Background
Retrospective analysis from St. Jude Children's Research Hospital. Children with ALL who experienced testicular relapse. Evaluated outcomes of testicular irradiation (20–24 Gy) combined with systemic re-induction chemotherapy for isolated testicular relapse vs overt bilateral testicular disease. Aimed to define RT dose adequacy and long-term testicular function outcomes.
Interventions and follow up
Arm A: Bilateral testicular irradiation 20–24 Gy (1.5–2.0 Gy/fx) + re-induction chemotherapy for isolated testicular relapse
Primary endpoint: Testicular relapse rate, overall re-relapse rate, testicular functio
mFollow up: 5.0 year
Primary endpoint: Testicular relapse rate, overall re-relapse rate, testicular functio
mFollow up: 5.0 year
Results
Arm B (comparison): Unilateral RT (ipsilateral overt + contralateral prophylactic) — historical comparison
Testicular re-relapse rate (RT + chemo): <5% — excellent local control
5-yr OS after testicular relapse: ~70% (isolated late testicular relapse) vs ~40% (early testicular relapse)
Testicular hormone function: Testosterone production preserved in most; azoospermia nearly universal after 20–24 Gy
Testicular re-relapse rate (RT + chemo): <5% — excellent local control
5-yr OS after testicular relapse: ~70% (isolated late testicular relapse) vs ~40% (early testicular relapse)
Testicular hormone function: Testosterone production preserved in most; azoospermia nearly universal after 20–24 Gy
Adverse events
Main adverse events: Azoospermia/infertility: near-universal after bilateral 20–24 Gy. Testosterone production: generally maintained (Leydig cells more radio-resistant than spermatogonia). Growth/pubertal development: preserved if RT given after puberty. Scrotal skin reaction: mild with modern fractionation.
Conclusions
Bilateral testicular RT 20–24 Gy with re-induction chemotherapy achieves excellent local control for isolated testicular ALL relapse. Late isolated testicular relapse (off therapy) has favorable outcome with re-treatment. Azoospermia is essentially universal, making sperm banking before treatment essential when feasible in pubertal patients.
Key Limitations
Key Limitations: Retrospective, single-institution. Small sample size. Definition of "isolated" testicular relapse requires careful bone marrow and CNS staging. Molecular monitoring (MRD) not available in this era to detect subclinical systemic disease. Modern surveillance ultrasound may identify relapse earlier.
Clinical Context
Bilateral testicular RT 24 Gy remains standard for overt testicular relapse in ALL. Intensity of systemic therapy depends on timing (early vs late relapse) and MRD response. Sperm cryopreservation should be offered to all pubertal males before testicular RT. Testosterone monitoring at puberty is standard follow-up.
References