Background The immune system plays an important role in cancer surveillance and therapy. Chemoradiation can cause severe treatment-related lymphopenia (TRL) (<500 cells/mm3) that is associated with reduced survival. Materials and Methods Data from 4 independent solid tumor studies on serial lymphocyte counts, prognostic factors, treatment, and survival were collected and analyzed. The data set included 297 patients with newly diagnosed malignant glioma (N=96), resected pancreatic cancer (N=53), unresectable pancreatic cancer (N=101), and non–small cell lung cancer (N=47). Results Pretreatment lymphocyte counts were normal in 83% of the patient population, and no patient had severe baseline lymphopenia. Two months after initiating chemoradiation, 43% developed severe and persistent lymphopenia (P=.001). An increased risk for death was attributable to TRL in each cancer cohort (gliomas: hazard rate [HR], 1.8; 95% CI, 1.13–2.87; resected pancreas: HR, 2.2; 95% CI, 1.17–4.12; unresected pancreas: HR, 2.9; 95% CI, 1.53–5.42; and lung: HR, 1.7; 95% CI, 0.8–3.61) and in the entire study population regardless of pathologic findings (HR, 2.1; 95% CI, 1.54–2.78; P<.0001). Severe TRL was observed in more than 40% of patients 2 months after initiating chemoradiation, regardless of histology or chemotherapy regimen, and was independently associated with shorter survival from tumor progression. Conclusions Increased attention and research should be focused on the cause, prevention, and reversal of this unintended consequence of cancer treatment that seems to be related to survival in patients with solid tumors.

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Objectives Lymphopenia is a common consequence of chemoradiation therapy yet is seldom addressed clinically. This study was conducted to determine if patients with locally advanced pancreatic cancer (LAPC) treated with definitive chemoradiation develop significant lymphopenia and if this affects clinical outcomes. Methods A retrospective analysis of patients with LAPC treated with chemoradiation at a single institution from 1997 to 2011 was performed. Total lymphocyte counts (TLCs) were recorded at baseline and then monthly during and after chemoradiation. The correlation between treatment-induced lymphopenia, established prognostic factors, and overall survival was analyzed using univariate Cox regression analysis. Important factors identified by univariate analysis were selected as covariates to construct a multivariate proportional hazards model for survival. Results A total of 101 patients met eligibility criteria. TLCs were normal in 86% before chemoradiation. The mean reduction in TLC per patient was 50.6% (SD, 40.6%) 2 months after starting chemoradiation (P< 0.00001), and 46% had TLC< 500 cells/mm3. Patients with TLC < 500 cells/mm3 2 months after starting chemoradiation had inferior median survival (8.7 vs. 13.3mo, P= 0.03) and PFS (4.9 vs. 9.0mo, P = 0.15). Multivariate analysis revealed TLC< 500 cells/mm3 to be an independent predictor of inferior survival (HR= 2.879, P= 0.001) along with baseline serum albumin (HR= 3.584, P = 0.0002), BUN (HR = 1.060, P= 0.02), platelet count (HR= 1.004, P = 0.005), and radiation planning target volume (HR= 1.003, P= 0.0006). Conclusions Severe treatment-related lymphopenia occurs frequently after chemoradiation for LAPC and is an independent predictor of inferior survival.

Purpose Radiation-induced lymphopenia (RIL) is associated with inferior survival in patients with glioblastoma, lung cancer, and pancreatic cancer. We asked whether stereotactic body radiation therapy (SBRT) decreases severity of RIL compared to conventional chemoradiation therapy (CRT) in locally advanced pancreatic cancer (LAPC). Methods and Materials Serial total lymphocyte counts (TLCs) from patients enrolled in a prospective trial of SBRT for LAPC were compared to TLCs from an existing database of LAPC patients undergoing definitive CRT. SBRT patients received 33 Gy (6.6 × Gy 5 fractions). CRT patients received a median dose of 50.4 Gy (1.8 Gy × 28 fractions) with concurrent 5-fluorouracil (77%) or gemcitabine (23%) therapy. Univariate and multivariate analyses (MVA) were used to identify associations between clinical factors and post-treatment TLC and between TLC and survival. Results Thirty-two patients received SBRT and 101 received CRT. Median planning target volume (PTV) was smaller in SBRT (88.7 cm3) than in CRT (344.6 cm3; P<.001); median tumor diameter was larger for SBRT (4.6 cm) than for CRT (3.6 cm; P=.01). SBRT and CRT groups had similar median baseline TLCs. One month after starting radiation, 71.7% of CRT patients had severe lymphopenia (ie, TLC <500 cells/mm3 vs 13.8% of SBRT patients; P<.001). At 2 months, 46.0% of CRT patients remained severely lymphopenic compared with 13.6% of SBRT patients (P=.007). MVA demonstrated that treatment technique and baseline TLCs were significantly associated with post-treatment TLC at 1 but not 2 months after treatment. Higher post-treatment TLC was associated with improved survival regardless of treatment technique (hazard ratio [HR] for death: 2.059; 95% confidence interval: 1.310–3.237; P=.002). Conclusions SBRT is associated with significantly less severe RIL than CRT at 1 month in LAPC, suggesting that radiation technique affects RIL and supporting previous modeling studies. Given the association of severe RIL with survival in LAPC, further study of the effect of radiation technique on immune status is warranted.