Table 3.
Summary of overall survival.
| Unweighted sample | IPTW-weighted samplea | |||||||
|---|---|---|---|---|---|---|---|---|
| Avapritinib | BAT | Estimate (95% CI) | p | Avapritinib | BAT | Estimate (95% CI) | p | |
| Number of unique patients | N = 176 | N = 141 | Effective N = 172 | Effective N = 136 | ||||
| Number of lines of therapy | N = 176 | N = 222 | Effective N = 172 | Effective N = 210 | ||||
| Deaths of unique patients, n (%) | 34 (19.3%) | 84 (59.6%) | – | – | 36 (20.9%) | 76 (55.9%) | – | – |
| Unique patients censored due to avapritinib initiation, n (%) | – | 21 (14.9%) | – | – | – | 25 (18.4%) | – | – |
| Unique patients censored due to new primary malignancy after the index date, n (%) | – | 6 (4.3%) | – | – | – | 8 (5.9%) | – | – |
| Mean follow-up (months) | 17.9 | 25.7 | – | – | 17.9 | 25.7 | – | – |
| Median overall survival (months) (95% CI) | NR (46.9, NE) | 23.4 (19.5, 32.6) | – | – | 49.0 (46.9, NE) | 26.8 (18.2, 39.7) | – | – |
| HR (95% CI)b | – | – | 0.39 (0.26, 0.58) | <0.001* | – | – | 0.48 (0.29, 0.79) | 0.004* |
| Survival rate | Log-rank p | Log-rank p | ||||||
| 3 months | 97.1% | 91.4% | – | 0.017* | 98.0% | 92.8% | – | 0.087 |
| 6 months | 94.7% | 83.0% | – | <0.001* | 96.4% | 84.8% | – | 0.006* |
| 9 months | 89.7% | 77.7% | – | 0.001* | 89.6% | 78.2% | – | 0.013* |
| 12 months | 87.3% | 72.0% | – | <0.001* | 86.4% | 73.8% | – | 0.013* |
| 18 months | 80.4% | 58.4% | – | <0.001* | 79.5% | 58.1% | – | <0.001* |
| 24 months | 77.5% | 49.2% | – | <0.001* | 74.5% | 50.9% | – | <0.001* |
| 30 months | 73.3% | 45.5% | – | <0.001* | 69.6% | 47.6% | – | <0.001* |
| 36 months | 70.7% | 40.1% | – | <0.001* | 67.9% | 42.7% | – | <0.001* |
| 48 months | 58.7% | 26.6% | – | <0.001* | 61.9% | 30.0% | – | <0.001* |
| 60 months | 50.3% | 20.2% | – | <0.001* | 36.8% | 23.4% | – | 0.001* |
AdvSM advanced systemic mastocytosis, BAT best available therapy, CI confidence interval, HR hazard ratio, IPTW inverse probability of treatment weighting, NE not estimable, NR not reached.
*p < 0.05.
aStabilized weights were generated using the following baseline characteristics: age, sex, region, ECOG score, anemia (hemoglobin <10 g/dl), thrombocytopenia (platelet count <100 × 109/l), AdvSM subtype, skin involvement, leukocyte count of 16 × 109/l or higher, serum tryptase level of 125 ng/ml or higher, number of mutated genes within the SRSF2/ASXL1/RUNX1 gene panel, number of prior lines of therapy, and prior use of tyrosine kinase inhibitor, cytoreductive, biologic or other systemic therapy.
bBoth unweighted and IPTW-weighted Cox proportional hazards models with a robust sandwich variance estimator were used to model overall survival. IPTW-weighted Cox proportional hazards model further adjusted for covariates with a standardized difference of greater than 10% after weighting, which included region, presence of thrombocytopenia at baseline, and prior use of tyrosine kinase inhibitor therapy, using a doubly robust approach.