Increases in the mean corpuscular volume (MCV) have been observed in patients with metastatic renal cell carcinoma (mRCC) on tyrosine kinase inhibitor (TKI) treatment; however, its association with progression‐free‐survival (PFS) is unknown. We aimed to characterize TKI‐associated macrocytosis in mRCC and its relationship with PFS. Retrospective review of data on macrocytosis and thyroid dysfunction on mRCC patients treated with sunitinib and/or sorafenib. These results are evaluated in the context of our previous report on the association of hypothyroidism in this setting. We assessed PFS as clinically defined by the treating physician. Seventy‐four patients, 29 of whom received both drugs, were included. A treatment period was defined as time from initiation to discontinuation of either sunitinib or sorafenib; 103 treatment periods [sorafenib (47), sunitinib (56)] were analyzed. Macrocytosis was found in 55 and 8% of sunitinib‐ and sorafenib‐treated patients, respectively, P < 0.001. The median time to developing macrocytosis was 3 months (m, range 1–7). Median PFS in sunitinib‐treated patients was 11 m (95% CI: 6–19). Median PFS was higher among those with macrocytosis compared to normocytosis (21 m [95% CI: 11–25] vs. 4 m [95% CI: 3–8] P = 0.0001). Macrocytosis and hypothyroidism were two significant predictors of PFS. The greatest difference in PFS among all patients was observed in patients with both macrocytosis and hypothyroidism (25 m), compared to the normocytic and euthyroid patients (5 m) (P < 0.0001). Sunitinib‐related macrocytosis was associated with prolonged PFS, and concurrent development of hypothyroidism and macrocytosis further prolonged PFS. Increased MCV may have a role as a predictive biomarker for sunitinib. Prospective studies accounting for other known prognostic factors are needed to confirm this finding.
453 Background: Increases in mean corpuscular volume (MCV) and hypothyroidism have been observed in patients on sunitinib treatment. We characterized tyrosine kinase-associated macrocytosis in metastatic renal cell carcinoma (mRCC) patients and its relationship, along with thyroid dysfunction, to progression-free survival (PFS). Methods: A retrospective chart review was performed on patients treated with sunitinib and/or sorafenib (01/2005-01/2011). Data pertaining to the development of macrocytosis was analyzed in association with our previous data on thyroid dysfunction in these patients. We assessed PFS, as clinically defined by the treating provider. Results: Seventy-four patients with 103 treatment periods for sorafenib (47) and sunitinib (56) were analyzed. Macrocytosis was found in 55% and 8% of sunitinib and sorafenib treatment periods, respectively (p<0.001). Focusing on the sunitinib-treated patients for all further analysis, the median PFS was 11 months (mo) (95% CI, 6-19). Median PFS was 21 mo (95% CI, 11-25) for patients who developed macrocytosis compared to 4 mo (95% CI, 3-8) in normocytic patients (p=0.0001). The time to development of macrocytosis did not affect the degree of macrocytosis observed (p=0.47). Macrocytosis and hypothyroidism were both significant predictors of prolonged PFS in our cohort. The greatest difference in PFS was noted between patients who developed both macrocytosis and hypothyroidism (25 mo) versus those who remained both normocytic and euthyroid (5 mo) (p<0.0001). Conclusions: Sunitinib-related macrocytosis is associated with a prolonged PFS in mRCC. The concurrent development of both hypothyroidism and macrocytosis in this setting was associated longer PFS compared to either alone. Increased MCV may be used as a biomarker for sunitinib response in this setting. [Table: see text]
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