PURPOSE: 454 patients with prostate adenocarcinoma were accidentally overexposed 
to radiation in Epinal hospital, France, between August 1999 and January 2007. 
We aimed toevaluate whether radiation-induced CD4 or CD8 T-lymphocyte apoptosis 
(RILA) correlates with the severity of radiation toxicity.
METHODS: Between 2007 and 2013, all patients who received more than 108% of the 
prescribed radiation dose, after correction of the treatment plan, were 
convened, and blood was sampled at 6-months follow-up. Maximal Digestive 
toxicity (MDT) and maximal urinary toxicity (MUT) were graded using the Common 
Terminology Criteria for Adverse Events (NCI-CTCAE) v3.0 scale. RILA was 
assessed using flow cytometry.
RESULTS: 245 patients were included in our study. After a median follow-up of 
4.8 years, the MDT and MUT reached grade 3-4 in 37 patients and 56 patients, 
respectively. Patients with prostatectomy exhibited a statistically higher grade 
of MUT compared with those treated with definitive radiotherapy (p=0.03). The 
median RILA values were 11.8% and 15.3% for CD4 and CD8 T-lymphocytes, 
respectively. We found no significant correlation between CD4 or CD8 RILA and 
either MDT or MUT.
CONCLUSION: RILA does not correlate with the inter-individual variation in MDT 
or MUT in the largest cohort of patients overexposed to radiation. The magnitude 
of the overdosage probably overrides biological predictors of toxicity, 
including individual radiosensitivity.