Efficacy and Safety of Ruxolitinib in the Treatment of Elderly Patients with Policythemia Vera Resistant/Intolerant to Hydroxyurea

Introduction: Ruxolitinib (Rux) has been recently approved as second-line therapy in patients (pts) with Polycythemia Vera (PV) resistant/intolerant to hydroxyurea (HU). Median age of PV pts enrolled in the pivotal Response trials was around 60 yrs; at present, no data is reported on the use of Rux in elderly pts.

Aims: In a real-world cohort of PV pts treated with Rux, we investigated whether the efficacy and safety of Rux were comparable in pts who initiated therapy when aged ≥75 years compared with younger pts.

Methods: After IRB approval, clinical/laboratory data of 934 WHO2016-defined PV pts followed in 29 Hematology Centers were retrospectively collected. Of them, 168 (17.9%) were considered resistant/intolerant to HU at any time during follow-up by responsible physician and shifted to Rux as second-line therapy.

Results: Among the 168 pts treated with Rux, 42 (25%, median age 78.2 years) were aged ≥75 yrs at Rux start, 74 (44%, median age 67.7) were aged 60-74 and 52 (31%, median age 53) were <60 at Rux start.

No significant differences were observed between the 3 groups, apart from a lower need for phlebotomies in pts aged ≥75 yrs and lower presence of palpable spleen in older pts (age ≥60), that more frequently switched to Rux due to HU intolerance (Table 1).

Median duration of HU treatment was 41.0 months (IQR 14.6 - 85.8), with a trend for a longer median treatment duration in pts aged ≥75 [61.0 months (IQR 21.5 - 89.6) vs 35.9 months (IQR 13.4 - 79.6), p=0.04]. Rux starting dose was similar across age groups; however, more elderly pts underwent Rux dose reductions during follow-up (45.2% in pts aged ≥75 vs 28.6% in younger pts, p=0.04).

Responses during Rux therapy are reported in Table 2, with no significant differences between the 3 groups at any time. In the overall cohort, response on PV-related symptoms at 6 and 12 months was significantly higher in pts who switched to Rux because of HU intolerance; however, this difference was not observed in pts aged ≥75 yrs.

As to the most common hematologic Rux-related toxicities, grade 3-4 anemia and thrombocytopenia were observed in only 2 (1.2%) and 5 (3%) pts, with no difference across age groups (p=0.45 and p=0.18). However, any grade anemia and thrombocytopenia during Rux were more frequently observed in pts aged ≥75 (68.3% vs 51.7% of anemia, p=0.06 and 12.2% vs 3.5% of thrombocytopenia in younger pts, p=0.04). Nineteen and 4 pts experienced infectious and thrombotic complications during Rux with incidence rates of 0.59 and 0.12 per 100 patient-months, respectively, comparably in younger and older (≥75) pts (p=0.75 and p=0.29, respectively). Notably, 6 infections were herpes simplex/zoster virus, comparably distributed between the 3 groups (p=0.60).

Permanent Rux discontinuation was needed in 14 pts (8.3%) after a median Rux exposure of 7.8 months (IQR 4.6 - 17.6) (incidence: 0.41 per 100 pts/months). Discontinuation was comparable between age groups, with Rux stop in 4 pts aged ≥75 yrs and 10 younger pts (2.4% vs 5.2% at 8 months, log-rank p=0.75). At last follow-up, 2 pts had died (1 from 2 ^nd neoplasia after 19.1 months from Rux start and 1 from acute leukemia after 3.3 years), both pts aged 60-74 yrs.

Conclusions. In this real-world analysis, use of Rux in HU resistant/intolerant elderly PV pts was effective and safe despite the more frequent need for dose reductions. Older age should not discourage Rux therapy, but stricter hematological monitoring may be suggested.

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