title: Evidence of increasing mortality with longer diagnostic intervals for five common cancers: a cohort study in primary care.
abstract: BACKGROUND
  Early diagnosis is considered a key factor in improving the outcomes in cancer therapy; it remains unclear, however, whether long pre-diagnostic patient pathways influence clinical outcomes negatively. The aim of this study was to assess the association between the length of the diagnostic interval and the five-year mortality for the five most common cancers in Denmark while addressing known biases.
  
  
  METHODS
  A total of 1128 patients with colorectal, lung, melanoma skin, breast or prostate cancer were included in a prospective, population-based study in a Danish county. The diagnostic interval was defined as the time from the first presentation of symptoms in primary care till the date of diagnosis. Each type of cancer was analysed separately and combined, and all analyses were stratified according to the general practitioner's (GP's) interpretation of the presenting symptoms. We used conditional logistic regression to estimate five-year mortality odds ratios as a function of the diagnostic interval using restricted cubic splines and adjusting for comorbidity, age, sex and type of cancer.
  
  
  RESULTS
  We found increasing mortality with longer diagnostic intervals among the approximately 40% of the patients who presented in primary care with symptoms suggestive of cancer or any other serious illness. In the same group, very short diagnostic intervals were also associated with increased mortality. Patients presenting with vague symptoms not directly related to cancer or any other serious illness had longer diagnostic intervals and the same survival probability as those who presented with cancer suspicious/serious symptoms. For the former, we found no statistically significant association between the length of the diagnostic interval and mortality.
  
  
  CONCLUSIONS
  In full coherence with clinical logic, the healthcare system instigates prompt investigation of seriously ill patients. This likely explains the counter-intuitive findings of high mortality with short diagnostic intervals; but it does not explain the increasing mortality with longer diagnostic intervals. Thus, the study provides further evidence for the hypothesis that the length of the diagnostic interval affects mortality negatively.
authors: The Research Unit for General Practice, Research Centre for Cancer Diagnosis in Primary Care, Aarhus University, Denmark; Department of Public Health - Section for General Medical Practice, Aarhus University, Denmark; Department of Culture and Society - Section for Anthropology, Aarhus University, Denmark. Electronic address: mlt@alm.au.dk.
authors: Marie Louise
authors: ML
authors: Tørring
authors: Department of Public Health - Section for Biostatistics, Aarhus University, Denmark.
authors: Morten
authors: M
authors: Frydenberg
authors: The Research Unit for General Practice, Research Centre for Cancer Diagnosis in Primary Care, Aarhus University, Denmark.
authors: Rikke P
authors: RP
authors: Hansen
authors: The Research Unit for General Practice, Research Centre for Cancer Diagnosis in Primary Care, Aarhus University, Denmark.
authors: Frede
authors: F
authors: Olesen
authors: The Research Unit for General Practice, Research Centre for Cancer Diagnosis in Primary Care, Aarhus University, Denmark.
authors: Peter
authors: P
authors: Vedsted
mesh_terms: D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D017668:Age of Onset; D000368:Aged; D001943:Breast Neoplasms / Q000175:diagnosis / Q000401:mortality*; D015331:Cohort Studies; D015179:Colorectal Neoplasms / Q000175:diagnosis / Q000401:mortality*; D015897:Comorbidity; D057210:Delayed Diagnosis / Q000401:mortality; D003718:Denmark / Q000453:epidemiology; D055088:Early Detection of Cancer / Q000401:mortality; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000175:diagnosis / Q000401:mortality*; D008297:Male; D008545:Melanoma / Q000175:diagnosis / Q000401:mortality*; D008875:Middle Aged; D011320:Primary Health Care; D011446:Prospective Studies; D011471:Prostatic Neoplasms / Q000175:diagnosis / Q000401:mortality*; D017678:Sex Distribution; D012878:Skin Neoplasms / Q000175:diagnosis / Q000401:mortality*; D055815:Young Adult