New research suggests that for some patients with cancer, especially brain tumors and small-cell-lung cancer, the first manifestation is a psychiatric symptom.

The results indicate that in the month after a first evaluation for a psychiatric symptom, the odds of being diagnosed with any malignancy increased by 2.61-fold, according to the report in the International Journal of Cancer. For brain tumors, however, the likelihood of cancer diagnosis was much higher: 18.85-fold.

“We studied the occurrence of cancer in persons with newly diagnosed mental illness to investigate whether a group of patients exists in which the symptoms of the psychiatric disease are associated with cancer or a paraneoplastic syndrome,” Dr. Michael E. Benros, from the University of Aarhus, Denmark, and colleagues note.

Using data from the Danish Psychiatric Central Register and the Danish Cancer Registry, Benros’ team assessed the occurrence of psychiatric symptoms and cancer in more than 4 million subjects who were followed from 1994 to 2003.

During the study period, 202,144 subjects had a first-time psychiatric contact and 208,995 were diagnosed with cancer. One of every 63 subjects over 50 years of age was diagnosed with cancer within 1 year of a first-time psychiatric contact.

As noted, the strongest association was with brain tumors, although a high risk of small-cell lung cancer was also noted with an incidence rate ratio of 6.13.

In general, beyond 3 months, the association between psychiatric symptoms and cancer diagnosis disappeared. The exception was brain tumors for which an elevated risk was still apparent within 9 months of first-time psychiatric contact.

“Clinicians should be aware that in patients, particularly older patients with first-onset psychiatric disorders, the psychiatric symptoms could be a sign of a yet undetected cancer,” the authors conclude.

SOURCE: International Journal of Cancer, June 15, 2009.