An Institutional Experience: Correlation Between Absolute Lymphocyte Count and Survival Outcome After Reduced Intensity Conditioning Allogeneic Stem Cell Transplant in Patients with Hematologic Malignancies

Allogeneic stem cell transplant (SCT) is currently the standard of care in the consolidative treatment of several hematologic malignancies. Typically after a stem cell transplant the monocytes engraft first, followed by the granulocytes, macrophages and then natural killer cells. Lymphocyte recovery is considered to be an indicator of immune reconstitution during SCT and correlation between rate of recovery of lymphocyte count and patient outcome has been reported in patients after a myeloablative allogeneic transplant. Studies suggest that early lymphocyte recovery may be a predictive marker of engraftment and survival post-myeloablative SCT. However, there is minimal data on lymphocyte recovery after reduced intensity conditioning allogeneic SCT. We report our institutional experience on the correlation between rate of absolute lymphocyte recovery and survival in patients with a hematological malignancy after a reduced intensity conditioning allogeneic SCT.

We performed a retrospective review of all adult patients who underwent reduced intensity conditioning chemotherapy followed by an allogeneic SCT at the Robert H. Lurie Comprehensive Cancer Center of Northwestern University from March 2001 to March 2008. We looked at the post- allograft absolute lymphocyte count (ALC) at 3 different time points – day 15, 21 and 28. Patients were then analyzed based on ALC cutoff values of 200/mm³, 500/mm³ and 1000/mm³. For each of the cutoff values, patients were divided into 2 groups: those with absolute lymphocyte count of less than or equal to the cutoff value and those with ALC of greater than the cutoff value.

A total of 131 consecutive patients were included in the analysis; 46.6% were male and 53.4% were female. 51.1% patients underwent matched sibling (MSD) while 48.9% had matched unrelated donor (MUD) SCT. Overall survival was determined in 117 patients; 14 patients were excluded due to incomplete data. At day 15 and 28, patients with an ALC of greater 200/mm³ had a statistically significant overall survival compared to those that were less than 200/mm³, p= 0.016 and p=0.05, respectively. An ALC of greater than 1000/mm³ at day 15 seemed to predict for a worse outcome compared to those with an ALC of less than 1000/mm³ (p=0.008). There were however six times more people in the group with ALC less than 1000/mm³ at day 15, compared to those with ALC greater than 1000/mm³. An ALC of greater than or less than 500/mm³did not significantly appear to affect overall survival at any of the time points evaluated.

ALC of greater than 200/mm³ at day 15 and 28 in our patient population appears to be predictive of overall survival after a reduced intensity conditioning stem cell transplant in patients with a hematological malignancy. However, the relationship between ALC and outcome is inconsistent and needs to be explored further in the context of other prognostic factors.

No relevant conflicts of interest to declare.