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Zimbabwe national cancer registry

The Zimbabwe national cancer registry was established in 1985 as a population-based cancer registry at the Parirenyatwa Hospital, Medical School of the University of Zimbabwe, Harare, under the support of the Ministry of Health and Child Welfare, IARC and other organizations. It contributed data to the quinquennial IARC publication Cancer Incidence in Five Continents in volumes VII (for African (black) and European (white) populations) and VIII (for black population only)^[1]. Cancer is not a notifiable disease, and registration of cases is done by active methods. The principal sources of data are the medical records in the cancer departments, hospitals, pathology laboratories in the public and private sectors and specific clinical research studies. The registry covers the city of Harare and caters to a population of about 1.5 million in 1997 with a sex ratio of 943 females to 1000 males. The average annual age-standardized incidence rate (ASR) of all cancers except non-melanoma skin among the black population was 223 per 100 000 among males and 219 per 100 000 among females in 1993–1997; the corresponding figures for the white population in 1990–1992 were 291 per 100 000 males and 298 per 100 000 females^[1,2,3].

Map. Map showing location of Harare, Zimbabwe Click here to open map (PDF format)

The registry has contributed data on survival from the 17 cancer sites or types in this volume of the IARC publication on Cancer Survival in Africa, Asia, the Caribbean and Central America. For this study, only sub-samples of Harare resident cases among 17 common cancers are included. For most cancers, it was intended that a minimum of 150 cases be randomly selected. For cervix and breast cancers and Kaposi sarcoma, the number intended is 300. For breast cancer, it is equally distributed among minority (white) and African (black) races. For the rest of cancers, the inclusion of the minority races (other than white) is only by chance^[4].

Data quality indices

The proportion of cases with histological confirmation of cancer diagnosis in this series is 65%, varying between 20% for liver cancer and 100% for Hodgkin lymphoma. The proportion of cases registered on a death certificate only is 10%, ranging from nil to 34%. The exclusion of cases without any follow-up information or other inconsistencies ranged from 1–8%. Thus, 58–97% in the series among different cancers 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, Harare, Zimbabwe, 1993–1997 cases* followed-up unitl 1999, all races together Click here to open table (PDF format) Click here to open comparative statistics by registry

Outcome of follow-up

Follow-up has been carried out predominantly by active methods. Cancer mortality information obtained from accessible death certificates in greater Harare is matched with the registry database. The vital status of the unmatched incident cases is then ascertained by repeated scrutiny of hospital records, postal enquiries and house visits.

The closing date of follow-up was 31^st December 1999. The median follow-up varied from 1 month in liver cancer to 54 months for melanoma skin cancer. Complete follow-up at five years from the incidence date ranged from 94% in cancer of the larynx to 100% for many cancers.

Table 2. Number and proportion of cases with complete / incomplete follow-up and median follow-up (in months) by site, Harare, Zimbabwe, 1993–1997 cases* followed-up until 1999, all races together Click here to open table (PDF format) Click here to open comparative statistics by registry

Survival statistics

All ages and both sexes together

The survival estimates for different cancers were tabulated separately for the black, white and all races together.

Black population

The 5-year relative survival estimate was the highest in cancer of the eye (66%). The corresponding figures for melanoma skin and Hodgkin lymphoma are 58% and 51%, respectively. The lowest survival rate was encountered with liver cancer (4%).

	Table 3a. Comparison of 1-, 3- and 5-year absolute and relative survival and 5-year age-standardized relative survival (ASRS) by site, Harare, Zimbabwe, Black, 1993–1997 cases* followed-up until 1999 Click here to open table (PDF format) Click here to open comparative statistics by registry
	Figure 1a. Top five cancers (ranked by survival), Black, Harare, Zimbabwe, 1993–1997 Click here to open figure (PDF format)

White population

The top ranking cancers on 5-year relative survival estimate are melanoma skin (101%), urinary bladder (83%) and breast (79%). There are very few cases in half the number of cancers under study.

	Table 3b. Comparison of 1-, 3- and 5-year absolute and relative survival and 5-year age standardised relative survival (ASRS) by site, Harare, Zimbabwe, White, 1993–1997 cases Click here to open table (PDF format) Click here to open comparative statistics by registry
	Figure 1b. Top five cancers (ranked by survival), White, Harare, Zimbabwe, 1993–1997 Click here to open figure (PDF format)

All races together

For both races together, the 5-year age-standardized relative survival (ASRS) probability for all ages together is either greater than or similar to the corresponding unadjusted one for a majority of cancers. The 5-year ASRS (0–74 years of age) was observed to be either less than or similar to the corresponding ASRS (all ages) for all cancers.

	Table 3c. Comparison of 1-, 3- and 5-year absolute and relative survival and 5-year age standardised relative survival (ASRS) by site, Harare, Zimbabwe, all races, 1993–1997 cases followed-up until 1999 Click here to open table (PDF format) Click here to open comparative statistics by registry
	Figure 1c. Top five cancers (ranked by survival), all races, Harare, Zimbabwe, 1993–1997 Click here to open figure (PDF format)

Black vs. white populations

In most cancers where there was an adequate number of cases, the 5-year relative survival was markedly higher among the non than black populations. However, for colon cancer, a higher survival among black than white populations was found. There is not much of a difference in survival from cancers of the rectum and lung between the two populations.

Figure 1d. Comparison of 5 year relative survival (%), Harare, Zimbabwe, 1993–1997 Click here to open figure (PDF format)

Sex

Table 4a. Site-wise number of cases, 5-year absolute and relative survival by sex, Harare, Zimbabwe, 1993–1997 cases followed-up unitl 1999, all races together Click here to open table (PDF format) Click here to open comparative statistics by registry

Male

The 5-year relative survival was distinctly higher among males than females in cancers of the colon, rectum, larynx, breast and urinary bladder.

Female

The highest 5-year relative survival is observed in melanoma skin (83%) followed by cancers of the eye (74%) and breast (62%). Survival rates from cervix and ovarian cancers were 40% and 37%, respectively. Survival is markedly higher among females than males in cancers of the oesophagus, eye and Hodgkin lymphoma.

Age group

The 5-year relative survival by age group is seen to fluctuate, with no definite pattern or trend.

Table 4b. Site-wise number of cases, 5-year absolute and relative survival by age group, Harare, Zimbabwe, 1993–1997 cases followed-up unitl 1999, all races together Click here to open table (PDF format) Click here to open comparative statistics by registry

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References

1. Parkin DM, Whelan SL, Ferlay J and Storm H. Cancer Incidence in Five Continents, Vol I to VIII: IARC Cancerbase No. 7. IARCPress, Lyon, 2005.
   (link to CI5)


2. Chokunonga E, Levy LM, Bassett MT, Mauchaza BG, Thomas DB, Parkin DM. Cancer incidence in the African population of Harare, Zimbabwe: Second results from the cancer registry 1993–1995. Int J Cancer. 2000; 85: 54–59.
   (link to pubmed)


3. Bassett MT, Levy L, Chokunonga E, Mauchaza B, Ferlay J and Parkin DM. Cancer in the European population of Harare, Zimbabwe, 1990-1992. Int J Cancer. 1995; 63: 24–28.
   (link to pubmed)


4. Gondos A, Chokunonga E, Brenner H, Parkin DM, Sankila R, Borok MZ, Chirenje ZM, Nyakabau AM, Bassett MT. Cancer survival in a southern African urban population. Int J Cancer. 2004 Dec 10;112(5):860–4.
   (link to pubmed)