In recent years, immunotherapy has gained growing importance in oncology and, immune checkpoint inhibitors (ICIs), specifically, have become a crucial component of the treatment algorithms of several types of advanced solid tumors (Luo et al., 2021). With more than 1,000 ongoing trials, immunotherapy is also the most promising area of cancer research (UCLA Health, 2021).

Although the efficacy and safety profile of ICIs (alone or in combination with other agents) have been tested in several trials, some features related to ICIs use are still unclear. One of the most important unmet clinical needs is their duration of treatment. Early trials on immunotherapy suggested that ICIs should be continued until disease progression, evidence of clinical benefit, unacceptable toxicity (whichever came first), or up to two years (Marron et al., 2021, Robert et al., 2020a). However, the optimal treatment duration for ICIs remains to be established. The commonly used two-year cut-off came from indirect comparison between the results of different early trials. Accumulating data question the role of fixed-duration immunotherapy in patients achieving a response to treatment (Marron et al., 2021, Robert et al., 2020a, Shukla et al., 2021). However, the majority of studies comparing fixed (up to two years) or continuous immunotherapy (treatment allowed beyond two years) are based on retrospective experiences on a single tumor type, and suffer small sample sizes (Marron et al., 2021, Robert et al., 2020a, Shukla et al., 2021). From the evidence so far, it is not possible to answer the question whether immunotherapy “should be continued ad infinitum” in patients who obtain a response or stabilization of the disease (Smith et al., 2020).

To assess the impact of immunotherapy duration on oncologic outcomes, we ran this systematic review and meta-analysis aiming to establish whether ICIs can be safely discontinued at completion of two years of active treatment across different types of solid tumors.