A Systematic Review of Radiation-Related Lymphopenia in Genito-urinary Malignancies

The impact of radiation-related lymphopenia on clinical outcomes has been reported in various solid malignancies such as high grade gliomas, head and neck cancers, thoracic malignancies and gastro-intestinal malignancies but its impact is not clearly known in the context of common genito-urinary (GU) malignancies.

To better understand the effect of radiation-associated lymphopenia in prostate and bladder cancer, we undertook this systematic review of clinical studies that have studied radiation-related lymphopenia in GU malignancies. A systematic methodology search of PubMed, Embase, and Cochrane library resulted in 2125 abstracts. Ten studies fulfilled the inclusion criteria which included any prospective, retrospective study or cohort study of prostate, urinary bladder, kidney, ureter, urethra, penile cancer in humans, and radiation should be part of treatment and intent has to be in definitive or adjuvant settings. Finally the study should have data on radiation-related lymphopenia.

Four studies reported on the cancer-specific outcomes related to the lymphopenia. The incidence of low lymphocyte counts were documented in all the studies. Three studies analyzed the factors associated with the Lymphocyte depletion. Pooled incidence of severe lymphopenia was 29.25% and mild to moderate lymphopenia was 60.75%. Bone marrow volume receiving 40 Gy was associated with the incidence of lymphopenia.

One-third of the patients suffer from severe lymphopenia after radiation in prostate and bladder cancer. There are no clear data to support the correlation between severe lymphopenia and disease outcomes. Bone marrow dosimetry can affect the incidence and severity of lymphopenia. There is need of prospective datasets to identify the impact of radiation-related lymphopenia in GU malignancies focusing on long-term side effects, recurrence rates, and overall survival.