Impact of Comorbidities and Body Mass Index in Myelofibrosis Patients Treated with Ruxolitinib: A Retrospective Analysis

Background: Comorbidities and body mass index (BMI) are significantly associated with outcome in patients (pts) who receive continue treatment with tyrosine kinase inhibitors (TKIs), such as in Ph+ leukemias. Ruxolitinib (RUX) is the first JAK1/2 inhibitor that may induce spleen/symptom responses and improve quality of life in pts with myelofibrosis (MF). Up-to-date, no data are available on the impact of comorbidities and BMI on pts treated with RUX.

Aims: To evaluate the impact of comorbidities and BMI on responses, overall survival (OS) and maintenance of RUX dose in a large cohort of pts.

Methods: Data were extracted from an electronic database that included retrospective data on pts treated before January 2015 in 16 Italian Hematology centers. Response to RUX was evaluated according to IWG-MRT criteria. BMI was calculated at the time of start of RUX and classified according to WHO criteria. Comorbidities were recorded at the time of start of RUX and classified according to the Charlson Comorbidity Index (CCI). Overall survival (OS) was calculated from the date of RUX start to the time of death or to last follow-up, whichever came first.

Results: Between June 2011 and Apr 2016, 289 pts with PMF (52.6%), or PET-MF (17%) or PPV-MF (30.4%) were treated with RUX in participating Centers. At RUX start, median age was 68.4 years (range 39-89) with a male prevalence (56.4%); International Prognostic Score System (IPSS) was intermediate (intm)-1 (15.6%), intm-2 (45.3%), high (39.1%). Transfusion dependence and spleen enlargement were present in 26.6% and 96.9% of pts, respectively (69.6% with spleen≥ 10 cm). Median total symptom score (TSS) was 20 (range 0-70). JAK2^V617F was present in 80.3% of 234 evaluable pts. Median follow-up from MF diagnosis was 3.8 yr (range 0.3-29.6) and median RUX exposure was 20 months (3-56.2).

Overall, comorbidities were evaluable in 275 pts. CCI stratification showed the absence of comorbidities in 100 pts (36.4%), one comorbidity in 63 pts (22.9%) and two or more in 112 pts (40.7%). Compared to pts with CCI <2, pts with CCI ≥2 were more frequently: male (66.1% vs 49.1%, p=0.005), ≥65y (74.1% vs 54%, p=0.001), at intm2/high IPSS risk (90.2% vs 81%, p=0.03) and transfusion-dependent (36.6% vs 20.2%, p=0.003). Notably, the percentage of pts starting RUX >2y from MF diagnosis was lower if CCI≥2 (33.9% vs 54%, p=0.001).

Higher CCI did not correlate with lower spleen response (achieved by 45.2% vs 34.7%, p=0.09), TSS response (90.1% vs 83.2%, p=0.11), and higher incidence of RUX-induced anemia (Hb <10 g/dl in pts with baseline Hb ≥10 g/dl) (48% vs 41%, p=0.33). RUX starting and titrated doses at 12-wks were similar in the two groups (p=0.44 and p=0.81, respectively).

OS was significantly higher in pts with CCI<2 (96.7% vs 87.8% at 2 yr, p<0.001). After stratification according to CCI (below or above 2) and the achievement of a spleen response, both factors remained significantly associated with survival. Indeed, in pts with CCI<2 OS at 2 yr was 92.7% and 79.1%, depending on the achievement of a spleen response (SR) or not (NR), respectively (p=0.034). Analogously, in pts with CCI≥2 the achievement of a spleen response significantly increased survival (79.2% vs 55.3% in pts without spleen response, p=0.011). Notably, OS was comparable in pts with lower CCI /no spleen response and in pts with higher CCI/spleen response (79.1% vs 79.2%) (Figure 1).

BMI was evaluable in 269 pts: 169 pts (62.8%) were classified as under-weight/normal for a BMI <25, whereas 100 pts were overweight/obese (BMI ≥25). Pts with BMI≥25 were more frequently male (71% vs 47.3%, p<0.001) and with a lower incidence of anemia (30% vs 42%, p=0.049). BMI stratification did not correlate with differences in spleen response (p=0.83) and TSS (p=0.18) or onset of anemia/infections during treatment (p=0.49 and p=0.28). Starting and median doses, as well as percentage of pts reducing RUX dose over time, were similar in the two groups.

Summary: In MF pts treated with RUX, BMI and comorbidities did not influence the achievement of spleen/symptom responses, maintenance of RUX dose or onset of drug-related anemia. Although CCI stratification correlated with survival, as in Ph+ leukemias treated with TKIs, the achievement of a spleen response was able to counterbalance the negative prognostic effect of a higher CCI. Consequently, higher BMI and CCI should not be regarded as contraindication to RUX therapy.

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