400 patients a year have cancer with 'unknown starting point'
Around 400 patients a year who are diagnosed with cancer with no obvious starting point continue to have a poor prognosis despite some improvement in survival, a new report has revealed.
It appears as a cancer that has spread to areas such as the liver, lungs and bones.
These cases, known as cancer of unknown primary site, can be difficult to treat as a result, the report from the National Cancer Registry of Ireland shows.
The number of cases and deaths per year are broadly similar between the sexes, although incidence and mortality rates are slightly higher in men. The age of diagnosis on average is 77 years for women and 73 for men.
Currently, two-thirds of all patients are diagnosed pathologically - which is arrived at by an examination of the substance and function of the tissues of the body.
This is up from just half of all cases in the mid to late 1990s, said the report.
"Due to the aggressive clinical course of these cancers, mortality rates are high with approximately seven deaths for every 10 cases diagnosed.
"Incidence rates have fallen significantly over time by over 5pc a year due in large part to improvements in the quality and specificity of cancer diagnoses since the mid-1990s. Mortality rates have also fallen significantly, by over 3pc per year, in both men and women."
More than two-thirds of patients do not receive any tumour-directed therapy for their cancer, although patients may have palliative therapy to relieve symptoms.
"By contrast, patients with metastatic cancers from known primary sites have a very different treatment profile, with a much lower percentage of these patients, at 32pc, not having treatment," it said. "Patients with metastatic disease whose primary site is known are more likely to have surgery, 20pc versus 5pc, chemotherapy, 20pc versus 45pc, and radiotherapy, 18pc versus 29pc."
It said that "despite some improvement in survival rates over time, patients diagnosed with cancer of unknown primary have a median survival time of less than three months and current five-year net survival rates are just 13pc".
The significant decline in incidence and mortality rates over time are positive indications of the improvements in diagnostic methods and treatments overall for all cancers, the report added.