A model approach to calculate cancer prevalence from 5 years survival data for selected cancer sites in India--part II.

OBJECTIVE: Prevalence is a statistic of primary interest in public health. In the absence of good follow-up facilities, it is often difficult to assess the complete prevalence of cancer for a given registry area. An attempt is made to arrive at the complete prevalence including limited duration prevalence with respect of selected sites of cancer for India by fitting appropriate models to 1, 3 and 5 year cancer survival data available for selected registries of India. METHODOLOGY: Cancer survival data, available for the registries of Bhopal, Chennai, Karunagappally, and Mumbai was pooled to generate survival for the selected cancer sites. With the available data on survival for 1, 3 and 5 years, a model was fitted and the survival curve was extended beyond 5 years (up to 30 years) for each of the selected sites. This helped in generation of survival proportions by single year and thereby survival of cancer cases. With the help of estimated survived cases available year wise and the incidence, the prevalence figures were arrived for selected cancer sites and for selected periods. In our previous paper, we have dealt with the cancer sites of breast, cervix, ovary, lung, stomach and mouth (Takiar and Jayant, 2013). RESULTS: The prevalence to incidence ratio (PI ratio) was calculated for 30 years duration for all the selected cancer sites using the model approach showing that from the knowledge of incidence and P/I ratio, the prevalence can be calculated. The validity of the approach was shown in our previous paper (Takiar and Jayant, 2013). The P/I ratios for the cancer sites of lip, tongue, oral cavity, hypopharynx, oesophagus, larynx, nhl, colon, prostate, lymphoid leukemia, myeloid leukemia were observed to be 10.26, 4.15, 5.89, 2.81, 1.87, 5.43, 5.48, 5.24, 4.61, 3.42 and 2.65, respectively. CONCLUSION: Cancer prevalence can be readily estimated with use of survival and incidence data.

Additive properties of crude, age specific and age adjusted rates for cancer incidence and mortality.

BACKGROUND: In National Cancer Registry Programme (NCRP) reports, various rates are routinely provided for 50 cancer sites of males and 54 cancer sites of females. Very often, depending on our interest, we wish to see these rates for group of cancers like head and neck cancers, oral cancers, and reproductive cancers. In such a situation, the desired rates are calculated independently from the actual data and reported. The question is can we derive the rates for groups of cancers from the published reports when the data is provided only for the individual sites? OBJECTIVE: In the present paper, an attempt is made to explore the mathematical properties of various rates to derive them directly for the group of cancer sites from the published data when the rates are provided only for the individual sites. SOURCE OF DATA: The cancer incidence data collected by two urban Population Based Cancer Registries (PBCRs), under the network of NCRP for the period of 2006-08 was considered for the study purposes. The Registries included were: Bangalore and Bhopal. RESULTS: In the present communication, we have shown that the crude rate (CR), age specific rates and age-adjuste rates (AAR) all possess additive properties. This means, given the above rates for individual sites, the above rates can be calculated for groups of sites by simply adding them. In terms of formula it can be stated that CR(Site1+Site2+++ SiteN) = CR(Site1)+CR(Site2) +++ CR(SiteN). This formula holds good for age specific rates as well as for AAR. This property facilitates the calculation of various rates for defined groups of cancers by simply adding the above rates for individual sites from which they are made up.

Pattern of reproductive cancers in India.

BACKGROUND: Reproductive cancers are those that affect the human organs that are involved in producing offspring. An attempt is made in the present communication to assess the magnitude and pattern of reproductive cancers, including their treatment modalities, in India. The cancer incidence data related to reproductive cancers collected by five population-based urban registries, namely Bangalore, Bhopal, Chennai, Delhi and Mumbai, for the years 2006-08 were utilized. The reproductive cancers among females constituted around 25% of the total and around 9% among males. Among females, the three major contributors were cervix (55.5%), ovary (26.1%) and corpus uteri (12.4%). Similarly among males, the three major contributors were prostate (77.6%), penis (11.6%) and testis (10.5%). For females, the AAR of reproductive cancers varied between 30.5 in the registry of Mumbai to 37.3 in the registry of Delhi. In males, it ranged between 6.5 in the registry of Bhopal to 14.7 in the registry of Delhi. For both males and females, the individual reproductive cancer sites showed increasing trends with age. The leading treatment provided was: radio-therapy in combination with chemo-therapy for cancers of cervix (48.3%) and vagina (43.9%); surgery in combination with chemo-therapy (54.9%) for ovarian cancer; and surgery in combination with radio-therapy for the cancers of the corpus uteri (39.8%). In males, the leading treatment provided was hormone-therapy for prostate cancer (39.6%), surgery for penile cancer (81.3%) and surgery in combination with chemo-therapy for cancer of the testis (57.6%).

A model approach to calculate cancer prevalence from 5 year survival data for selected cancer sites in India.

BACKGROUND: Prevalence is a statistic of primary interest in public health. In the absence of good follow- up facilities, it is difficult to assess the complete prevalence of cancer for a given registry area. OBJECTIVE: An attempt was here made to arrive at complete prevalence including limited duration prevalence with respect to selected sites of cancer for India by fitting appropriate models to 1, 3 and 5 years cancer survival data available for selected population-based registries. MATERIALS AND METHODS: Survival data, available for the registries of Bhopal, Chennai, Karunagappally, and Mumbai was pooled to generate survival for breast, cervix, ovary, lung, stomach and mouth cancers. With the available data on survival for 1, 3 and 5 years, a model was fitted and the survival curve was extended beyond 5 years (up to 35 years) for each of the selected sites. This helped in generation of survival proportions by single year and thereby survival of cancer cases. With the help of survival proportions available year-wise and the incidence, prevalence figures were arrived for selected cancer sites and for selected periods. RESULTS: The prevalence to incidence ratio (PI ratio) stabilized after a certain duration for all the cancer sites showing that from the knowledge of incidence, the prevalence can be calculated. The stabilized P/I ratios for the cancer sites of breast, cervix, ovary, stomach, lung, mouth and for life time was observed to be 4.90, 5.33, 2.75, 1.40, 1.37, 4.04 and 3.42 respectively. CONCLUSIONS: The validity of the model approach to calculate prevalence could be demonstrated with the help of survival data of Barshi registry for cervix cancer, available for the period 1988-2006.

An alternative approach to study the changes in the cancer pattern of men in India (1988-2005).

BACKGROUND: Changes in cancer pattern are often studied with regard to rank of leading sites, variation in age adjusted rates of sites over the time or with the help of time trends. However, these methods do not quantify the changes in relation to overall changes that occurred in the total cancer cases over the period of time. An alternative approach is therefore necessary, particularly to identify emerging new cancers. METHODS: The cancer incidence data of various sites for men, over the periods 1988-90 and 2003-05 in India, for five urban registries namely Bangalore, Bhopal, Chennai, Delhi and Mumbai, functioning under the network of National Cancer Registry Programme (ICMR), formed the sources of data for the present analysis. Changes in incidence cases by various cancer sites for men are assessed by calculating the differences in incidence cases over the two period of time. Based on the contribution of each site to total change, the ten most leading sites are identified separately for each registry. The relative changes in the sites with time are taken to identify the most emerging new cancer cases over the period of time. RESULTS: The pooled cancer cases for men among five urban registries increased from 30042 cases in 1988-90 to 46946 cases in 2003-05 registering an increase of about 55.8%. The lowest percentage of increase is observed in the registry of Mumbai (25.6%) and the maximum in Bhopal (96.4%). Based on the pooled figures of five urban registries, the lung cancer contributed the maximum % change (9.7%), followed by cancer of prostate (9.2%), mouth (7.5%), tongue (5.9%) and NHL (5.9%). Based on the pooled figures and the relative changes, the emerging new cancers are prostate (140%), liver (112%) and mouth (95%). The % change by sites and the emerging new cancers varied between the registries.

Projections of number of cancer cases in India (2010-2020) by cancer groups.

INTRODUCTION: Recently, NCRP (ICMR), Bangalore, has published a report on Time Trends in Cancer Incidence Rates. The report also provided projected numbers of cancer cases at the India country level for selected leadingsites. OBJECTIVE: In the present paper, an attempt has been made to project cancer cases for India by sex, years and cancer groups. SOURCES OF DATA: The incidence data generated by population-based cancer registries (PBCRs) at Bangalore, Barshi, Bhopal, Chennai, Delhi and Mumbai for the years 2001-2005 formed the sources of data. In addition, the latest incidence data of North Eastern Registries for the year 2005-06 were utilized. METHODS: The crude incidence rate (CR) was considered suitable for assessing the future load of cancer cases in the country. The Linear Regression method (IARC 1991) was used to assess the time trend and the projection of rates for the periods 2010-2020. For whichever sites where trends were not found to be significant, their latest rates were taken into consideration and assumed to remain same for the period 2010-2020. RESULTS: The total cancer cases are likely to go up from 979,786 cases in the year 2010 to 1,148,757 cases in the year 2020. The tobacco-related cancers for males are estimated to go up from 190,244 in the year 2010 to 225,241 in the year 2020. Similarly, the female cases will go up from 75,289 in year 2010 to 93,563 in the year 2020. For the year 2010, the number of cancer cases related to digestive system, for both males and females, are estimated to be 107,030 and 86,606 respectively. For, head and neck cancers, the estimates are 122,643 and 53,148 cases, respectively. and for the lymphoid and hematopoietic system (LHS), for the year 2010, are 62,648 for males and 41,591 for females. Gynecological-related cancers are estimated to go up from 153,850 in 2010 to 182,602 in 2020. Among males and females, cancer of breast alone is expected to cross the figure of 100,000 by the year 2020.

An alternative approach to study the changes in the cancer pattern of women in India (1988-2005).

BACKGROUND: The changes in the cancer pattern are often studied with the help of changes in the rank of leading sites, changes in the Age Adjusted Rates of the sites over the time or with the help of time trends. However, these methods do not quantify the changes in relation to overall changes that occurred in the total cancer cases over the period of time. An alternative approach was therefore used to assess the changes in cancer pattern in relation to overall changes in time and also an attempt was made to identify the most emerging new cancers in India. METHODS: The cancer incidence data of various sites for women, over the periods 1988-90 and 2003-05 in India, for five urban registries namely Bangalore, Bhopal, Chennai, Delhi and Mumbai, functioning under the network of National Cancer Registry Programme (ICMR), formed the sources of data for the present analysis. The changes in incidence cases by various cancer sites for women were assessed by calculating the differences in incidence cases over the two period of time. Based on the contribution of each site to total change, the ten most leading sites were identified separately for each registry. The relative changes in the sites with time were taken to identify the most emerging new cancer cases over the period of time. RESULTS: The pooled cancer cases for women among five urban registries increased from 29447 cases in 1988-90 to 48472 cases in 2003-05 registering an increased of about 63.3%. The lowest percentage of increase was observed in the registry of Chennai (41.5%) and the maximum in Bhopal (102.0%). Based on the pooled figures, the breast cancer contributed to the maximum % change (38%), followed by ovarian (8.0%), gallbladder (5.1%), corpus uteri (4.9%) and cervix uteri (4.1%). Based on the pooled data and relative changes, the emerging new cancers were corpus uteri (187%), gallbladder (162.1%) and lung cancer (136.1%). The % change by sites and the emerging new cancers varied between the registries.

Problem of small numbers in reporting of cancer incidence and mortality rates in Indian cancer registries.

The present paper examines the problem of small numbers (<20 cases) associated with many sites of cancers in Indian cancer registries. The cancer incidence data of 14 Population Based Cancer Registries for the periods of 2001-03 and 2004-05 were utilized for the analysis. Nine out of 14 registries had more than 50% of their sites being associated with small numbers while seven registries had 50% of their sites having as low as 5 cases. Sites associated with small numbers showed a lot of variation and significant differences in their incidence rates within two years duration which are not feasible. The percentage age distribution was also found to vary with different periods. The paper has effectively shown the effect of population size on incidence rates. For a registry of population size 300,000, the incidence rate of 6 can very well be unstable. There are many registries in the world with their population size less than 200,000. Even in the case of registries with high population (>or= 500,000) the practice is to report the cancer incidence by different ethnic groups with populations less than 200,000 and thereby introduce the problem of small numbers in reporting the incidences of various cancer sites. To overcome this problem, pooling of data over broad age groups or ten years age groups or 3 to 5 years periods is one immediate solution.

Cancer incidence rates and the problem of denominators - a new approach in Indian cancer registries.

In India, the national census provides population figures once every 10 years. However, since cancer incidence data provide various rates for five year age groups, the calculation of the relevant population estimates for a given year between any two-census years, serving as denominators, assumes importance. The Individual Exponential Growth Rate Method is in current use by various Indian cancer registries to estimate the population by five yearly age groups. Using the five yearly age group estimates by the same method, various rates like the Crude rate, Age Standardized Rate and Cumulative Rates, are reported in Cancer Incidence in Five Continents, Vol. VIII. However, this approach has been shown to suffer from bias and often results in sacrificing the overall growth rate and corrections become necessary in five yearly age group populations to maintain it. We here show that the proposed Difference Distribution Method is able to maintain both negative as well as positive growth in different five yearly age group populations. For population projections, this method scores over the Individual Exponential Growth Method, serving as a new methodology for population estimation by five yearly age groups for inter-census years for Indian cancer registries.

An indirect study of cancer survival in the context of developing countries.

With classical approaches, survival refers to the life of a person after diagnosis of disease, and survival studies deal with measurement of the same to evaluate overall performance of a group of patients in terms of quality and quantity of life after diagnosis/treatment. There are numerous difficulties in the conduct of a population-based survival study in the context of developing countries, including India. Loss to follow-up is a typical problem encountered, causing biased estimates. In view of this difficulty with the classical approach, the objective of this study was to propose an indirect methodology for the study of survival. The proposed methodology is based on life table techniques and uses current data on incidence and mortality from the disease. It involves the estimation of person years free of disease (PYFD), person years with disease (PYWD), person years of life lost (PYLL) and average duration of disease (ADD) and their comparison over a time period. Empirical application was carried out for mouth and lung cancers in males and cancers of breast and cervix in females as well as for all sites combined together in each sex. Cancer incidence and mortality data by age and sex for the years 1989, 1993, 1997 and 2001 were obtained from published reports of Mumbai Cancer Registry, India. All causes of deaths for these years were obtained from Mumbai Municipal Corporation. Three life tables were constructed by applying various attrition factors: (a) risk of death from all causes; (b) risk of incidence and that of death from other causes; and (c) risk of death from other causes only. The expectation of life from the second life table gave PYFD. PYWD and PYLL were calculated by suitable subtractions among three expectations of life. ADD was calculated by dividing person years lived with disease by number developing the disease. It was noted that during 1993-2001, PYFD for all sites increased from 59.4 to 62.1 and from 63.8 to 66 years in males and females respectively. PYLL was about 0.8 year in males and 1 year in females. Similarly, PYWD was 0.6 and 1 year in males and females. ADD for all sites varied from 4 to 4.7 years in both sexes. It was about 6 years for mouth cancers and 2 years for lung cancers in males and 4-5 years for breast and cervical cancers in females. Validation of the ADD was carried out by comparison with published data for calculating median duration of disease. Given the difficulties in conduct of classical survival studies, the proposed method may provide a useful tool for having a regular audit of prognostic factors in the community.

Time trend in breast and cervix cancer of women in India - (1990-2003).

The Indian Council of Medical Research (ICMR) started a National Cancer Registry Programme (NCRP) in the year 1982 with the main objective of generating reliable data on the magnitude and pattern of cancer in India. There are about 20 Population Based Cancer Registries (PBCR) which are currently functioning under the network of NCRP. The present paper aims to provide the time trends in the incidence of breast and cervix cancer among females of India. The incidence data collected by Bangalore, Barshi, Bhopal, Chennai, Delhi and Mumbai over the period 1990 to 2003 formed the sources of data. In the year 1990, cervix was the leading site of cancer followed by breast cancer in the registries of Bangalore (23.0% vs 15.9%), Bhopal (23.2% vs 21.4%), Chennai (28.9% vs 17.7%) and Delhi (21.6% vs 20.3%), while in Mumbai breast was the leading site of cancer (24.1% vs 16.0%). By the years 2000-3, the scenario had changed and breast had overtaken as the leading site of cancer in all the registries except in Barshi (16.9% vs 36.8%). The time trend analysis for these sites suggested a significant decreasing trend in the case of cervix in Bangalore and Delhi registries, while the registries of Bhopal, Chennai and Mumbai did not show any significant changes. However, in the case of breast cancer, a significant increasing trend was observed in Bhopal, Chennai and Delhi registries with Bangalore and Mumbai registries demonstrating no such significant changes. Histopathologic confirmation for both malignancies was found to be more than 80% in these registries. It is concluded that in India the cervix cancer rates are decreasing while breast cancer is on the increase.

Early biochemical alterations in manganese toxicity: ameliorating effects of magnesium nitrate and vitamins.

Manganese-induced early biochemical changes and effects of supplementation of magnesium nitrate (Mg(NO3)2) and antioxidant vitamins (A, C, D and E) were studied in rats intoxicated with manganese. Significant elevation in the level of chlorides in plasma, erythrocytes, liver and cerebellum, and a decrease in plasma inorganic phosphate (pi) with an increase in liver pi were observed in animals exposed to manganese as compared to controls. The level of erythrocyte-acid labile phosphate (ALP), nicotinamide adeninedinucleotide (NAD+) and plasma sialic acid (N-acetylneuraminic acid, NANA) also increased significantly. Elevated levels of chlorides in plasma, erythrocytes and cerebellum reversed to normal control values whereas liver chlorides restored partially by the supplementation of Mg(NO3)2. Vitamins supplementation was effective to reverse chlorides level in erythrocytes, liver and cerebellum. Decreased level of pi in plasma and the highly elevated level of erythrocyte ALP were also recovered in animals received Mg(NO3)2 in addition to MnSO4. However, such effect of Mg(NO3)2 was not seen in lowering the elevated level of NANA that restored by the administration of vitamins. Thus, the early alterations in plasma levels of chlorides, pi, and NANA and erythrocyte-ALP seem to be an indicative of early manganese toxicity while Mg(NO3)2 and vitamins supplementation appear to provide, at least in part, protection against manganese toxicity.