How to remove specific number of events in a tbl_regression (gtsummary package)

Question

I'm using tbl_regression from the gtsummary package to show the results of cox proportional hazards models. Due to circumstances regarding sensitive personal information, I am not allowed to show strata with a number of observations less than 5. I can, however, still show the estimates, CIs etc. for those strata, but not how many persons have had the event if the number is less than 5. In these number of events strata with less than 5 observations, I would like to insert just a line to indicate this.

From what I have read, the modify_table_body function is perhaps the correct function to achieve this. However, I cannot manage to find out how to use it correctly. Is there any way to define that the regression table should not show N_event less than 5 but still show HRs, CIs, person years ect. for those given stratas? Below is my preliminary code in which I thought maybe should be followed by "%>% modify_table_body()".

Thank you in advance for your help!

Best, Mathilde

cox_cat_cns2 <- coxph(Surv(TTD_year, Dod_status) ~ Highest_Edu_Household + Diag_year + Age_household_mom_num + Age_household_dad_num + Country_origin_household, data = data_cox_cat_cns)

cox_cat_cns_adj_table <- tbl_regression(cox_cat_cns2,
     label = c(Highest_Edu_Household ~ "Highest parental education",
               Diag_year ~ "Year of diagnosis",
               Age_household_mom_num ~ "Mother's age at diagnosis",
               Age_household_dad_num ~ "Father's age at diagnosis",
               Country_origin_household ~ "Parents' country of origin"),
     exponentiate = TRUE) %>%
     add_nevent(location = "level") %>%
     bold_labels() %>%
     italicize_levels() %>%
     modify_table_styling(
            columns = estimate,
            rows = reference_row %in% TRUE,
            missing_symbol = "Ref.") %>%
     modify_footnote(everything() ~ NA, abbreviation = TRUE) %>%
     modify_table_styling(
            column = p.value,
            hide = TRUE) %>%
     modify_header(
            label = "",
            stat_nevent = "**Events (N)**",
            exposure ~ "**Person years**")

Answer 1

You can 1. define a new function to "style" the number of events that collapses any counts less than 5 as "<5", then 2. use that function to style the column in the resulting table. Example below!

library(gtsummary)
#> #Uighur
library(survival)
library(dplyr)

style_number5 <- function(x, ...) {
  ifelse(
    x < 5, 
    paste0("<", style_number(5, ...)),
    style_number(x, ...)
  )
}

style_number5(4:6)
#> [1] "<5" "5"  "6"


tbl <- 
  trial %>%
  slice(1:45) %>%
  coxph(Surv(ttdeath, death) ~ stage, data = .) %>%
  tbl_regression(exponentiate = TRUE) %>%
  add_nevent(location = "level") %>%
  modify_fmt_fun(stat_nevent ~ style_number5)

^{Created on 2022-04-21 by the reprex package (v2.0.1)}