Chapter 29: Cancer survival in Izmir, Turkey, 1995-1997

Eser S

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Abstract

The Izmir cancer registry, is the first population-based cancer registry in Turkey, was established in 1992. Cancer registration is now done by active methods. The registry contributed data on survival for 12 cancer sites or types registered in 1995–1997. Follow-up was predominantly done by active methods with median follow-up ranging between 17–72 months for different cancers. The proportion with histologically verified diagnosis for various cancers ranged between 84–100%; there were no death certificate only cases (DCOs); 98–100% of total registered cases were included for the survival analysis. Complete follow-up at five years ranged from 79–98% for different cancers. Five-year age-standardized relative survival rates of common cancers were breast (77%), urinary bladder (70%), larynx (69%), colon (53%), rectum (52%), non-Hodgkin lymphoma (50%) and cervix (58%). Five-year relative survival by age group portrayed decreasing survival with increasing age at diagnosis for cancer of the cervix, and was fluctuating for other cancers. Decreasing survival with increasing clinical extent of disease was also noted.


Izmir cancer registry

The Izmir cancer registry was the first population-based cancer registry in Turkey, established in 1992 by the Ministry of Health and Ege University, in collaboration with the Turkish–American Collaboration for Health Research and Programming, University of Massachusetts at the Izmir provincial health directorate. The Ministry of Health had earlier established a passive cancer registration system for the entire country in 1983, which ended registering one fourth of expected cancers. Cancer registration is now done by active methods. Over 40 sources of registration, comprising government and private sector hospitals, clinics, pathology laboratories and hospices, are visited for data collection from the hospital cancer registries and other medical records. The registry covers an area of 11 530 km2, of the entire Izmir province and caters to a population of about 3.3 million in 1998 with a sex ratio of 985 females to 1000 males. The average annual age-standardized incidence rate is 157 per 100 000 among males and 94 per 100 000 among females in 1993–1994. The top-ranking cancers among males are lung followed by non-melanoma skin, larynx and bladder. Among females, the order is breast, non-melanoma skin, corpus uteri and ovary[1].

Map. Map showing location of Izmir, Turkey

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The registry contributed data on survival for 12 cancer sites or types for the first time in this volume of the IARC publication on Cancer Survival in Africa, Asia, the Caribbean and Central America.

Data quality indices

The proportion of cases having a histologically verified cancer diagnosis in our series is 95%, varying between 100% for haematopoietic malignancies and 84% for colon cancer. None are registered based on a death certificate only in the series. The exclusion of cases from the survival analysis due to the non-availability of any follow-up information or other reasons was negligible. Thus, 98–100% of the total cases in the series are included in the estimation of the survival probability.

Table 1. Data quality indices - Proportion (%) of histologically verified and death certificate only cases, number and proportion of included and excluded cases by site, Izmir, Turkey, 1995–1997 cases followed-up until 2003

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Outcome of follow-up

The registry collects copies of death certificates mentioning cancer from the provincial health directorate, but because of poor quality and lack of information regarding socio-demographic data and addresses, these data could not be matched with the records of incident cases. Thus, follow-up information on the vital status of all incident cases are collected by one or more of the following ways: repeated scrutiny of records in the respective sources of registration, postal/telephone enquiries and house visits.

The closing date of follow-up was 31st December 2003. The median follow-up ranged between 17 months for myeloid leukaemia and 72 months for breast cancer. The availability of complete follow-up information at five years from the incidence date varied from 79% in rectal cancer to 98% in lymphoid leukaemia. The proportion of losses to follow-up was generally the highest in the extremities of the classified follow-up intervals (within the first year and five or more years of follow-up) for all cancers. This minimizes the bias of estimation of 5-year survival probability, as a sizeable proportion of cases lost to follow-up after five years would have had a complete follow-up until 5 years from the incidence date.

Table 2. Number and proportion of cases with complete / incomplete follow-up and median follow-up (in months) by site, Izmir, Turkey, 1995–1997 cases followed-up until 2003

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Survival statistics

All ages and both sexes together

The top-ranking cancers in terms of 5-year relative survival are breast (77%), larynx (71%), urinary bladder (70%), Hodgkin lymphoma (69%) and cervix (62%). Survival estimates for colon and rectum cancers were 53% and 50%, respectively. The survival figures for haematopoietic malignancies were 51% for lymphoid leukaemia, 32% for myeloid leukaemia and multiple myeloma.

The 5-year age-standardized relative survival (ASRS) estimate for all ages together is generally less than or similar to the corresponding unadjusted one with a few exceptions. Also, the 5-year ASRS (0–74 years of age) is generally higher than or similar to the corresponding ASRS (all ages) for most cancers.

Table 3. Comparison of 1-, 3- and 5-year absolute and relative survival and 5-year age-standardized relative survival (ASRS) by site, Izmir, Turkey, 1995–1997 cases followed-up until 2003

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Figure 1a. Top five cancers (ranked by survival), Izmir, Turkey, 1995–1997

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Sex

Table 4a. Site-wise number of cases, 5-year absolute and relative survival by sex, Izmir, Turkey, 1995–1997 cases followed-up until 2003

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Male

The rank order on the 5-year relative survival reveals breast (76%) at the top, followed by larynx (71%), urinary bladder (69%), Hodgkin lymphoma (68%) and rectum (56%). Survival from rectal cancer is noticeably higher among males than females.

Figure 1b. Top five cancers (ranked by survival), Male, Izmir, Turkey, 1995–1997

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Female

The highest 5-year relative survival was observed in cancer of the breast (77%) followed by larynx (73%), urinary bladder (72%), Hodgkin lymphoma (69%) and cervix (62%). Survival from ovarian cancer is 59%. The survival is markedly higher among females than males in non-Hodgkin lymphoma and myeloid leukaemia.

Figure 1c. Top five cancers (ranked by survival), Female, Izmir, Turkey, 1995–1997

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Age group

The 5-year relative survival by age group portrays an inverse relationship: decreasing survival with increasing age at diagnosis for cancer of the cervix. In the rest, it is observed to be fluctuating.

Table 4b. Site-wise number of cases, 5-year absolute and relative survival by age group, Izmir, Turkey, 1995–1997 cases followed-up until 2003

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Extent of disease

A majority of cases among cancer of the larynx (32%) have been diagnosed with localized disease. In ovarian cancer, the proportion of cases with distant metastasis (47%) is higher than other categories. Regional spread of disease is the commonest among cancers of the colon (44%), rectum (41%), breast (34%) and cervix (42%). The extent of disease was unknown in 23–40%. The 5-year absolute survival by extent of disease reveals no differences in localized, regional and unknown categories for cancer of the rectum; distant metastasis cases among cancer of the larynx fare as well as cases with regional spread of disease. Cases with localized cervix cancer have survival similar to those classified as unknown.

Table 5. Proportion (%) of cases and 5-year absolute survival by extent of disease and site, v

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Figure 2a–2f. Absolute survival from selected cancers by extent of disease: Izmir, Turkey

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Figure 2a. Absolute survival by extent of disease: Izmir, Turkey: Cancer of the colon

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Figure 2b. Absolute survival by extent of disease: Izmir, Turkey: Cancer of the rectum

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Figure 2c. Absolute survival by extent of disease: Izmir, Turkey: Cancer of the larynx

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Figure 2d. Absolute survival by extent of disease: Izmir, Turkey: Cancer of the breast

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Figure 2e. Absolute survival by extent of disease: Izmir, Turkey: Cancer of the cervix

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Figure 2f. Absolute survival by extent of disease: Izmir, Turkey: Cancer of the ovary

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References

  1. Fidaner C, Eser SY, Parkin DM. Incidence in Izmir in 1993–1994: first results from Izmir Cancer Registry. Eur J Cancer. 2001; 37: 83–92.
    (link to pubmed)