Association of Dosimetric and Treatment Related Factors with Radiation Induced Lymphopenia and Overall Survival among Patients Treated in the FOLFIRINOX Era

Abstract

To determine whether radiation to the spleen with concurrent chemotherapy is associated with lymphopenia and ultimately worse survival outcomes in patients with locally advanced pancreatic cancer. Retrospective review of 92 pancreatic cancer patients treated at Massachusetts General Hospital with neoadjuvant FOLFIRINOX for 8 cycles followed by consolidative pre-operative RT (median dose 50.4 Gy) with concurrent capecitabine and surgical resection (39%) from 2010-2016. Absolute lymphocyte count (ALC) was recorded at baseline, post-chemotherapy and post-RT. Basic clinical and demographic variables were collected for all patients. DVH parameters were collected for both spleen and liver. Median ALC was similar before and after neoadjuvant chemotherapy (1.4 vs. 1.3; p=0.23), but declined significantly after chemo-RT (1.4 vs. 0.6, p<0.001). Median hemoglobin (HgB, 12.9 vs. 11.6, p<0.001) and platelets (223.5 vs. 156.0, p<0.001) also significantly declined after chemo-RT. On multivariable logistic regression, higher risk of post-RT grade IV lymphopenia was associated with lower baseline ALC count (p=0.001), female gender (p=0.001), no surgical resection (p=0.03), and larger spleen volume (p=0.003). On multivariable Cox regression, at a median follow-up of 13.5 months, improved overall survival was associated with having a surgical resection (p=0.001), younger age (p=0.02), and lower spleen V5 (p=0.003), but not gender, pre/post-RT ALC or any other spleen/liver DVH parameters. Chemo-RT for pancreatic cancer is associated with a significant decline in ALC. Gender, baseline ALC and spleen volume predict for post-treatment ALC. In our series, in the setting of FOLFIRINOX and improved rates of resection, ALC was not associated with overall survival.Abstract SU_19_2182; Table 1Change in blood count over the course of treatmentBaselinePost-ChemoPost-RTBaseline vs. Post ChemoPost-Chemo vs. Post-RTBaseline vs. Post-RTLymphopenia<Grade III71 (77%)68 (74%)22 (24%)P=0.72P<0.001P<0.001Grade III18 (20%)22 (24%)38 (41%)Grade IV3 (3%)2 (2%)32 (35%)ANC, median (IQR)4.3 (3.2, 6.2)4.2 (3.0, 5.9)2.9 (2.3, 3.9)P=0.29P<0.001P<0.001ALC, median (IQR)1.4 (1.0, 2.0)1.3 (1.0, 1.6)0.6 (0.4, 0.9)P=0.23P<0.001P<0.001ANC/ALC ratio, median (IQR)3.1 (2.0, 5.3)3.2 (2.2, 5.1)5.2 (3.4, 8.6)P=0.80P<0001P<0.001WBC, median (IQR)6.8 (5.2, 9.0)6.5 (4.9, 8.6)4.5 (3.5, 5.3)P=0.23P<0.001P<0.001HgB, median (IQR)12.9 (12.1, 13.9)11.3 (10.3, 12.2)11.6 (10.1, 12.8)P<0.001P=0.21P<0.001Platelets, median (IQR)223.5 (169.0, 298.5)172.5 (127.5, 217.5)156 (114.5, 200.0)P<0.001P=0.094P<0.001 Open table in a new tab