MD Conference Express - ENDO 2015 - (Page 26)
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Lenvatinib targets particular fibroblast growth factor receptors, which might evoke unique responses. The
SELECT study was a phase 3 pivotal trial with a median
PFS (the primary end point) of 18.3 months for the
patients receiving lenvatinib (n = 261) and 3.6 months for
those receiving placebo (n = 131; HR, 0.21; 99% CI, 0.14 to
0.31; P < .001) [Schlumberger M et al. N Engl J Med. 2015].
PRs were achieved by 63% of patients receiving lenvatinib, and complete responses were achieved by 2%. AEs
led to dose reductions in 68% of patients and discontinuation in 14% of patients. Response to lenvatinib was not
predicted by RAS or BRAF mutations.
Notably, treatment with MKIs with angiogenic targets
can lead to the rare but dangerous and potentially fatal AEs
of bowel perforation and fistulas, bleeding in the tumor or
other organs, thromboembolism, and cardiac effects that
can include arrhythmias, coronary artery disease, and LV
dysfunction. These affect 1% to 2% of patients.
Ezra E.W. Cohen, MD, University of California San
Diego, La Jolla, California, USA, discussed the treatment
of MTC, which accounts for about 5% of thyroid cancers.
Distant metastases carry a poor prognosis with a median
overall survival (OS) of about 2 years. Among MTC, 75%
are sporadic and about 65% are RET mutated. Hereditary
MTC is almost universally RET mutated.
Patients with metastatic or recurrent disease that is
not curable do not necessarily require therapy and may
be better served by observation. Ideally, therapy should
be initiated when the patient has good performance
status, no to minimal symptoms, and evidence of disease progression within the last 6 to 12 months. Patients
who are symptomatic from their disease need systemic
therapy.
The MKIs vandetanib and cabozantinib offer meaningful therapeutic options for MTC. Vandetanib was
approved as a result of a phase 3 trial that met its primary end point of PFS [Wells SA et al. J Clin Oncol. 2012].
Patients with a RET mutation, particularly the M918T
mutation, had a tremendous benefit from vandetanib.
Vandetanib has a black box warning about QTc prolongation that occurred in 8% of patients who received it.
Cabozantinib is also approved for MTC, based on a
phase 3 trial [Elisei R et al. J Clin Oncol. 2013]. Among 219
patients who received cabozantinib, 94% showed target
lesion regression, whereas 27% of the 111 patients receiving placebo had target lesion regression. The median
PFS was 11.2 months for cabozantinib vs 4.0 months for
placebo (HR, 0.28; 95% CI, 0.19 to 0.40; P < .001). Patients
with the RET M918T mutation had a prolonged PFS relative to patients with other RET mutations (HR, 0.15; 95%
CI, 0.08 to 0.28) [Sherman SI et al. ASCO. 2013]. Patients
with RAS mutations also benefited from cabozantinib.
26
May 2015
Maria E. Cabanillas, MD, University of Texas MD
Anderson Cancer Center, Houston, Texas, USA, discussed
evidence to support salvage therapy after failure of a firstline kinase inhibitor in advanced thyroid cancer.
A retrospective review of adult patients with metastatic
DTC found that median OS was 24 months for patients
treated with sorafenib alone (n = 35) and 63 months for
those receiving salvage therapy (n = 25; P = .013) [Dadu R
et al. J Clin Endocrinol Metab. 2014]. PFS was 7.4 months
(n = 15; 95% CI, 3.1 to 11.3) for all patients treated with
sorafenib, and PFS was 11.3 months (n = 17; 95% CI, 5.3
to 24.4) for salvage therapy.
A phase 3 study of lenvatinib vs placebo in DTC found
that patients who were TKI-naïve had a PFS of 18.7
months with lenvatinib treatment (n = 229; 95% CI, 16.4
to not estimable), while TKI-pretreated patients had a
PFS of 15.1 months (n = 93; 95% CI, 8.8 to not estimable)
[Schlumberger M et al. N Engl J Med. 2015].
A phase 2 trial of vemurafenib in patients with papillary thyroid cancer found that vascular endothelial
growth factor receptor-2 inhibitor (VEGFR2i)-naïve
patients (n = 9) had a PR rate of 35%, median PFS of
15.6 months (95% CI, 11.2 to not reported), and OS not
reached [Brose MS et al. Eur J Cancer. 2013; (abstr 28)].
The VEGFR2i-pretreated patients (n = 6) had a PR rate
of 29%, median PFS of 6.3 months (95% CI, 5.39 to not
reported), and median OS of 9.8 months (95% CI, 7.39 to
not reached).
A phase 1 study of cabozantinib in DTC found that
patients previously treated with a VEGF pathway inhibitor still responded to cabozantinib [Cabanillas ME et al.
Thyroid. 2014].
In MTC, very little evidence exists for salvage therapy.
A phase 3 trial comparing cabozantinib vs placebo in 330
patients with metastatic MTC found that 43% of previously treated patients (19 of 44 patients) achieved a PR
with cabozantinib [Elisei R et al. J Clin Oncol. 2013]. A
retrospective study found that changing to a different,
but similar, TKI in MTC yielded responses that were quite
variable with a brief median time to failure [Weitzman SP
et al. ENDO. 2015].
Recent trials and drug approvals have led to new
options for advanced DTC and advanced MTC. Salvage
therapy can benefit patients whose first-line TKI has
failed, with greater evidence of benefit in DTC than MTC.
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MD Conference Express - ENDO 2015
MD Conference Express - ENDO 2015 - (Page Cover1)
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