Clinicopathologic Features and Survival Outcomes of Secondary Mantle Cell Lymphoma after Primary Solid Malignancy
Authors: Shameem Raji , Hamid Muhammad Saad , Hossain Nasheed Mohammad , Mufson Jeffrey , Kropf Patricia L. 
Published: October 2019

Abstract
Background: Mantle Cell Lymphoma (MCL) is a rare sub-type of Non-Hodgkin's Lymphoma (NHL). Outcomes of secondary MCL (sMCL) in patients with a prior diagnosis of a solid malignancy as compared to de novo MCL are not well understood. Differences may be attributable to age, gender, race/ethnicity, extra-nodal involvement, and stage at initial diagnosis. We sought to determine differences in outcome by analyzing data from a large nationwide cancer registry.
Methods: The Surveillance Epidemiology and End Results (SEER) database (1973-2012) was used to detect MCL (ICD-O-3 code: 9673/3) adult (>18 years) cases. The variable "First Malignant Primary Indicator" was used to differentiate between de novo and sMCL cases. Primary solid malignancy subtypes categorized included prostate, breast, colorectal, lung bladder, renal, head and neck, thyroid, testicular, and endometrial cancer. Selected sMCL cases included patients with a diagnosis of a primary solid malignancy with a latency period ≥ 2 months. Overall survival (OS) was calculated using the cox regression model to determine the impact of sMCL on survival, adjusting for age at diagnosis, race/ethnicity, primary solid malignancy subtype type and latency period. Chi square test was utilized to ascertain for any significant difference between de novo MCL and sMCL cases.
Results: Overall, 8,889 patients were included: 875 (9.8%) sMCL and 8,014 (90.2%) de novo MCL cases. For de novo MCL, 67.1% were males. Race/ethnicity in descending frequency consisted of Non-Hispanic Whites (NHW) (81.8%), Hispanics (8.4%), Blacks (4.4%), Asian and Pacific Islanders(API)(4.1%) and American Indian/Native Indian (AI) (0.4%). The most frequent stage at initial diagnosis for de novo MCL was stage IV (57.9%) followed by stage III (13.4%), stage II (8.1%) and stage I (10.0%). Males consisted of 75.4% of sMCL cases. Cases of sMCL categorized by race/ethnicity in descending frequency were NHW (87.3%), Hispanics (5.1%), Blacks (4.2%), API (3.2%) and AI (0.1%). Stage at diagnosis for sMCL was most frequently stage IV (54.6%), followed by stage III (15.8%), stage II (10.9%) and stage I (11.7%). Compared to de novo MCL, sMCL cases were more likely to occur in patient's ≥75 years (48.3% vs. 28.7%, p<0.01). An absence of extra-nodal involvement at diagnosis was common in both de novo MCL (84.0%) and sMCL (83.7%). Specific to sMCL cases, more than 90% of primary solid malignancies were limited to local/regional involvement. All primary solid malignancy subtypes except for head and neck (48 months) and renal cancer (59 months) had a latency period of greater 5 years. Median OS was significantly worse in sMCL (34 months) compared to de novo MCL (53 months) (HR: 1.375, 95% CI:1.243-1.504).
Conclusion: Our analysis demonstrates that elderly age appears to be significantly more common in sMCL cases as compared to de novo MCL. By contrast, race/ethnicity, and extra-nodal involvement were similar between the two groups. Survival was worse in sMCL compared to de novo MCL. This may be due to differences in treatment preferences. Further studies are necessary to elucidate the etiology for such differences in outcomes.

Disclosures
Kropf: Teva Pharmaceuticals: Consultancy.