Risk of Second Cancers in Waldenstrom Macroglobulinemia: a Population-Based Study From Northern Italy.

An increased incidence of second cancers has been reported in some lymphoproliferative disorders. Whether the predisposition to other malignancies is due to disease-related immune-suppression rather than to the carcinogenic role of therapy given to treat the hematologic disease is still poorly understood.

The aims of this study were to assess the frequency, characteristics and factors predicting second cancers in patients with WM and to evaluate whether WM patients are at increased risk of developing other malignancies as compared to an age- and sex-matched control population.

The clinical records of 220 consecutive WM patients seen in two Hematologic centres of Northern Italy from 1980 to 2008 were reviewed. All cancers, with exception of non-melanoma skin cancers, were considered for this analysis. Standardized incidence ratios (SIRs), defined as the ratio between observed and expected cases, were used to compare the incidence of second cancers in WM with that of the general population. The number of expected cancers was obtained from age, sex and calendar-specific incidence rates reported by AIRTUM (Associazione Italiana Registri Tumori) for Northern Italy. A multivariate Cox proportional hazards regression model was used to examine risk factors for the development of second cancers. Therapy was analyzed as a time-dependent covariate.

The median age of patients was 61 years (range: 26-86), 131 (60%) were males and 89 females (40%). The median follow-up was 4.8 years (range: 0.5-25). Overall, 136 patients (62%) with symptomatic WM received therapy, whereas a watch-and-wait policy was adopted in 84 patients (38%) with asymptomatic WM. Among treated patients, first-line therapy consisted of chlorambucil in 93 cases (68%), cyclophosphamide-based regimens in 15 (11%) and nucleoside analogs-containing regimens in 17 (13%). Rituximab was associated to chemotherapy in 19 patients (14%). Details on therapy were not available in 11 cases (8%). Overall, 52 second cancers were observed in 49 patients (22%). Forty-six patients (94%) had one malignancy and 3 (6%) developed two cancers. The types of cancer were: gastrointestinal (n=9, 17%), lung (n=8, 15%), breast (n=7, 13%), urinary tract (n=6, 11%), prostate (n=5, 10%), diffuse large B cell lymphoma (n=5, 10%), myelodysplastic syndrome/acute leukemia (n=3, 6%), brain (n=3, 6%), thyroid (n=2, 4%), mouth (n=2, 4%), other cancers (n=2, 4%). The diagnosis of cancer preceded that of WM in 13 cases (27%), was concomitant (within 3 months) in 6 (12%) and subsequent in 30 (61%). The median time from diagnosis of WM to the occurrence of a subsequent cancer was 4.3 years (range: 0.2-12.9). The cumulative probability of developing a second cancer after WM was respectively 11% at 5 years, 21% at 10 years and 33% at 15 years. As compared to the control population, the risk of second cancer in WM was 1.66 times higher than expected (95% CI: 1.16-2.37, p=0.005), without significant difference between males and females (p=0.7). In multivariate analysis, the risk of second cancer was not influenced by age (p=0.91), sex (p=0.45), reduction of IgG (p=0.91) or IgA (p=0.58) levels. In a time-dependent analysis, therapy given for WM did not increase the risk of developing a second malignancy (hazard ratio: 1.12, p=0.76).

This study shows that WM are at higher risk of developing second cancers as compared to the general population. We did not find an association between the occurrence of second cancers and treatment of WM. Disease-related immune-suppression may predispose WM patients to develop other malignancies.

No relevant conflicts of interest to declare.