The following material has been sourced from the Australian Institute of Health and Welfare
Cancer of unknown primary site incorporates ICD-10 cancer codes: Incidence C80 (Malignant neoplasm without specification of site); mortality C77–C80 (C77: Secondary and unspecified malignant neoplasm of lymph nodes, C78: Secondary malignant neoplasm of respiratory and digestive organs, C79: Secondary malignant neoplasm of other and unspecified sites; C80: Malignant neoplasm without specification of site), C97 (Malignant neoplasms of independent primary multiple sites).
New cases
In 2021, there were 2,681 new cases of cancer of unknown primary site diagnosed in Australia (1,406 males and 1,275 females). In 2025, it is estimated that 2,633 new cases of cancer of unknown primary site will be diagnosed in Australia (1,423 males and 1,210 females). In 2025, it is estimated that a person has a 1 in 148 (or 0.68%) risk of being diagnosed with cancer of unknown primary site by the age of 85 (1 in 132 or 0.76% for males and 1 in 167 or 0.60% for females).
Graph: statistics-cancer-unknown-primary-figure-1-estimated-cancer-incidence-persons-2025
In 2021, the age-standardised incidence rate was 11 cases per 100,000 persons (13 for males and 9.3 for females). In 2025, it is estimated that the age-standardised incidence rate will be 9.5 cases per 100,000 persons (11 for males and 7.9 for females). The incidence rate for cancer of unknown primary site is expected to increase with age.
Graph: statistics-cancer-unknown-primary-figure-2-age-standardised-incidence-rates
The number of new cases of cancer of unknown primary site diagnosed increased from 2,141 (1,118 males and 1,023 females) in 1982 to 2,681 in 2021. Over the same period, the age-standardised incidence rate decreased from 24 cases per 100,000 persons (28 for males and 20 for females) in 1982 to 11 cases per 100,000 persons in 2021.
Deaths
In 2021, cancer of unknown primary site was the sixth most common cause of cancer death in Australia. It is estimated that it will be the eighth most common cause of death from cancer in 2025.
In 2023, there were 2,803 deaths from cancer of unknown primary site in Australia (1,565 males and 1,238 females). In 2025, it is estimated that there will be 2,933 deaths (1,645 males and 1,288 females). In 2025, it is estimated that a person has a 1 in 137 (or 0.73%) risk of dying from cancer of unknown primary site by the age of 85 (1 in 118 or 0.85% for males and 1 in 163 or 0.61% for females).
Graph: statistics-cancer-unknown-primary-figure-3-estimated-cancer-mortality-persons-2025
In 2023, the age-standardised mortality rate was 11 deaths per 100,000 persons (13 for males and 8.6 for females). In 2025, it is estimated that the age-standardised mortality rate will be 11 deaths per 100,000 persons (13 for males and 8.4 for females). The mortality rate for cancer of unknown primary site is expected to increase with age.
Graph: statistics-cancer-unknown-primary-figure-4-age-standardised-mortality-rates
The number of deaths from cancer of unknown primary site increased from 1,202 (609 males and 593 females) in 1982 to 2,803 in 2023. Over the same period, the age-standardised mortality rate decreased from 13 deaths per 100,000 persons (16 for males and 12 for females) in 1982 to 11 deaths per 100,000 persons in 2023.
Survival
In 2017–2021, individuals diagnosed with cancer of unknown primary site had a 13% chance (15% for males and 11% for females) of surviving for five years compared to their counterparts in the general Australian population. Between 1987–1991 and 2017–2021, five-year relative survival for cancer of unknown primary site improved from 6.3% to 13%.
Graph: statistics-cancer-unknown-primary-figure-5-5-year-relative-survival
Prevalence
At the end of 2021, there were 1,079 people living who had been diagnosed with cancer of unknown primary site that year, 2,984 people living who had been diagnosed with cancer of unknown primary site in the previous 5 years (from 2017 to 2021) and 7,782 people living who had been diagnosed with cancer of unknown primary site in the previous 40 years (from 1982 to 2021).
For more information on cancer data, see the NCCI website
The National Cancer Control Indicators (NCCI) are a set of indicators across the continuum of cancer care, from Prevention and Screening through to Diagnosis, Treatment, Psychosocial care, Research and Outcomes. The NCCI website allows users to see visual representations of data on each indicator through interactive charts.
