We thank Dr. Luo and Dr. Li for providing comments regarding our manuscript entitled “Efficacy of modified FOLFOX6 chemotherapy for patients with unresectable pseudomyxoma peritonei”.

They proposed that our study was a retrospective cohort study rather than a retrospective case series, and cited the description proposed by Dr. Dekker et al. [1]. From their distinguishing method between cohort studies and case series [1], our study meets the characteristic of cohort study: the patients were sampled on the basis of exposure, not a specific outcome, and followed over time to assess the occurrence of the outcomes. This description would be a nice candidate method to distinguish between cohort studies and case series, however, we do not think that this description has been completely regarded as a world-wide consensus.

For example, some researchers proposed that cohort studies differ from case series in that a comparison group is used for analysis of the treatment outcomes [2, 3]. In addition, the Strengthening the Reporting of Observational Studies in the Epidemiology (STROBE) recommendations refer to three main study designs including cohort, case–control, and cross-sectional studies, but do not specifically address case reports and case series [4]. The definition of case series has thus remained to be fully determined.

Taken together, at present, we consider that our study is not out of a case series. We completely agree with Dr. Luo and Dr. Li that the distinction between cohort studies and case series needs to be clarified in the future.