In this retrospective study we updated our results with the use of TKIs for thyroid cancer treatment after 10 years of experience [14]. Considering all lines of treatment, 32% of patients from our cohort achieved an OR, and the PFS and OS rates were 32 and 39 months, respectively. Our results coincide with other institutional experiences [15–25] and this real-world data serve to guide the discussions within the medical team and with the patients regarding the initiation of systemic therapy in RR-DTC.
In our cohort, patients who received sorafenib demonstrated an ORR of 9%. This aligns with findings from other real-world studies, which have reported ORRs ranging from 11–25% [14–17], as well as with results from the DECISION trial, where patients exhibited a PR of 12% without any CRs [3]. In contrast, our group of patients treated with lenvatinib exhibited a lower ORR compared to what was reported in the SELECT phase III study and in non-trial settings (ranging from 33–69%) [4, 18–25]. One plausible explanation for this difference could be that more than half of our patient cohort received lenvatinib after progressing on first-line sorafenib. Indeed, studies with a higher proportion of TKI-naïve patients have reported higher ORRs (62%-64%) [18, 19], whereas those including more non-naïve TKI patients reported ORRs similar to ours (ranging from 31–38%) [21, 23–25]. Additionally, observational studies tend to enroll patients with Eastern Cooperative Oncology Group Performance Status (ECOG PS) ≥ 3, more comorbidities, and patients who did not start treatment at full dose [18–25]. Indeed, a previous analysis from our cohort revealed that in a subgroup of patients meeting the SELECT trial inclusion criteria, the PR with lenvatinib increased from 36% in the total cohort to 50% [26].
In line with the aforementioned findings, it was anticipated that the ORR in our cohort would be significantly higher in the lenvatinib group compared to the sorafenib group (37.9% vs. 9.4%, p = 0.008). Although no prospective randomized comparative analysis between sorafenib and lenvatinib has been published, a few retrospective studies have aimed to compare these two tyrosine kinase inhibitors (TKIs) [27, 28]. Ito et al. demonstrated a superior ORR in patients treated with lenvatinib compared to those receiving sorafenib (65% vs. 22%, p = 0.015) in a cohort of 18 and 21 patients, respectively [27]. Subsequently, Kim et al., in a larger multicenter retrospective cohort study, also reported a higher ORR in the lenvatinib group (59% vs. 24%, p < 0.001) [28]
The median progression-free survival (PFS) observed with sorafenib (15 months) and lenvatinib (22 months) in our study aligns closely with findings reported in both clinical trials and real-world studies [3, 4, 14–25]. In the DECISION trial, the median PFS following sorafenib treatment was reported as 10.8 months [3], while observational cohorts reported a range from 8 to 22 months [14–17]. Similarly, the median PFS in the SELECT trial was 18.3 months [4], with real-world studies reporting a range of 10 to 18 months [18–25]. Although lenvatinib appears to demonstrate superior PFS compared to sorafenib, our analysis did not reach statistical significance. In contrast to our findings, the retrospective study by Kim et al. demonstrated a significantly longer PFS with lenvatinib compared to sorafenib after adjusting for multiple confounding factors (35 vs. 13 months, p = 0.001) [28]. One potential explanation for the disparity between our results and theirs is that our study included a higher proportion of patients who received second-line lenvatinib. Notably, in the SELECT trial, patients with prior TKI exposure exhibited lower PFS rates compared to TKI-naïve patients (15 months) [4]. However, our analysis did not find a significant difference when comparing first- and second-line lenvatinib. Furthermore, while we did not adjust for variables between groups due to sample size limitations, the duration of treatment and time to progression prior to TKI initiation were similar between patients treated with lenvatinib and sorafenib.
The adverse event (AE) profiles of sorafenib and lenvatinib observed in our study were consistent with findings from clinical trials and other retrospective cohorts [3, 4, 14–25]. Both tyrosine kinase inhibitors (TKIs) exhibited high percentages of AEs (97% with sorafenib and 100% with lenvatinib) and serious AEs (56% with sorafenib and 65% with lenvatinib), with no statistical difference observed between the groups. Furthermore, both TKIs demonstrated similar frequencies of dose reductions, interruptions, and withdrawals. However, patients treated with sorafenib showed higher frequencies of hand-foot skin syndrome (69% vs. 41%, p = 0.032) and alopecia (25% vs. 3%, p = 0.018) compared to those receiving lenvatinib. Conversely, the frequency of proteinuria was 31% in patients receiving lenvatinib compared to 0% in those receiving sorafenib (p < 0.001). These findings are consistent with other studies comparing the adverse event profiles of sorafenib and lenvatinib in differentiated thyroid cancer (DTC) patients [27–29].
Of note, although the frequency of hypertension was not significantly different between the lenvatinib and the sorafenib and groups (72 vs. 59%, p = 0.284), the occurrence of grade 3 or 4 hypertension was significantly higher in patients receiving lenvatinib (31 vs 9%, p = 0.034). Unlike our study, Asian studies found that patients treated with lenvatinib exhibited a higher incidence of all-grades hypertension compared to those treated with sorafenib [27–29]. This difference may be attributed to the relatively high incidence of hypertension reported in Asian cohorts (78%-95%) compared to Caucasians, which is associated with lower body mass [27–29]. Indeed, the frequency of hypertension in our cohort (73%) was similar to that reported in the SELECT trial (68%).
Our study has several limitations that warrant consideration. Firstly, being a retrospective study, it inherently carries a selection bias, potentially influencing the generalizability of our findings. Furthermore, although efforts were made to mitigate confounding factors, the sorafenib and lenvatinib treatment groups were not directly comparable due to the retrospective nature of the study. Despite similarities in median treatment duration and time of progression prior to TKI initiation between the two groups, residual confounding cannot be entirely ruled out. Additionally, the sample size in our study is relatively small compared to other institutional experiences [17, 19, 23], which may limit the statistical power and generalizability of our results. However, it's worth noting that our study represents the largest single-center experience with TKIs in Latin America, contributing valuable insights into the management of thyroid cancer in this region.
In conclusion, our study demonstrated that tumoral responses and PFS with TKIs in RR-DTC were similar to other real-world data. While lenvatinib exhibited a higher ORR compared to sorafenib, there is no significant difference in terms of PFS or DoR between the two drugs. The incidence of hand-foot skin syndrome and alopecia was observed to be higher among patients receiving sorafenib, whereas proteinuria was more common in those treated with lenvatinib. These results underscore the importance of considering both efficacy and tolerability profiles when selecting the appropriate TKI therapy for individual patients. By providing valuable insights into the real-world outcomes of TKI treatments, our study may assist clinicians in making informed decisions regarding treatment sequencing and optimizing patient care.