Chapter 5: Cancer survival in Hong Kong SAR, China, 1996-2001
Law SC and Mang OW
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The registry contributed data on survival from 45 cancer sites or types for the first time in this volume of the IARC publication Cancer survival in Africa, Asia, the Caribbean and Central America.
The closing date of follow-up is 31st December 2003. The median follow-up ranged from 4 months in cancer of the pancreas and unspecified leukaemia to 60 months in lip cancer.
The 5-year age-standardized relative survival (ASRS) probability for all ages together is generally lesser than or similar to the corresponding unadjusted one for most cancers. Also, the 5-year ASRS (0–74 years of age) is generally higher than or similar to the corresponding ASRS (all ages) for a majority of cancers.
Note: The extent of disease of the breast cancer data presented here is a summary of a pilot study carried out retrospectively by the registry in 2003. The project was conducted on a cohort of breast cancer cases diagnosed between 1996 and 2001. Information on about 80% of cases was audited and updated. Follow-up was done passively by matching with the death register. Owing to technical difficulties, we made an assumption that each ever-registered case was alive if not known to be dead. The possibility exists that some patients (especially for distant-staged groups) seek more aggressive treatment outside Hong Kong and are eventually lost to follow-up or die in other regions without making death registration here. This may have inflated survival rates. The much lower proportion of patients with distant tumours may also lead to a higher overall relative survival in this category of extent of disease. Since information is not fully available on the variables influencing survival, this is of particular concern in the above survival comparisons. One should take account of these differences when comparing these results with other findings.
Abstract
The Hong Kong cancer registry was established in 1963 and cancer registration is done by passive and active methods. The registry contributed data on 45 cancer sites or types registered during 1996–2001 for this survival study. Follow-up has been carried out by passive methods with median follow-up ranging from 4–60 months. The proportion of cases with histologically verified cancer diagnosis ranged from 38–100%; death certificates only (DCOs) ranged from 0–11%; 83–99% of total registered cases were included for survival analysis. The 5-year age-standardized relative survival exceeded 100% for lip and non-melanoma skin followed by thyroid (94%) and testicular (92%) cancers. The corresponding survival for common cancers were breast (90%), colon (61%), liver and lung (22%), nasopharynx (70%), rectum (59%) and stomach (39%). The 5-year relative survival by age group showed a decreasing trend with increasing age groups for most cancers. A decreasing survival with increasing clinical extent of disease was noted for breast cancer.Hong Kong cancer registry
The Hong Kong cancer registry was established in 1963, and is currently based at the clinical oncology department, Queen Elizabeth Hospital, Hospital Authority of Hong Kong. The registry has been contributing data to the quinquennial IARC publication Cancer Incidence in Five Continents since Vol IV[1]. Cancer notification is by an administrative order without a specific law. Hence, cancer registration is done by passive and active methods. The principal sources of information on cancer cases are the records in more than 50 institutions comprising the hospitals in public and private sectors, radiation centres and pathology laboratories as well as voluntary notifications from private practitioners. The registry covers the entire country (1104 km2) and a population of about 6.9 million with a sex ratio of 1076 females to 1000 males in 2004. The average annual age-standardized incidence rate is 265 per 100 000 among males and 197 per 100 000 among females, with a lifetime cumulative risk of one in 4 of developing cancer in the period 1998–2002. The top ranking cancers among males are lung followed by liver and colon. Among females, the order is breast, lung and colon[2].| Map: Map showing location of Hong Kong SAR, People's Republic of China Click here to open map (PDF format) |
Data quality indices
The proportion of cases with histologically verified cancer diagnosis in our series is 86%, varying from 38% (cancer of the pancreas) to 100% (melanoma of the skin and kidney, and mesothelioma). The proportion of cases registered as death certificates only (DCOs) is 1%, ranging between 0% for many cancers and 11% for unspecified leukaemia. Cases excluded without any follow-up are negligible. Thus, 83–99% of the total cases registered are included in the estimation of the survival probability (see note on next page). | Table 1. Data quality indices - Proportion (%) of histologically verified and death certificate only cases, number and proportion of included and excluded cases by site, Hong Kong SAR, China, 1996–2001 cases followed-up until 2003 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 by passive methods. This included obtaining cancer mortality information from the death certificates in births, deaths and marriages registry of the government. The mortality data are periodically matched with the incident cancer database. Unmatched incident cases are then presumed to be alive on the last date of the year for which the mortality data is fully available.The closing date of follow-up is 31st December 2003. The median follow-up ranged from 4 months in cancer of the pancreas and unspecified leukaemia to 60 months in lip cancer.
 | Table 2. Number and proportion of cases by vital status and median follow-up (in months) by site, Hong Kong SAR, China, 1996–2001 cases followed-up until 2003 Click here to open table (PDF format) Click here to open comparative statistics by registry |
Survival statistics
All ages and both sexes together
The 5-year relative survival is the highest in non-melanoma skin and lip cancers (102%) followed by thyroid (94%), testis (90%) and breast (90%). The lowest survival is encountered with pancreatic cancer (17%) preceded by lung (21%), liver and gallbladder (22%) and unspecified leukaemia (25%). Salivary gland (83%) and nasopharynx (75%) among other head and neck cancers and colon and rectum (61%) among gastrointestinal cancers have higher survival rates than others. Survival from cancers of the urinary system is 76% for urinary bladder and 66% for kidney. Hodgkin lymphoma had a better survival (84%) than non-Hodgkin lymphoma (56%). The survival figures for leukaemias are lymphoid (60%) and myeloid (34%).The 5-year age-standardized relative survival (ASRS) probability for all ages together is generally lesser than or similar to the corresponding unadjusted one for most cancers. Also, the 5-year ASRS (0–74 years of age) is generally higher than or similar to the corresponding ASRS (all ages) for a majority of cancers.
 | Table 3. Comparison of 1-, 3- and 5-year absolute and relative survival and 5-year age-standardized relative survival (ASRS) by site, Hong Kong SAR, China, 1996–2001 cases followed-up until 2003 Click here to open table (PDF format) Click here to open comparative statistics by registry |
 | Figure 1a. Top ten cancers (ranked by survival), Hong Kong SAR, China, 1996–2001 Click here to open figure (PDF format) Click here to open graph for all the cancer sites |
Sex
 | Table 4a. Site-wise number of cases, 5-year absolute and relative survival by sex, Hong Kong SAR, China, 1996–2001 cases followed-up until 2003 Click here to open table (PDF format) Click here to open comparative statistics by registry |
Male
The top five cancers ranked on the 5-year relative survival probabilities are lip (102%), non-melanoma skin (101%), breast (100%), testis and thyroid (90%). Survival from breast cancer is noticeably higher among males than females. | Figure 1b. Top five cancers (ranked by survival), Male, Hong Kong SAR, China, 1996–2001 Click here to open figure (PDF format) Click here to open graph for all the cancer sites |
Female
The highest 5-year relative survival probability is observed for non-melanoma skin cancer (104%), followed by lip (102%), thyroid (95%), Hodgkin lymphoma (92%) and salivary gland (90%). The survival is distinctly higher among females than males in most of the head and neck cancers, oesophagus, nose and sinuses, mesothelioma, adrenal glands, Hodgkin lymphoma and unspecified leukaemia. | Figure 1c. Top five cancers (ranked by survival), Female, Hong Kong SAR, China, 1996–2001 Click here to open figure (PDF format) Click here to open graph for all the cancer sites |
Age group
The 5-year relative survival by age group reveals an inverse relationship: a decreasing survival with increasing age at diagnosis for cancers of the oral cavity, nasopharynx, liver, nose and sinuses, lung, melanoma skin, soft tissue, cervix, ovary, bladder, thyroid, non-Hodgkin lymphoma and myeloid leukaemia. In the rest, it is observed to be fluctuating. | Table 4b. Site-wise number of cases and 5-year relative survival by age group, Hong Kong SAR, China, 1996–2001 cases followed-up until 2003 Click here to open table (PDF format) Click here to open comparative statistics by registry |
Extent of disease
A high proportion of cases of cancer breast is classified under the regional category of extent of disease (35%) followed by 12% in localized and 1% in distant metastasis categories. However, the extent of disease is unknown in 52%. The 5-year absolute survival by extent of disease followed the expected pattern: highest for localized cases followed by regional and distant metastasis cases among known categories of extent of disease. It is 83% for unknown category. | Table 5. Proportion (%) of cases and 5-year absolute survival by extent of disease of breast cancer, Hong Kong SAR, China, 1996–2001 Click here to open table (PDF format) Click here to open comparative statistics by registry |
 | Figure 2. Absolute survival by extent of disease: Hong Kong SAR, China, 1996–2001, cancer of the breast Click here to open figure (PDF format) Click here to open comparative statistics by cancer site |
Note: The extent of disease of the breast cancer data presented here is a summary of a pilot study carried out retrospectively by the registry in 2003. The project was conducted on a cohort of breast cancer cases diagnosed between 1996 and 2001. Information on about 80% of cases was audited and updated. Follow-up was done passively by matching with the death register. Owing to technical difficulties, we made an assumption that each ever-registered case was alive if not known to be dead. The possibility exists that some patients (especially for distant-staged groups) seek more aggressive treatment outside Hong Kong and are eventually lost to follow-up or die in other regions without making death registration here. This may have inflated survival rates. The much lower proportion of patients with distant tumours may also lead to a higher overall relative survival in this category of extent of disease. Since information is not fully available on the variables influencing survival, this is of particular concern in the above survival comparisons. One should take account of these differences when comparing these results with other findings.
References
- 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) - Curado MP, Edwards B, Shin HR, Storm H, Ferlay J, Heanue M and Boyle P. Cancer Incidence in Five Continents, Vol. IX: IARC Scientific Publications No. 160. IARCPress, Lyon, 2007.
(link to CI5)