The Recovery of the Absolute Lymphocyte Subpopulation Count in Cervical Cancer Patients after Radiotherapy

Abstract

<h3>Purpose/Objective(s)</h3> Radiotherapy (RT) results in varying degrees of lymphopenia. However, to date, there is still no consensus on the persistence of lymphopenia after RT treatment for cervical cancer. Therefore, this study aimed to evaluate the dynamic changes of absolute lymphocyte subset count (ALSC) in cervical cancer patients after receiving RT. In addition, the study also explored the diagnostic value of the lymphocyte count (LC) in patients with declining ALSC <h3>Materials/Methods</h3> The peripheral blood ALSC was tested by flow cytometry before RT (baseline) and at regular follow-up intervals after completion of RT. The blood cell counts were also collected on the same day. Patient characteristics, tumor variables, and treatment factors were gathered for risk assessment. The primary endpoint was the degree of reduction in the lymphocyte subpopulation and the secondary endpoint was the predictive value of LC for declining ALSC. Logistic regression was used to identify the risk factors of lymphopenia, and the receiver operating characteristic (ROC) curve was used to assess the predictive value of LC. <h3>Results</h3> A total of 260 consecutive cervical cancer patients met the study criteria, among which 228 (87.7%) patients had a reduction in either one or some of the lymphocyte subpopulations. The median percentage decrease in ASLC ranged from 22.52% to 58.32%. When compared with the baseline the lymphocyte subpopulations dropped immediately after initiation of RT, to eventually reach their minimum levels at 3 to 6 months after completion of treatment. The B-lymphocyte and CD4+ to CD8+ ratios recovered within the first 6 months and the CD8+ T cell count recovered to normal levels within one year after completion of RT. In comparison, the CD3+ and CD4+ T cell counts persisted at low levels for one year and recovered five years after RT. The natural killer (NK) cells rarely decreased after RT. Multivariate logistic regression analysis identified advanced tumor stage and age above 60 years as independent risk factors affecting the count of lymphocyte cell subsets after RT. The ROC analysis confirmed that the LC obtained from a routine blood examination could be used to predict the count for each lymphocyte subtype except for the NK cell subtype. <h3>Conclusion</h3> The lymphocyte subpopulation counts decreased immediately after initiation of RT, to eventually reach their minimum levels after 3 to 6 months following completion of treatment, and it took several months or years to recover. Advanced tumor stage and age above 60 were identified as independent risk factors for lymphopenia in cervical cancer patients. The LC was a good predictor of ALSC decline. Therefore, this test could be used as a cheaper alternative to complex ALSC monitoring with flow cytometry.