A Researcher Is Studying the Likely Occurrence Rate of Secondary

A researcher is studying the likely occurrence rate of secondary cancers after a new schedule of chemotherapy for childhood leukemia, using a biochemical marker obtained by blood draw 6 months after the initiation of chemotherapy. What is the rationale for using this biological marker as a proximate outcome, rather than counting the actual rate of secondary cancers?

A) It could be psychologically harmful to children and families to have researchers following up in the future to ask whether the child has had a cancer recurrence.
B) The final end point is not obtainable over a reasonable span of time, since secondary cancers can occur at any age through late adulthood.
C) There is no viable rationale for this decision. Most proximate end points are unreliable variables and should not be used unless there are no final end points.
D) The researcher is not interested in whether children suffer a secondary malignancy; the researcher is merely interested in the biological marker's value.