214 - Impact of Palliative Radiation on Lymphopenia and Survival in Cancer Patients
Presenter(s)
J. J. Kim1, M. Akerman2, W. D. Lindsay3, K. Yee3, J. Herman4,5, and L. Tchelebi6; 1Zucker School of Medicine at Hofstra/Northwell, New Hyde Park, NY, United States, 2Biostatistics Unit, Office of Academic Affairs, New Hyde Park, NY, 3Oncora Medical, Inc, Philadelphia, PA, 4Donald and Barbara Zucker School of Medicine at Hofstra/Northwell, Lake Success, NY, 5Northwell Health Cancer Institute, New Hyde Park, NY, 6Northwell, New Hyde Park, NY
Purpose/Objective(s): Conventionally fractionated radiation therapy (RT) has been shown to induce lymphopenia in cancer patients, which is associated with reduced survival. The impact of shorter courses of lower dose palliative RT on lymphopenia has not been well studied. Herein, we analyze the effect of palliative RT regimens on rates of lymphopenia in a large cohort of cancer patients treated within our health system and its impact on survival.
Materials/Methods: We retrospectively identified all patients within our health system treated with a palliative course of RT in the last 10 years using the data extraction software database. Only patients with information on lymphocyte counts before and after palliative RT were included. Lymphopenia was defined according to Common Terminology Criteria for Adverse Events (CTCAE). Palliative RT was defined as 8 Gray (Gy) in one fraction (Fx), 20 Gy in 5 Fx, or 30 Gy in 10 Fx. A paired t-test was used to compare the absolute lymphocyte counts (ALC) for patients pre- and post- palliative RT. Univariable and multivariable logistic regression was used to determine the effect of palliative RT dose/fractionation on the likelihood of inducing lymphopenia. Results were reported as odds ratios (OR). Kaplan-Meier curves were used to assess the effect of lymphopenia on overall survival (OS), following palliative RT. Groups were compared using the log-rank test, median survival rates were computed. A result was significant at p<0.05.
Results: Out of the 2002 patients who received palliative radiation, 877 had lymphopenia prior to treatment. Of the remaining 1125, 748 developed lymphopenia following palliative RT. There was a significant difference between the pre- and post-treatment ALC values (diff = -0.60; 95% confidence interval for the mean difference: [-0.70, -0.51]), p < 0.001) with a concomitant correlation between receipt of palliative RT and incidence of lymphopenia (37.4% of patients developing lymphopenia. A higher Fx number was associated with increased rates of lymphopenia (24.2% vs. 30.0% vs. 50.6% respectively, p<0.001). In the univariable analyses, subjects who received 5 Fx (OR=1.92; 95% CI: 1.46 - 2.52) or 10 Fx (OR=3.21; 95% CI: 2.27 - 4.53) were approximately 2 and 3 times, respectively, more likely to develop lymphopenia as compared to those who received 1 Fx. After adjusting for age, sex, race, concurrent and prior systemic therapies, and site of radiation, similar results were observed (5 Fx OR=1.86; 10 Fx OR = 3.02). Those who developed lymphopenia following palliative RT had lower median OS compared to those without lymphopenia (17.3 vs. 28.2 months respectively, p<0.01).
Conclusion: Palliative radiation regimens can induce lymphopenia in cancer patients. Increasing number of fractions of palliative RT increases the risk of developing lymphopenia. The presence of lymphopenia following palliative RT is associated with decreased overall survival. Treating physicians should consider dose/fractionation when administering RT in the palliative setting.