Impact of radiotherapy parameters on the risk of lymphopenia in urological tumors: A systematic review of the literature.

Background: We investigated how radiotherapy (RT) parameters may contribute to the risk of lymphopenia in urological tumors and we discussed how this may impact clinical outcomes.

Material & Methods: A systematic review was performed according to the preferred reporting items for systematic reviews and meta-analysis (PRISMA) guidelines. The PubMed, Embase and ISI Web Of Knowledge databases were searched. Study quality was assessed according to the Newcastle-Ottawa Scale.

Results: Overall, 8 articles reporting on a total of 549 urological cancer patients met the inclusion criteria. The pooled mean incidence of acute severe lymphopenia (absolute lymphocyte count < 500 cells/µL) was 17.1%. Extended radiation volumes may lead to an increased risk of developing lymphopenia. Medium-high doses (≥ 40 Gy) to the whole pelvic (odds ratio (OR) = 1.01; 95% confidence interval (CI) 1.00-1.01; p = 0.025) and iliac (OR = 1.04; 95% CI 1.01-1.08; p = 0.009) bone marrow (BM) were associated with acute grade 3 and late grade 2 lymphopenia, respectively.

Conclusion: Multiple studies reported high and severe incidences of lymphopenia. Minimizing radiation volumes and unintentional irradiation of pelvic BM may reduce the incidence of lymphopenia, potentially improving clinical outcomes. More research is needed to further elucidate these findings and effectively implement recently developed new risk assessment tools.