The escalation package by Kristian Brock. Documentation
is hosted at https://brockk.github.io/escalation/
To provide dose selection decisions, the escalation
package daisy-chains together objects that support a common interface,
each deriving from type selector. This vignette
demonstrates the entire interface supported by selector
objects. For the purpose of illustratration, we use a BOIN selector but
the same functions will work on every type of dose selector in
escalation.
library(escalation)
#> Loading required package: magrittrTarget toxicity rate:
tox_target(fit)
#> [1] 0.3The number of patients treated:
num_patients(fit)
#> [1] 8Cohort IDs for the treated patients:
cohort(fit)
#> [1] 1 1 2 2 3 3 4 4The code infers from the spaces in the outcome string that a dose-decision was made after the second, fourth , and sixth patients.
Integers representing the dose-levels given:
doses_given(fit)
#> [1] 1 1 2 2 3 3 2 2Bits representing whether toxicity event was observed:
tox(fit)
#> [1] 0 0 0 0 0 1 0 1The total number of toxicities seen at all doses combined:
num_tox(fit)
#> [1] 2A data-frame containing the above information:
model_frame(fit)
#> # A tibble: 8 × 4
#> patient cohort dose tox
#> <int> <int> <int> <int>
#> 1 1 1 1 0
#> 2 2 1 1 0
#> 3 3 2 2 0
#> 4 4 2 2 0
#> 5 5 3 3 0
#> 6 6 3 3 1
#> 7 7 4 2 0
#> 8 8 4 2 1The number of doses under investigation:
num_doses(fit)
#> [1] 5The indices of the dose-levels under investigation:
dose_indices(fit)
#> [1] 1 2 3 4 5The dose-level recommended for the next patient:
recommended_dose(fit)
#> [1] 2After seeing some toxicity at doses 2 and 3, the design sensibly sticks at dose 2 for the time being.
A logical value for whether accrual should continue:
continue(fit)
#> [1] TRUEWe infer from this that no stopping condition has yet been triggered.
The number of patients treated at each dose:
n_at_dose(fit)
#> [1] 2 4 2 0 0The number of patients treated at the recommended dose:
n_at_recommended_dose(fit)
#> [1] 4The proportion of patients treated at each dose:
prob_administer(fit)
#> 1 2 3 4 5
#> 0.25 0.50 0.25 0.00 0.00The total number of toxicities seen at each dose:
tox_at_dose(fit)
#> [1] 0 1 1 0 0The empirical toxicity rate, i.e. the number of toxicities divided by the number of patients:
empiric_tox_rate(fit)
#> [1] 0.00 0.25 0.50 NaN NaNThe model-derived expected toxicity rate at each dose:
mean_prob_tox(fit)
#> [1] 0.02 0.26 0.50 NA NAThe BOIN design makes no estimate for doses it has not yet administered.
The model-derived median toxicity rate at each dose:
median_prob_tox(fit)
#> 1 2 3 4 5
#> 0.01 0.21 0.50 NA NABOIN does not actually calculate posterior median estimates. Sometimes it will be necessary to return missing values if functionality is not supported by a model. Median estimates could be added to the BOIN class in due course.
The model-derived quantile of the toxicity rate at each dose:
prob_tox_quantile(fit, 0.9)
#> 1 2 3 4 5
#> 0.05 0.54 0.89 NA NABOIN does not calculate this either. It could also be added.
The posterior probability that the toxicity rate exceeds some threshold value, here 50%:
prob_tox_exceeds(fit, 0.5)
#> [1] 0.009391185 0.129051871 0.500000000 NA NAOnce again, no estimate is made for non-administered doses. We see that the model estimates a trivial chance that the toxicity rate at the lowest dose exceeds 50%.
Learn if this model supports sampling from the posterior:
supports_sampling(fit)
#> [1] FALSEThe BOIN model does not support sampling. If it did, we could run
prob_tox_samples(fit).
We can also call some standard generic functions:
print(fit)
#> Patient-level data:
#> # A tibble: 8 × 4
#> Patient Cohort Dose Tox
#> <int> <int> <int> <int>
#> 1 1 1 1 0
#> 2 2 1 1 0
#> 3 3 2 2 0
#> 4 4 2 2 0
#> 5 5 3 3 0
#> 6 6 3 3 1
#> 7 7 4 2 0
#> 8 8 4 2 1
#>
#> Dose-level data:
#> # A tibble: 6 × 8
#> dose tox n empiric_tox_rate mean_prob_tox median_prob_tox admissible
#> <ord> <dbl> <dbl> <dbl> <dbl> <dbl> <lgl>
#> 1 NoDose 0 0 0 0 0 TRUE
#> 2 1 0 2 0 0.02 0.01 TRUE
#> 3 2 1 4 0.25 0.26 0.21 TRUE
#> 4 3 1 2 0.5 0.5 0.5 TRUE
#> 5 4 0 0 NaN NA NA TRUE
#> 6 5 0 0 NaN NA NA TRUE
#> # ℹ 1 more variable: recommended <lgl>
#>
#> The model targets a toxicity level of 0.3.
#> The model advocates continuing at dose 2.
summary(fit)
#> # A tibble: 6 × 8
#> dose tox n empiric_tox_rate mean_prob_tox median_prob_tox admissible
#> <ord> <dbl> <dbl> <dbl> <dbl> <dbl> <lgl>
#> 1 NoDose 0 0 0 0 0 TRUE
#> 2 1 0 2 0 0.02 0.01 TRUE
#> 3 2 1 4 0.25 0.26 0.21 TRUE
#> 4 3 1 2 0.5 0.5 0.5 TRUE
#> 5 4 0 0 NaN NA NA TRUE
#> 6 5 0 0 NaN NA NA TRUE
#> # ℹ 1 more variable: recommended <lgl>and cast it to a tidyverse tibble:
library(tibble)
as_tibble(fit)
#> # A tibble: 6 × 8
#> dose tox n empiric_tox_rate mean_prob_tox median_prob_tox admissible
#> <ord> <dbl> <dbl> <dbl> <dbl> <dbl> <lgl>
#> 1 NoDose 0 0 0 0 0 TRUE
#> 2 1 0 2 0 0.02 0.01 TRUE
#> 3 2 1 4 0.25 0.26 0.21 TRUE
#> 4 3 1 2 0.5 0.5 0.5 TRUE
#> 5 4 0 0 NaN NA NA TRUE
#> 6 5 0 0 NaN NA NA TRUE
#> # ℹ 1 more variable: recommended <lgl>