Background
Retrospective single-institution analysis from Germany comparing two dose levels of para-aortic radiotherapy for stage I seminoma. 675 patients treated between 1975 and 2000. Compared standard-dose RT (30 Gy) vs reduced-dose RT (26 Gy) to evaluate whether dose reduction maintained efficacy while reducing toxicity. Median follow-up 7.5 years.
Interventions and follow up
Arm A: Reduced-dose radiotherapy 26 Gy para-aortic field (n=317)
Arm B: Standard-dose radiotherapy 30 Gy para-aortic field (n=358)
Primary endpoint: Relapse-free survival
mFollow up: 7.5 year
Arm B: Standard-dose radiotherapy 30 Gy para-aortic field (n=358)
Primary endpoint: Relapse-free survival
mFollow up: 7.5 year
Results
Relapse-free survival at 5 years (26 Gy): 97.2%
Relapse-free survival at 5 years (30 Gy): 98.3%
Difference: Not statistically significant (P=.38)
Acute GI toxicity: Lower with 26 Gy (P<.05)
Relapse-free survival at 5 years (30 Gy): 98.3%
Difference: Not statistically significant (P=.38)
Acute GI toxicity: Lower with 26 Gy (P<.05)
Adverse events
Main adverse events: Acute GI toxicity (nausea, diarrhea) significantly lower with reduced-dose 26 Gy. No significant difference in late bowel toxicity or second malignancy rates between dose levels at this follow-up.
Conclusions
Reduced-dose 26 Gy para-aortic RT maintains equivalent relapse control compared with 30 Gy for stage I seminoma, with lower acute GI toxicity. These results support dose reduction as safe for stage I seminoma adjuvant RT, providing the basis for the subsequent MRC TE10 trial confirming 20 Gy non-inferiority.
Key Limitations
Key Limitations: Retrospective single-institution design with era-related selection differences. Different RT techniques and fields used over 25 years. Not a randomized comparison. The 26 Gy dose was further reduced to 20 Gy in subsequent trials without significant relapse increase.
Clinical Context
This German series contributed to the dose de-escalation evidence base for stage I seminoma adjuvant RT, ultimately supporting the current standard of 20 Gy in 10 fractions when adjuvant RT is used (as per MRC TE10 and current EAU guidelines). However, adjuvant RT use has declined significantly in favor of surveillance or single-dose carboplatin.
References
References: Classen J et al, JCO 2003