Diagnostic delay in cancer is a difficult subject to study with many confounder factors. Several papers have been published with controversial results about the relationship between delay and survival, although there is a clear tendence for a worse prognosis with longer delays. We will expose some of the confounder factors and biases that can interact with the association between delay and survival.
The time between symptom recognition and a definitive diagnosis have been described in many terms including ‘Time-to-Diagnosis’ (TtD), delay to diagnosis, pre-diagnostic interval and duration of symptoms in the literature  and we will use TtD across this paper. The concept of the term “delay” assumes that there is an ideal period of time to arrive to a diagnosis in a patient with cancer
Letter published in the Journal of Clinical Oncology about a previous article where Time to Diagnosis (TtD) is not associated with outcome. We reply about the possibility of a “representativeness bias” because doctors relate bone pain in young adolescents with growth.
Cancer diagnosis is difficult in the primary care setting because many symptoms are common for tumors and benign conditions. This is more complicated with healthy patients or for young people.
A large analysis of data implemented in UK is the base for the development of a tool called “QCancer” , a model for men and women that estimate risks of multiple cancers according to baseline risk factors, patterns of symptoms and specific clinical conditions.