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Phlebotomy and hydroxyurea improve OS, reduce thrombosis risk in polycythemia vera
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Therapeutic phlebotomy and hydroxyurea improved OS and reduced risk for thrombosis among older adults with polycythemia vera at high risk for thrombotic events, according to retrospective study results.
However, less than two-thirds of patients underwent these recommended treatments.
“Both treatment modalities were underused, as only 64% underwent therapeutic phlebotomy and 60.6% received hydroxyurea,” Nikolai A. Podoltsev, MD, PhD, assistant professor in the hematology section of the department of medicine and associate program director of the hematology/oncology fellowship program at Yale University School of Medicine, told HemOnc Today. “Our study adds to the evidence supporting current National Comprehensive Cancer Network and European LeukemiaNet guideline recommendations and emphasizes the need to follow them.”
Podoltsev and colleagues used the SEER database to identify 820 patients (median age, 77 years; interquartile range, 71-83; 57% women; 91.2% white) newly diagnosed with polycythemia vera between 2007 and 2013. Follow-up continued until Dec. 31, 2014, or death, whichever occurred first.
Patients who had at least one phlebotomy claim between diagnosis and the end of follow-up were designated as phlebotomy users.
Investigators used Medicare Part D claims to acquire information about hydroxyurea use after diagnosis. They calculated hydroxyurea proportion of days covered as the percentage of days covered by hydroxyurea prescriptions from diagnosis to the end of follow-up.
OS and occurrence of a thrombotic event after polycythemia vera diagnosis served as key outcome measures.
During the study, 41.1% of patients (n = 336) were treated with both phlebotomy and hydroxyurea, 23% (n = 189) were treated with phlebotomy only, 19.6% (n = 161) received hydroxyurea only, and 16.3% (n = 134) received neither therapy.
Phlebotomy users had a median seven phlebotomies (interquartile range [IQR], 3-12) from diagnosis to the end of follow-up, with a median phlebotomy intensity of 2.3 (IQR, 1.1-4.1). Among hydroxyurea users, the median hydroxyurea proportion of days covered was 61.6% (IQR, 35.2-80.1).
After median follow-up of 2.83 years, 37.2% (n = 305) of all patients died. Phlebotomy survived a median 6.29 years, whereas phlebotomy nonusers survived a median 4.5 years (P < .01).
Multivariable Cox regression analyses showed patients who underwent phlebotomy had a significantly lower mortality risk (HR = 0.65; 95% CI, 0.51-0.81) than those who did not undergo phlebotomy.
Increased phlebotomy intensity appeared associated with reduced risk for death (HR = 0.71; 95% CI, 0.65-0.79).
With every 10% increase of hydroxyurea proportion of days covered, the researchers observed an 8% to 9% decrease in mortality risk (HR = 0.92; 95% CI, 0.89-0.95 in model with phlebotomy as a binary variable; HR = 0.91; 95% CI, 0.88-0.94 in model that included intensity of phlebotomy). Other factors associated with significantly increased risk for death included older age, male sex, presence of at least one comorbidity, and possible underuse of the health care system as indicated by not receiving an influenza vaccination.
phlebotomy nonusers, 29.3% (n = 142) of phlebotomy users, 45.4% (n = 178) of hydroxyurea nonusers and 27.6% (n = 118) of hydroxyurea users.
Higher hydroxyurea proportion of days covered was associated with a lower risk for thrombotic events, as were phlebotomy (HR = 0.52; 95% CI, 0.42-0.66) and increasing phlebotomy intensity (HR = 0.46; 95% CI, 0.29-0.74).
“Our study highlights the value of adhering to polycythemia vera treatment guidelines,” Podoltsev said in a press release. “Use of the two recommended treatments saves lives.” – by Jennifer Byrne
For more information:
Nikolai Podoltsev, MD, PhD, can be reached at nikolai.podoltsev@yale.edu.
Disclosures: Podoltsev reports no relevant disclosures. Please see the study for all other authors’ relevant financial disclosures.
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