Outcomes of Patients with Myelodysplastic Syndromes (MDS) Who Achieve Stable Disease after Treatment with Hypomethylating Agents (HMA)

Background

The primary treatment goal in higher-risk MDS patients (pts) is to prolong survival by altering the natural history of the disease and delaying progression to acute myeloid leukemia (AML). Treatment with HMA such as azacitidine (AZA) improves overall survival (OS) in pts who achieve a response of stable disease (SD) or better (complete remission [CR], partial remission [PR], or hematologic improvement [HI]) (Gore et al, Haematologica, 2013). However, it is not well established if pts who achieve SD by 6 months (mo) of therapy should be offered different therapies to optimize their response or continue with the same HMA regimen.

Methods

Clinical data were obtained from the MDS Clinical Research Consortium database. Pts treated with either AZA or decitabine (DAC) were included and categorized per the Revised International Prognostic Scoring System. Responses were evaluated per International Working Group (IWG 2006) criteria. SD was defined as no evidence of progression and without achievement of HI. Early response was defined as achievement of CR, PR, HI, or SD between 3-6 months (mo) of therapy. Best response was assessed after 6 mo of treatment. OS was calculated from the start of therapy to date of death or last follow up. Differences were evaluated using the Fisher-exact test and Mann-Whitney U tests for categorical and continuous variables, respectively.

Results

Of 291 pts with higher-risk MDS and available response data, 248 (85%) received treatment with AZA and 43 (15%) with DAC. Median age was 70 years (range, 35-99), median absolute neutrophil count (ANC) was 1.05 X10⁹/L (range, .58-68), hemoglobin 9.3 g/dL (range, 3.7-14.3), platelets 73 X10⁹/L (range, 4-659), and bone marrow blasts 10% (range, 0-19). Per IPSS-R, 20% of pts were intermediate risk, 37% high, and 43% very high. A total of 142 pts (49%) progressed to AML. Median time from diagnosis to start of HMA was 28 days. Early responses (3-6 mo) were: CR 10%, PR 5%, HI 10%, and SD 49%. Among the 144 pts who achieved SD at 3-6 mo, 29 (20%) achieved a better response (CR, PR, or HI) later during their treatment, with a median time to better response of 3.7 mo (range,1.2-14.5); 113 (89%) remained with stable disease, and 2 (1%) progressed to AML.

With a median follow up of 16.5 mo (range, 2.5-120.2), the median OS by best response at any time point during therapy: CR 19.7 mo, PR 12.6 mo, HI 15.4 mo, and SD 13.8 mo. Pts who achieved CR had superior OS compared to SD (p=.03) but similar survival compared to pts who achieved PR (p=.45) or HI (p=.24).

Of 29 pts with SD who achieved a better response > 6 mo, 16 (55%) achieved a CR and 13 (45%) achieved a PR or HI. Pts with SD who subsequently achieved CR had superior OS compared to pts who remained in SD (28.1 vs 14.4 mo, respectively, p=.04), while pts who subsequently achieved PR or HI had a similar survival compared to pts who remained in SD (12.1 vs 14.4 mo, respectively, p=.81).

Conclusion

Among MDS pts treated with HMAs, 20% who have SD at initial assessment go on to have a better response later in their treatment course, However, only 11% of SD pts achieved a CR thereafter, which predicted better OS. Thus, pts who achieve SD by 6 mo should be offered a clinical trial with novel agents to improve their chances of achieving CR. If a clinical trial is not available, pts should remain on HMA therapy until disease progression.