Significance of c-myc Rearrangements in Diffuse Large B-Cell Lymphoma.

Abstract Rearrangements of the c-myc oncogene can be seen in 5–10% of patients with diffuse large B-cell lymphoma. However, studies examining the significance of this finding have yielded conflicting results. Therefore, we performed a retrospective analysis to determine the clinical significance of c-myc rearrangements in diffuse large B-cell lymphoma. The results of classical cytogenetic studies and FISH analyses were used to identify diffuse large B-cell lymphoma cases in the database of the Nebraska Lymphoma Study Group with or without c-myc rearrangements. Patients who were HIV positive and those with post-transplant lymphoproliferative disease were excluded. We identified 16 patients with diffuse large B-cell lymphoma and c-myc rearrangements. All patients were initially treated with doxorubicin- or mitoxantrone-containing chemotherapy regimens. The median age of these 16 patients was 61 years (range 40 to 80), and 5 (31%) were males. The International Prognostic Index (IPI) was 0–2 at diagnosis in 9 patients (56%), and 3–5 in 7 patients (44%). Eleven patients (69%) had bulky disease (≥ 5 cm) at diagnosis. No significant differences in outcome were identified when the 16 c-myc positive patients were compared with 97 c-myc negative diffuse large B-cell lymphoma patients in the same age range. The actuarial 5-year progression-free survival for the c-myc positive patients was 23% (95% CI 6% to 46%), as compared with 38% (95% CI 29% to 48%) for c-myc negative patients (p=0.17). The actuarial 5-year overall survival rates were 36% (95% CI 14% to 59%) and 47% (95% CI 36% to 56%), respectively (p=0.19). Classical cytogenetics and FISH analyses were also used to examine the 16 c-myc positive cases for bcl-2 rearrangements. Eight (50%) cases had rearrangements of bcl-2 in addition to c-myc rearrangements. These patients were similar to the c-myc positive/bcl-2 negative patients except for a higher likelihood of an elevated LDH level at diagnosis (88% vs. 25%; p=0.03). The actuarial 5-year progression-free survival for c-myc positive/bcl-2 positive patients was 0%, as compared to 33% (95% CI 6% to 66%) for patients with rearrangements of c-myc alone, and 37% (95% CI 28% to 47%) for c-myc negative patients. The actuarial 5-year overall survival rates were 12% (95% CI 1% to 42%), 47% (95% CI 12% to 76%), and 41% (95% CI 31% to 51%), respectively. A multivariate analysis, adjusting for IPI score, demonstrated that the relative risk (RR) of treatment failure was significantly worse for the c-myc positive/bcl-2 positive patients, as compared to the c-myc negative patients (RR 2.86, 95% CI 1.32–6.23; p=0.008). Similarly, mortality was also significantly worse for the c-myc positive/bcl-2 positive patients, as compared to the c-myc negative patients (RR 2.69, 95% CI 1.18–6.11; p=0.02). In contrast, no significant differences in treatment failure or overall survival were demonstrated when c-myc positive/bcl-2 negative patients were compared with c-myc negative patients. Our results demonstrate that the c-myc rearrangement is not associated with poorer survival in patients with diffuse large B-cell lymphoma. However, patients with rearrangements of bcl-2 in addition to c-myc had significantly worse progression-free survival and overall survival.