Is there an increased risk of second primary malignancies in older patients treated with lenalidomide?

Data from multiple clinical trials has indicated that patients with smoldering multiple myeloma and multiple myeloma (MM) treated with lenalidomide (lena), experienced an increased risk of developing second primary malignancies (SPM). However, these observations have not been reported consistently in all trials using lena as single-agent or in combination with other therapies.¹

In a study published in the Journal of Geriatric Oncology, Smith Giri and colleagues investigated whether this was a problem in the real-world setting when lena was administered as first-line therapy. They focused on older patients since they are usually underrepresented in clinical trials, and present with an inherent increased risk of prior and secondary malignancies.

Patients and methods

Data from the Surveillance, Epidemiology and End Results (SEER)-Medicare program were used. This program links the National Cancer Institute’s SEER registry with enrollment and claims data for Medicare and Medicaid services.

Patients (N = 9,850) ≥ 65 years with a histologically confirmed diagnosis of plasma cell myeloma between 2007 and 2015 were included in this study.

Patients were excluded if

• they had no available outpatient prescription records
• there was no prescription for anti-myeloma therapy within 90 days of diagnosis
• they had < 90 days of follow-up

First-line lena use was defined as initiation of lena within 90 days of diagnosis of myeloma. The key endpoint was the occurrence of SPM, which was defined as the occurrence of any malignancy > 90 days following myeloma diagnosis reported to a cancer registry.

Table 1. Baseline patient characteristics according to their exposure to lenalidomide as first-line therapy¹

 Key findings

Of the 9,850 patients enrolled, 67% were non-Hispanic Whites and the median age at diagnosis was 75 years with an interquartile range (IQR) of 70−80 years. Table 1 shows that in both groups at least 20% of patients had previous malignancies diagnosed. On average, patients receiving lena were more likely to be younger, non-Hispanic Whites than those who did not. A total of 60% of patients included had received lena at some point in their treatment, with 41% having received it as a first-line therapy.

 Table 2 shows the median follow-up time for all groups. The median duration of lena therapy was 11 months with patients receiving first-line lena being treated for a significantly increased duration (13 months; p < 0.01). The patients treated with lena at frontline were also associated with increased median survival (3.3 years versus 2.5 years).

Table 2. Effect of first-line lena treatment on OS¹

Secondary malignancies

Only 4.3% of patients developed SPM during the median 5-year follow-up (median latency of 19 months from myeloma diagnosis, 95% confidence interval [CI], 18−23 months). Out of the 423 patients that developed SPM, 362 had solid tumors and 61 presented with hematological malignancies. Table 3 shows the most common type of SPM including colorectal cancer, melanoma, breast, lung/bronchus, and AML/MDS.

Table 3. SPM type and incidence¹

SPM association with or without first-line lena treatment

There was no statistically significant difference in the incidence of any SPM at 5 years in patients receiving first-line lena treatment compared with non-receivers. The same result was found when comparing solid tumors and hematological cancers in patients treated with first-line lena and non-treated patients (Table 3).

When investigating the incidence rate of SPM, it was found that following lena treatment the incidence rate was 1.61 (95% CI, 1.42−1.82) per 100 person years. Patients not exposed to lena had an incidence rate of 2.00 (95% CI, 1.72−2.32) and the incidence ratio was 0.81 (95% CI, 0.66−0.98). However, after adjusting for age, sex, and race, the hazard ratio for SPM following lena treatment was not statistically significant. Similar results were achieved when analyzing solid or hematological malignancies separately.

Of note, patients undergoing autologous stem cell transplantation experience a higher risk of SPM due to the exposure to high-dose chemotherapy and the transplant process itself. Since this study analyzes only elderly patients receiving lena at frontline, most patients were ineligible for autologous stem cell transplantation and therefore, the vast majority did not receive either high-dose chemotherapy or lena maintenance. Moreover, the median follow-up of this trial might be too short to properly detect the incidence of SPM, but the 5-year overall survival estimate for the studied population was of 27.9% (95% CI, 26.8–28.9), (Table 2).

Conclusion

No clinically or statistically significant association was found between the use of first-line lena in older patients and an increased risk of developing SPM, either solid or hematological in origin. According to the SEER registry, the use of lena for newly diagnosed patients increased from 14.6% in 2007 to 52.6% in 2015, and this is the largest real-world study assessing this late toxicity in real-world situations.

These results should give elderly patients and clinicians confidence when receiving or prescribing immunomodulatory drug-based regimens for the treatment of multiple myeloma.