Cancer of unknown primary: a population-based analysis of temporal change and socioeconomic disparities.

BACKGROUND: Cancer of unknown primary (CUP) is the fourth most common cause of cancer death. With advanced diagnostics and treatments, we investigated the proportion of cancers diagnosed as CUP, treatment outcomes and association with socioeconomic disparities. METHODS: We analysed trends in CUP diagnosis and outcome within the Surveillance, Epidemiology, and End Results registry between 1973 and 2008. RESULTS: The percentage of all cancers diagnosed as CUP has decreased over time comprising <2% of cancers since 2007. A higher proportion of CUP was diagnosed in the elderly, females, blacks and residents of less affluent or less educated counties. Median survival of all CUP patients was 3 months, with no improvement over time. The 5-year survival significantly improved in those with squamous histology (squamous cell carcinoma; SCC) but only marginally in non-SCC. Factors associated with a longer survival on multivariate analysis included white race; female; <65 years old; most recent decade at diagnosis; SCC; married; a histological diagnosis; and treatment with radiotherapy (all P<0.001). Despite the improvement in survival with radiotherapy, its use was less frequent in females and blacks. CONCLUSION: The percentage of cancers diagnosed as CUP is decreasing but prognosis remains poor, particularly in non-SCC CUP. However, significant socioeconomic disparities exist in diagnosis and survival, suggesting inequalities in access to diagnostic investigations and treatment.

Second primary cancers after cancer of unknown primary in Sweden and Germany: efficacy of the modern work-up.

In unsparing efforts to find the hidden primaries, second primary cancers (SPCs) unrelated to cancer of unknown primary (CUP) are found. The detection rates of SPCs after CUP can be considered as measures for the effectiveness of modern diagnostic techniques in finding tumors. We aimed to compare the rates of specific SPCs found after the work-up of CUP and the more sign/symptom-directed diagnostic approaches applied after any other cancer. The number of CUP patients identified in the nationwide Swedish database and nine German cancer registries was 24 641 from 1997 through 2006, and rate ratios (RRs) for SPCs were recorded in two follow-up periods. The detection rate of SPCs immediately after any other cancer was about two times higher in Germany than in Sweden, but the rate immediately after CUP was almost the same for the two datasets. In the joint analyses after CUP, the RRs of liver, lung, breast, and kidney cancers were higher than after any other cancer, whereas the RRs of prostate, urinary bladder, and connective tissue cancers as well as non-Hodgkin's lymphoma were not significantly different; the RR of cancers of upper aerodigestive tract was lower after CUP than after any other cancer. The joint data indicate that the work-up is efficient in detecting tumors in the thoracoabdominal organs that are screened by computed tomography. For some other organ sites, the more sign/symptom-directed diagnostic approaches may be equally efficient. However, none of the applied techniques could detect all tumors immediately after the first diagnosis.

Racial differences in ill defined cancer mortality in the United States and in the District of Columbia.

STUDY OBJECTIVE: The aim was to examine the epidemiology of unknown primary cancer mortality in the USA during 1979 to 1988 by age, sex, race, year, and geographical area. DESIGN: National (US) and state data were abstracted for deaths due to ill defined cancer (ICD-9 195.0 to 199.1) and all cancers combined (ICD-9 140.0-209.9). Age adjusted mortality rates were calculated using the 1980 USA population as the standard, and standardised rate ratios were derived. National total cancer incidence data were obtained from the surveillance, epidemiology and end results (SEER) program, and age and sex specific relative (black/white) cancer incidence rates were derived and compared to relative (black/white) mortality rates for ill defined cancer. State and regional median family income levels were obtained from the 1980 census and compared to corresponding mortality rates. SETTING: This study used data for the US population, the 50 states, and the District of Columbia. MEASUREMENTS AND MAIN RESULTS: During 1984-1988, ill defined cancers accounted for an average of 34,921 deaths each year in the USA (13.7 per 100,000 population). The mortality rate due to ill defined cancers is greater among blacks (19.3 per 100,000) than whites (13.2 per 100,000) (RR = 1.5) and has not declined since 1979. There is considerable geographical variation in the ill defined cancer mortality rate. Thus among blacks the highest rates were clustered in the central states (23 per 100,000) and the lowest rates were seen in the mountain and western states (17 per 100,000). The District of Columbia had the highest overall rate (21.7 per 100,000) when compared to all other states. The black/white relative mortality rate due to ill defined cancer was consistently greater than the black/white relative incidence of all cancers. CONCLUSIONS: Ill defined cancer mortality is the fourth leading site of cancer mortality in the USA, and accounts for 7.4% of cancer deaths annually. The large proportion of ill defined cancer deaths may have biased the accuracy of national and local cancer incidence and mortality statistics. The higher mortality of ill defined cancer among blacks is not explained by the higher overall cancer incidence among blacks and suggests the influence of socioeconomic or cultural barriers that may result in underutilisation of health services or substandard health care. Ill defined cancer mortality may be a sentinel indicator of deficiencies in the health care delivery system as well as a measure of progress against cancer.