Confirming the Presence of a Smoldering T and B PLL Associated with Improved 5 Year OS: Using the National Cancer Data Base

Background:

Prolymphocytic leukemia (PLL) is a rare cancer with incidence of 0.48/1,000,000. It is comprised of 2 subtypes, T or B cell. It generally is associated with a poor median OS of 1-3 years. However, some patients have an initial smoldering course not requiring treatment. Limited population data exists describing the outcomes of PLL. We studied PLL patients who met a definition of smoldering, not requiring treatment within 180 days of diagnosis, using the National Cancer Data Base (NCDB).

Methods:

Patient level data were obtained from the NCDB Participant User File. The NCDB collects hospital cancer registry data representing 70% of newly diagnosed cancer cases in the US population. We identified PLL patients (ICD-O: 9832 PLL, NOS, ICD-O: 9833 B-PLL, and ICD-O: 9834 T-PLL) diagnosed in 2004-2015 for demographics, disease and treatment characteristics. We included patients diagnosed from 2004-2013 in the overall survival (OS) analyses. Patients who received no treatment as part of their first course of treatment and who did not have a subsequent treatment within 180 days were considered smoldering PLL.

Results:

From 2004-2015, 1606 patients were diagnosed with PLL and 451(28%) were smoldering PLL. Of the 1606 patients, T-PLL represented 781(49%), B-PLL 480(30%), and PLL, NOS 345(21%). Of the 451 smoldering PLL patients observed as T-PLL represented 48%(215), B-PLL 29%(133), and PLL, NOS 23%(103). The median age at diagnosis was 69 [59 - 78] years. There was a male predominance with 60 % males. The median OS for the entire cohort was 20.6 months. The % 5yr overall survival (OS) for smoldering PLL was 40% vs 29%(for non-smoldering). Within the PLL subtypes PLL, NOS and B-PLL were associated with better 5yr OS 38.56% and 35.53%, compared to T-PLL 12.89%. Only 65(4%) patients underwent an early stem cell transplant(SCT).

Conclusions:

We identified a population of patients not needing treatment within 180 days of diagnosis representing smoldering PLL with a significantly improved OS. Additionally, PLL, NOS and B-PLL were associated with an improved OS. The use of early SCT is low in PLL.