Note: if you use this selector, it almost certainly needs to be the last
example in the chain - see Example below. This method selects dose by the
algorithm for identifying the optimal biological dose (OBD) described in Lin
et al. (2020). This class is intended to be used when a BOIN12 trial has
reached its maximum sample size. Thus, it intends to make the final dose
recommendation after the regular BOIN12 dose selection algorithm, as
implemented by get_boin12, has gracefully concluded a
dose-finding trial. However, the class can be used in any scenario where
there is a limit toxicity rate. See Examples. Note - this class will not
override the parent dose selector when the parent is advocating no dose. Thus
this class will not reinstate a dangerous dose.
select_boin12_obd(
parent_selector_factory,
when = c("finally", "always"),
tox_limit = NULL,
...
)Object of type selector_factory.
Either of: 'finally' to select dose only when the parent dose-selector has finished, by returning continue() == FALSE; or 'always' to use this dose-selection algorithm for every dose decision. As per the authors' original intentions, the default is 'finally'.
We seek a dose with toxicity probability no greater than. If not provided, the value will be sought from the parent dose-selector.
Extra args are ignored.
an object of type selector_factory.
Lin, R., Zhou, Y., Yan, F., Li, D., & Yuan, Y. (2020). BOIN12: Bayesian optimal interval phase I/II trial design for utility-based dose finding in immunotherapy and targeted therapies. JCO precision oncology, 4, 1393-1402.
# This class is intended to make the final dose selection in a BOIN12 trial:
tox_limit <- 0.35
model <- get_boin12(num_doses = 5, phi_t = 0.35, phi_e = 0.25,
u2 = 40, u3 = 60, n_star = 6) %>%
stop_at_n(n = 12) %>%
select_boin12_obd()
outcomes <- '1NNN 2NTN 2NNN 3NTT'
model %>% fit(outcomes) %>% recommended_dose()
#> [1] 1
# However, since behaviour is modular in this package, we can use this method
# to select dose at every dose decision:
model2 <- get_boin12(num_doses = 5, phi_t = 0.35, phi_e = 0.25,
u2 = 40, u3 = 60, n_star = 6) %>%
select_boin12_obd(when = 'always')
model2 %>% fit('1NNT') %>% recommended_dose()
#> [1] 1
model2 %>% fit('1NNN 2NNT') %>% recommended_dose()
#> [1] 1