primary endpoint: Relapse-free survival (non-inferiority)
mFollow up: 4.5 year
Arm B: Dog-leg (DL) radiotherapy 30 Gy in 15 fractions to para-aortic + ipsilateral pelvic nodes (n=312)
Primary endpoint: Relapse-free survival (non-inferiority)
mFollow up: 4.5 year
Results
Relapse-free survival at 3 years: 96.0% (PA) vs 96.6% (DL) — non-inferiority of PA field confirmed
Pelvic relapse rate: 2% (PA arm) — acceptable given pelvic lymph node involvement rare in stage I seminoma without vascular invasion
Acute GI toxicity: Significantly less in PA arm (P<.001)
Subfertility (azoospermia/oligospermia): Significantly less in PA arm
Pelvic relapse rate: 2% (PA arm) — acceptable given pelvic lymph node involvement rare in stage I seminoma without vascular invasion
Acute GI toxicity: Significantly less in PA arm (P<.001)
Subfertility (azoospermia/oligospermia): Significantly less in PA arm
Adverse events
Main adverse events: PA field RT associated with significantly less acute nausea, diarrhea, and lethargy. Lower incidence of temporary subfertility. No difference in late toxicity or second malignancy rates at this follow-up.
Conclusions
Para-aortic field radiotherapy is non-inferior to dog-leg irradiation for stage I seminoma and is associated with less acute GI toxicity and better preservation of fertility. PA-only field RT became the standard adjuvant approach for stage I seminoma following this trial.
Key Limitations
Key Limitations: Median follow-up 4.5 years — long-term relapse and second malignancy data are not captured. The ~2% pelvic relapse rate with PA-only field requires careful patient selection (absence of T3 or scrotal violation). Carboplatin-based chemotherapy and active surveillance have since become common alternatives to RT for stage I seminoma, and this trial does not address those comparisons.
Clinical Context
MRC TE18/EORTC 30942 established PA-only field as the preferred RT technique for stage I seminoma adjuvant treatment. However, contemporary practice has largely shifted toward carboplatin (1–2 cycles) or active surveillance due to concerns about long-term second malignancy risk from RT, reducing the clinical application of this trial's findings.
References
References: Jones WG et al, JCO 2005 (MRC TE18/EORTC 30942)