Chapter 13: Cancer survival in Bhopal, India, 1991-1995

Dikshit R, Kanhere S and Surange S

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Abstract

The Bhopal population-based cancer Registry was established in 1986 under the national cancer registry programme to investigate the after-effect of a gas leak in 1984. Cancer registration is done entirely by active methods. The registry is contributing data on survival for 16 cancer sites or types registered during 1991–1995. Follow-up of cases was done by active methods with median follow-up time ranging between 8–44 months for different cancers. The proportion with histologically verified diagnosis for various cancers ranged between 61–100%; death certificates only (DCOs) comprised 0–2%; 50–92% of total registered cases were included for survival analysis. The 5-year age-standardized relative survival rates for common cancers were mouth (34%), cervix (31%), breast (25%), tongue (12%), oesophagus (3%) and lung (1%). The 5-year relative survival by age group showed that survival was the highest in the younger age group (45 years and below) for a majority of cancers. A decreasing survival with increasing clinical extent of disease was noted for most cancers studied.


Bhopal Cancer Registry

The Bhopal Population-Based Cancer Registry is the only one of its kind in the central part of India. It was established in 1986 as a special purpose registry at the Gandhi Medical College, Bhopal, under the National Cancer Registry Programme, to investigate the after-effect of the gas leak in 1984. Data from the registry have been regularly published by the Indian Council of Medical Research[1]. The method of cancer registration is entirely done by active methods. The registry staff visits the various medical institutions in and around Bhopal city for data collection by direct interview of cases and/or from medical records[2]. The registry covers an area of 285 km2 and caters to an entirely urban population of about 1.4 million in 2001 with a sex ratio of 893 females to 1000 males. The average annual age-standardized incidence rate is 114 per 100 000 among males and 104 per 100 000 among females with a lifetime cumulative risk of one in 10 of developing cancer for both sexes in the period 1999–2001. The leading site of cancer among males is the lung followed by oral cavity and oesophagus. The ranking among females is breast followed by cervix and oral cavity[1].

Map. Map showing location of Bhopal, India

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The registry is contributing data on survival from cancer for the first time in this volume of the IARC publication on Cancer Survival in Africa, Asia, the Caribbean and Central America. Data on survival from 16 cancer sites or types registered during 1991–1995 are reported.

Data quality indices

The proportion of cases with histological confirmation of cancer diagnosis in this series is 84%, from 100% for non-Hodgkin lymphoma and lymphoid leukaemia to 61% for lung cancer. Cases without any follow-up comprised 19%, with a low of 6% (colon cancer) and a high of 48% (non-Hodgkin lymphoma). The exclusion of cases from the survival analysis ranged between 8% and 50%. Thus, 50–92% of the total cases registered 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, Bhopal, India, 1991-1995 cases followed-up until 2000

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Outcome of follow-up

Follow-up has been carried out predominantly by active methods. These included abstraction of cancer mortality information from the hospitals and the vital statistics division records. The abstracted data are first matched with the incident cancer database. The follow-up information for the unmatched incident cases is then obtained through house visits.

The closing date of follow-up was 31st December 2000. The median follow-up (in months) ranged between 8.3 for cancer of the oesophagus and 44.1 for cancer of the cervix. No partial information is available on follow-up within five years from the incidence date. Cases with no follow-up have been excluded; hence, all the reported cases have a complete follow-up at five years from the incidence date.

Table 2. Number and proportion of cases by vital status and median follow-up (in months) by site, Bhopal, India, 1991-1995 cases followed-up until 2000

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Survival statistics

All ages and both sexes together

The 5-year relative survival is the highest in cervix cancer (35%) and the lowest in lung cancer (1%). The survival figures for head and neck cancers are oral cavity (34%), tongue (11%) and hypopharynx (2%). The rank order among the gastrointestinal tract cancers is rectum (9%), colon (7%), oesophagus (4%) and stomach (3%). The survival from non-Hodgkin lymphoma is 11%, lymphoid leukaemia is 3% and myeloid leukaemia is 17%.

The 5-year age-standardized relative survival (ASRS) probability for all ages together was observed to be less than the corresponding unadjusted one barring a few exceptions. The 5-year ASRS (0-74 years of age) was observed to be higher than the corresponding ASRS (all ages) for all cancers.

Table 3. Comparison of 1-, 3- and 5-year absolute and relative survival and 5-year age-standardized relative survival (ASRS) by site, Bhopal, India, 1991-1995 cases followed-up until 2000

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Figure 1a. Top ten cancers (ranked by survival), Bhopal, India, 1991-1995

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Sex

Table 4a. Site-wise number of cases, 5-year absolute and relative survival by sex, Bhopal, India, 1991-1995 cases followed-up until 2000

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Male

The 5-year relative survival was the highest for male-breast cases (75%; 3 cases) followed by oral cavity (35%) and lymphoid leukaemia (16%). Survival from cancer of the urinary bladder and lymphoid leukaemia was noticeably higher among males than females.

Figure 1b. Top five cancers (ranked by survival), Male, Bhopal, India, 1991-1995

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Female

Non-Hodgkin lymphoma (61%; 5 cases) tops the ranking by 5-year relative survival; the others in order are cervix (35%), breast (32%) and oral cavity (32%). Survival was distinctly higher among females than males in non-Hodgkin lymphoma.

Figure 1c. Top five cancers (ranked by survival), Female, Bhopal, India, 1991-1995

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Age group

The 5-year relative survival analysis by age group indicates that no case aged 75 years and above at diagnosis has survived 5 years after diagnosis. The number of cases was also the least in this age group. Survival was the highest in the youngest age group of 45 years and below for a majority of cancers.

Table 4b. Site-wise number of cases, 5-year absolute and relative survival by age group, Bhopal, India, 1991-1995 cases followed-up until 2000

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Extent of disease

A majority of cases with tongue and oral cavity cancers were diagnosed with a regional spread of disease (56%). For cancers of the colon and rectum, most cases presented with a localized disease (38% and 41%). For breast cancer, both localized (43%) and regional (44%) disease constituted equal proportions. Two thirds of ovarian cancers were diagnosed at a localized stage and 70% of cervix cancers had a regional spread. The extent of disease was unknown in 1-17%. The 5-year absolute survival by extent of disease revealed that none of the cases with distant metastasis at diagnosis survived 5 years for any cancer. Breast cancer cases with unknown extent of disease and ovarian cancer cases with regional spread had a higher or same 5-year survival probability as that of a localized disease.

Table 5. Proportion (%) of cases and 5-year absolute survival by extent of disease and site, Bhopal, India, 1991-1995

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Figure 2a-2g. Absolute survival (%) from selected cancers by extent of disease : Bhopal, India

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Figure 2a. Absolute survival (%) by extent of disease : Bhopal, India: Cancer of the tongue

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Figure 2b. Absolute survival (%) by extent of disease : Bhopal, India: Cancer of the oral cavity

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Figure 2c. Absolute survival (%) by extent of disease : Bhopal, India: Cancer of the colon

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Figure 2d. Absolute survival (%) by extent of disease : Bhopal, India: Cancer of the rectum

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Figure 2e. Absolute survival (%) by extent of disease : Bhopal, India: Cancer of the breast

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Figure 2f. Absolute survival (%) by extent of disease : Bhopal, India: Cancer of the cervix

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Figure 2g. Absolute survival (%) by extent of disease : Bhopal, India: Cancer of the ovary

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Acknowledgements

The authors are grateful to all the staff of Bhopal Cancer Registry for their excellent work.


References

  1. National Cancer Registry Programme. Consolidated report of population-based cancer registries: 1999–2001. Indian Council of Medical Research, New Delhi, 2004.

  2. Bhopal Cancer Registry. Incidence of cancer morbidity and mortality in Bhopal Urban Agglomerate: 1995–1999. Gandhi Medical College, Bhopal, 2003.