EXCELS study results do not rule out potential cancer risk with omalizumab Reply
To the Editor:
Although our data1 showed little association between omalizumab and the risk of malignancy, the issues raised by Li et al2 are reasonable concerns that highlight the limitations of the study design and the data. Li et al focus on 3 problems: (1) the inclusion of prevalent users, (2) the small proportion of patients with a history of cancer or premalignant condition, and (3) losses to follow-up.
As Li et al state, prevalent users could have a lower risk for malignancy than do new users if patients with early cancers discontinue use or if cancer risk is high soon after use begins and then declines. If we exclude all prevalent users from the study population, the adjusted hazard ratio for all malignancy in the new users was 1.12, a value very close to the hazard ratio of 1.09 that we reported for all study subjects....