Multiple myeloma in association with second malignancy.

Purpose: To look at the frequency of second primary malignancies (SECMAL) in patients with multiple myeloma (MM).

Methods: The medical files of 332 patients with MM (whole group), diagnosed and treated at the University Multiprofile Hospital for Active Treatment "Sv. Georgi" and the Comprehensive Oncology Hospital (Plovdiv) for a 20-year period (1990-2010) were retrospectively analyzed. MM patients with SECMAL constituted the study group. A control group comprised patients with solid tumors associated with SECMAL. This group derived from a sample of 21768 patients with solid tumors.

Results: In the study group, SECMAL was diagnosed in 4.52% (N=15) of the patients, while in the control group this figure was 5.09% (N=1108) (p>0.05). The diagnosis of MM preceded the occurrence of SECMAL in 35.71% of the study group patients, the median interval being 6.6 years (range 5-14). More frequently the diagnosis of the solid tumor preceded the occurrence of MM (66.67%). Breast cancer and gastric cancer were encountered with the highest frequency (26.67% each). The median survival (77.2 months, range 44-129) was significantly longer in the group with MM and SECMAL compared to the whole group with MM (median 38.6 months, range 10-58; p<0.05).

Conclusion: The rate of MM with other malignant diseases is comparable with the frequency of SECMAL in other lymphoproliferative disorders and solid tumors. The occurrence of SECMAL during the clinical course of MM is not a frequent event and is expected in the rare cases with longer survival.