One study  of 248 caregivers of terminally ill cancer patients investigated the presence of predeath complicated grief and its correlates. Results revealed the following variables associated with higher levels of predeath complicated grief:
Hydrazine sulfate is a chemical compound that has been studied as a treatment for cancer and certain side effects caused by cancer (see Question 1).
Hydrazine sulfate may block the tumor from taking in glucose, which is a type of sugar that tumor cells need to grow (see Question 3).
In randomized clinical trials (a type of research study), hydrazine sulfate did not make tumors shrink or go away. In some randomized trials, however, hydrazine sulfate was reported to be helpful in treating...
Other research has focused on predictors of outcomes such as symptoms of depression and overall negative health consequences. Three categories of variables have been investigated:
Situational (e.g., circumstances of the death).
Personal (e.g., personality characteristics, gender).
Interpersonal context (e.g., social support, kinship).
Most research has focused on spousal/partner loss and is not uniquely focused on death via cancer.
Situational: Expected or Unexpected Death
Although theory suggests that a sudden, unexpected loss should lead to more difficult grief, empirical findings have been mixed. The impact of an unexpected loss seems to be moderated by self-esteem and perceived control: Bereaved persons with low self-esteem and/or a sense that life is uncontrollable seem to suffer more depression and somatic complaints after an unexpected death than do bereaved persons with higher self-esteem and/or a sense of control.
Personal: Personality Characteristics
Attachment theory  has suggested that the nature of one's earliest attachments (typically with parents) predicts how one would react to loss. Bereaved persons with secure attachment styles would be least likely to experience complicated grief, while those with either insecure styles or anxious-ambivalent styles would be most likely to experience negative outcomes.
In a study of 59 caregivers of terminally ill spouses, the nature of their attachment styles and marital quality were evaluated. Results showed that caregivers with insecure attachment styles or in marriages that were "security-increasing" were more likely to experience symptoms of complicated grief. Persons with a tendency toward "ruminative coping," a pattern of excessively focusing on one's symptoms of distress, have also been shown to experience extended depression after a loss.