Lenalidomide is an oral IMiD®, immunomodulatory compound, approved for use in combination with dexamethasone (Len/Dex) in patients with RRMM who have received one prior therapy. Len/Dex is indicated until evidence of disease progression at the best-tolerated dose of both Len and Dex (Dimopoulos et al. Leukemia
2011). However, the tolerability profile of long term exposure to Len/Dex is not well described, and evidence that long term exposure to Len/Dex would improve on the response rate and survival has yet to be determined.
We sought to determine the efficacy and safety profile of long term exposure to Len/Dex in RRMM pts in a multicentre study.
Method. We retrospectively reviewed the medical records of 50 RRMM pts treated with Len/Dex and remaining on Len for ≥2 years with a special focus on pts receiving Len for ≥3 years. All pts included had complete follow up records.
Results. The median (range min-max) age was 58 years (39-79) with 30% (n=15) > 65 years (elderly MM), the sex ratio M/F was 1.2, 49% (n=24) ISS 2 and 3, 12% (n=6) severe renal insufficiency (CrCl < 30mL/min), and 8% (n=4) adverse FISH [del17p and/or t(4 ;14)]. Overall, 25 pts (50%) had Len/Dex at first relapse, 19 pts (38%) at second relapse and 6 (9%) pts in subsequent relapses. Len/Dex was given at first relapse in 10 (66%) elderly patients. The median time from diagnosis to starting Len/Dex was 4.5 years (1-16) for overall cohort and 3 years (1-8) for elderly patients (p=0.05). 28 pts (56%) received Len/Dex for ≥3 years. The median duration on Len/Dex was 3 (2-7) years for the overall cohort, and was 4 (3;7) years for patients exposed to Len ≥3 years. Treatment duration was similar across age categories and across number of previous relapses. With a median follow up of 4 years, 19 patients had stopped Len/Dex.
The response rate (ORR, ≥PR) was 96% (n=48), including 37 (74%) patients with ≥VGPR, similar across age categories. Interestingly, the ORR and ≥VGPR were similar irrespective of whether patients have stopped Len/Dex in our study. The ORR was also similar across number of previous relapses, but the ≥VGPR rate was lower in patients at third relapse and beyond, (50%; p=ns). The ORR and ≥VGPR rate was 93% and 77% in patients exposed to Len ≥3 years, similar to the whole cohort. The median time to first response and best response were 2 (1-5) months and 4.5 (2-9) months, respectively. Overall, 9 (18%) patients stopped treatment due to toxicity, 9 (18%) progression of MM, and 1 (0.5%) patient decision. With a median follow up of 4 years, the median (95%CI) TTP was not reached, the estimated 4-yr TTP was 51.5%. There was no imbalance in the incidence of toxicity based on age, number of previous relapses, and patients exposed to Len ≥3 years did not discontinue more often due to toxicity, 14% versus 19% for those receiving Len < 3 years.
The hematological safety profile was similar across age categories, number of previous relapses, and patients exposed to Len ≥ 3 years; overall, 8 (16%) patients experienced grade 3-4 neutropenia, 6% thrombopenia, and 6% anemia. Ten (20%) patients experienced a thromboembolic event (VTE), all of them of venous type. Two patients had previous history of VTE, but none of them experienced VTE on Len/Dex, likely related to adequate VTE prophylaxis. The median time to first occurrence was 5 (1;28) months, although 4/10 occurred in patients with ≥3 years on Len. All VTE occurred while on VTE prophylaxis except for 1 patient, 5 on aspirin, 2 on prophylactic doses of LMWH, and 2 on VKA (target INR 2-3). The incidence rate of second primary malignancy (SPM) was 3 (6%) (larynx, lung, and MDS). The SPMs occurred at a median time of 4 years from start of Len, while Len was already stopped in 2/3 patients, the latter stopped len at time SPM was diagnosed. Interestingly, none of the patients with more than 3 years exposure on Len had SPM.
Conclusions: The current study provides estimates of responses, TTP and safety in a series of MM pts with long-term exposure to Len-based regimen at relapse. 62% of patients remained on Len beyond 3 years reflecting the efficacy and good safety profile of Len in relapsed MM, irrespective of age and number of prior therapies. Furthermore, no excess of long term side effects, including SPM, was observed with a prolonged long follow-up in this study.