Early Development of Ubiquitous Acanthocytosis and Extravascular Hemolysis in Lung Cancer Patients Receiving Alectinib

Abstract

Alectinib is a standard initial treatment for patients with advanced anaplastic lymphoma kinase (ALK) rearranged non-small-cell lung cancer (NSCLC). The current study analyzed a prospective cohort of 24 consecutive alectinib-treated patients and controls in order to comprehensively characterize longitudinal erythrocyte changes under treatment with ALK inhibitors. Upon starting alectinib, all examined patients developed reticulocytosis and abnormal erythrocyte morphology with anisocytosis and a predominance of acanthocytes (64% of red blood cells on average, range 36−100%) in the peripheral blood smear within approximately 2 weeks. Changes were accompanied by a gradual reduction in Eosin-5-maleimide (EMA) binding, which became pathologic (<80% of cells) within 1−2 months in all cases, mimicking an abortive form of hereditary spherocytosis. The latter could be ruled out in 3/3 of analyzed cases by normal sequencing results for the ANK1, EPB42, SLC4A1, SPTA1, or SBTB genes. The direct Coombs test was also negative in 11/11 tested cases. Besides, anemia, increased LDH, and increased bilirubin were noted in a fraction of patients only, ranging between 42 and 68%. Furthermore, haptoglobin decreases were infrequent, occurring in approximately 1/3 of cases only, and mild, with an average value of 0.93 g/L within the normal range of 0.3−2 g/dL, suggesting that hemolysis occurred predominantly in the extravascular compartment, likely due to splenic trapping of the deformed erythrocytes. These changes showed no association with progression-free survival under alectinib or molecular features, i.e., ALK fusion variant or TP53 status of the disease, and resolved upon a switch to an alternative ALK inhibitor. Thus, alectinib induces mild, reversible erythrocyte changes in practically all treated patients, whose most sensitive signs are aberrant red cell morphology in the peripheral smear, a pathologic EMA test, and reactive reticulocytosis. Frank hemolytic anemia is rare, but mild subclinical hemolysis is very frequent and poses differential-diagnostic problems. Alectinib can be continued under the regular control of hemolysis parameters, but the risk of long-term complications, such as cholelithiasis due to increased serum bilirubin in most patients, remains unclear at present.

Keywords: ALK+ NSCLC; acanthocytosis; alectinib; anemia; hemolysis.

Figure 1

Development of peripheral blood changes after the start of alectinib in ALK+ NSCLC. (a) Peripheral blood film of patient 8 (Table 1) at 67× magnification showing normal red cell morphology before alectinib start. (b) Peripheral blood film two weeks after alectinib start at 67× magnification showing abnormal red cell morphology with anisocytosis, a predominance of acanthocytes, as well as occasional echinocytes, spherocytes, and rare fragmentocytes (Table 1). (c) EMA binding assay of the same patient before therapy with alectinib showing a 10% decrease in EMA fluorescence (reference range <20%). (d) In the same patient, six weeks after alectinib start, EMA fluorescence is reduced by 58%. (e) Changes in hemoglobin (Hb, in g/dL, n = 16), red-cell distribution width (RDW, %, n = 17), serum lactate dehydrogenase (LDH, in U/mL/10, n = 16), total serum bilirubin (bili, in mg/dL, n = 11), blood reticulocytes (reti, %, n = 18), as well as levels of serum haptoglobin (Hp, in g/L, n = 19) and after start of alectinib in our patients. Statistical comparisons were performed with a paired t-test for parameters with available data before and after alectinib start (Hb, RDW, LDH, bilirubin) or using a t-test comparison vs. the upper or lower limit of the normal range for other parameters (5–15% for reticulocytes, and 0.3–2.0 g/L for haptoglobin). Box plots indicate mean values with their standard errors (from left to right: 13.8 g/dL vs. 12.0 g/dL, 13.4% vs. 16.8%, 136 U/L vs.234 U/L, 0.45 mg/dL vs.1.26 mg/dL, 43% with p < 0.0001 compared to the normal range, 0.93 g/L within the normal range of 0.3–2.0 g/L); ns: not statistically significant. (f) The percentage of patients with abnormal values for each of the parameters analyzed in this study, according to Table 1. Bars indicate percentages with 95% confidence intervals: 68.4% [43.5–87.4] for reduced serum hemoglobin, 15.8% [3.4–39.6] for increased RDW, 42.1% [20.2–66.5] for increased serum LDH, 57.9% [33.5–79.8] for increased serum bilirubin, 100% [82.4–100] for increased blood reticulocytes, 36.8% [16.3–61.6] for reduced serum haptoglobin, 100% [82.4–100] for reduced EMA binding, and 100% [71.5–100] for the presence of abnormalities in the blood smear, while the mean percentage of acanthocytes in the peripheral blood smear was 65.8% [48.6–83.1].

Figure 1

Development of peripheral blood changes after the start of alectinib in ALK+ NSCLC. (a) Peripheral blood film of patient 8 (Table 1) at 67× magnification showing normal red cell morphology before alectinib start. (b) Peripheral blood film two weeks after alectinib start at 67× magnification showing abnormal red cell morphology with anisocytosis, a predominance of acanthocytes, as well as occasional echinocytes, spherocytes, and rare fragmentocytes (Table 1). (c) EMA binding assay of the same patient before therapy with alectinib showing a 10% decrease in EMA fluorescence (reference range <20%). (d) In the same patient, six weeks after alectinib start, EMA fluorescence is reduced by 58%. (e) Changes in hemoglobin (Hb, in g/dL, n = 16), red-cell distribution width (RDW, %, n = 17), serum lactate dehydrogenase (LDH, in U/mL/10, n = 16), total serum bilirubin (bili, in mg/dL, n = 11), blood reticulocytes (reti, %, n = 18), as well as levels of serum haptoglobin (Hp, in g/L, n = 19) and after start of alectinib in our patients. Statistical comparisons were performed with a paired t-test for parameters with available data before and after alectinib start (Hb, RDW, LDH, bilirubin) or using a t-test comparison vs. the upper or lower limit of the normal range for other parameters (5–15% for reticulocytes, and 0.3–2.0 g/L for haptoglobin). Box plots indicate mean values with their standard errors (from left to right: 13.8 g/dL vs. 12.0 g/dL, 13.4% vs. 16.8%, 136 U/L vs.234 U/L, 0.45 mg/dL vs.1.26 mg/dL, 43% with p < 0.0001 compared to the normal range, 0.93 g/L within the normal range of 0.3–2.0 g/L); ns: not statistically significant. (f) The percentage of patients with abnormal values for each of the parameters analyzed in this study, according to Table 1. Bars indicate percentages with 95% confidence intervals: 68.4% [43.5–87.4] for reduced serum hemoglobin, 15.8% [3.4–39.6] for increased RDW, 42.1% [20.2–66.5] for increased serum LDH, 57.9% [33.5–79.8] for increased serum bilirubin, 100% [82.4–100] for increased blood reticulocytes, 36.8% [16.3–61.6] for reduced serum haptoglobin, 100% [82.4–100] for reduced EMA binding, and 100% [71.5–100] for the presence of abnormalities in the blood smear, while the mean percentage of acanthocytes in the peripheral blood smear was 65.8% [48.6–83.1].

Figure 2

Resolution of erythrocyte changes after alectinib stop in patient 1 (Table 1). (a) Peripheral blood film at 100× magnification showing abnormal red cell morphology during therapy with alectinib. (b) Blood smear 4 weeks after the switching of therapy to brigatinib at 100× magnification with the return of some normal erythrocytes. (c–e) Longitudinal resolution or improvement of other changes in the same patient after alectinib stop; BL: baseline; 4 w: 4 weeks after treatment stop; 2 m: 2 months after treatment stop.

Figure 2

Resolution of erythrocyte changes after alectinib stop in patient 1 (Table 1). (a) Peripheral blood film at 100× magnification showing abnormal red cell morphology during therapy with alectinib. (b) Blood smear 4 weeks after the switching of therapy to brigatinib at 100× magnification with the return of some normal erythrocytes. (c–e) Longitudinal resolution or improvement of other changes in the same patient after alectinib stop; BL: baseline; 4 w: 4 weeks after treatment stop; 2 m: 2 months after treatment stop.