Cancer incidence in Karachi, Pakistan: first results from Karachi Cancer Registry

No cancer incidence data from Pakistan have been published in the 5 decades since independence. Incidence data for the period 1995-1997 from the population of the Karachi South district (1.7 million) are presented here. A total of 4,268 new cancer cases were registered during this period: 2,160 cases in males and 2,108 cases in females. Overall, 95.3% of the incident cases were microscopically verified. The incidence rates for all cancers combined were 80.5 per 100,000 (crude) and 136.7 per 100,000 (age- standardised rates [ASR]) for males and 91.8 (crude) and 163.2 per 100,000 (ASR) for females. In males, lung cancer (ASR 20.3) was the most frequently recorded malignancy followed by oral cavity (ASR 13.8) and larynx cancer (ASR 8.6). In females, breast was the most common site of cancer, accounting for one third of female cancers (ASR 51.7), followed by oral cavity (ASR 14.1) and ovarian cancer (ASR 10.2). Karachi reports the highest incidence of breast cancer for any Asian population, except Jews in Israel. Tobacco smoking is estimated to be responsible for 40% of cancers in males and tobacco chewing for a further substantial proportion of head and neck cancers.

Trends in survival rates of cancer in Cuba

Reports of population-based survival rates of cancer from developing countries are infrequent. In Latin America, only the Cancer Registry of Puerto Rico has published population-based survival data. The National Cancer Registry of Cuba has achieved three survival studies with cases incident in 1976, 1982 and 1988-1989. This article deals with the global observed and relative survival rates estimated in the latter study. Survival time trends are analysed. In the period 1988-1989, 12,985 primary cancer cases were included from the most common cancer sites, with the exclusion of cancer in situ cases and 8900 cases reported by 'death certificate only' (DCO) (35.8%). The vital status of cases was checked up to 31 December 1994 using a mixed follow-up system with the exclusion of 2900 cases lost to follow-up (11.2%). DCO proportions are shown for the major sites and compared to those of 1982. Observed survival rates were estimated by Kaplan-Meier method using the SPSS Statistical Software. The relative rates were estimated by the Hakulinen's Computer Program Package for Cancer Survival Studies (1988) using life tables from Cuban population. Statistical comparisons of survival curves by year of diagnosis were achieved by using the Log-Rank and Pearson statistic tests. Global results are shown by year of follow-up and a comparative analysis is done in time and with internationals values. Survival rates decreased in the period 1982/1988-1989 for colon, prostate and lung cancer. Prostate cancer shows a low five years relative survival rate when compared with the USA, but its observed rate is comparable with Puerto Rico's. Figures for mouth and lung cancer were comparable with the corresponding figures of the USA and Europe. Breast and cervix cancers rates are comparable with the European mean and the blacks in USA.

The structure of threonyl-tRNA synthetase-tRNA(Thr) complex enlightens its repressor activity and reveals an essential zinc ion in the active site

E. coli threonyl-tRNA synthetase (ThrRS) is a class II enzyme that represses the translation of its own mRNA. We report the crystal structure at 2.9 A resolution of the complex between tRNA(Thr) and ThrRS, whose structural features reveal novel strategies for providing specificity in tRNA selection. These include an amino-terminal domain containing a novel protein fold that makes minor groove contacts with the tRNA acceptor stem. The enzyme induces a large deformation of the anticodon loop, resulting in an interaction between two adjacent anticodon bases, which accounts for their prominent role in tRNA identity and translational regulation. A zinc ion found in the active site is implicated in amino acid recognition/discrimination.

Visual inspection of the uterine cervix after the application of acetic acid in the detection of cervical carcinoma and its precursors

BACKGROUND

Organized cervical cytology screening programs are not feasible in many developing countries where cervical carcinoma is an important cause of mortality among adult women. This study compared visual inspection of the cervix after application of 3-4% acetic acid (VIA, or cervicoscopy) with cytology as methods for the detection of cervical carcinoma and its precursors.

METHODS

Three thousand women were examined by both VIA and cytology. Those positive on one or both of the screening tests (n = 423) or those who had clinically suspicious lesions even if the tests were negative (n = 215) were invited for colposcopy. Directed biopsies were obtained from 277 of 573 women at colposcopy. Those with moderate dysplasia or worse lesions diagnosed by histology were considered true-positives. Those with no lesions or with reactive or reparative changes at colposcopy and those for whom histology revealed no pathology, reactive or reparative changes, atypia, or mild dysplasia were considered false-positives. The detection rate of true-positive cases and the approximate specificity of the two tests were compared.

RESULTS

VIA was positive in 298 women (9.8%), and cytology was positive (for atypia or worse lesions) in 307 women (10.2%). Of the 51 true-positive cases (20 cases of moderate dysplasia, 7 of severe dysplasia, 12 of carcinoma in situ, and 12 of invasive carcinoma), VIA detected 46 (90.1%) and cytology 44 (86.2%), yielding a sensitivity ratio of 1.05. VIA detected five lesions missed by cytology, and cytology detected three missed by VIA; both missed two lesions. The approximate specificities were 92.2% for VIA and 91.3% for cytology. The positive predictive value of VIA was 17.0%, and that of cytology was 17.2%.

CONCLUSIONS

These results indicate that VIA and cytology had very similar performance in detecting moderate dysplasia or more severe lesions in this study. VIA merits further evaluation as a primary screening test in low-resource settings.

Head and neck cancer: a global perspective on epidemiology and prognosis

Head and neck cancers (ICD-9 categories 140-149 and 161) are common in several regions of the world where tobacco use and alcohol consumption is high. The age standardized incidence rate of head and neck cancer (around 1990) in males exceeds 30/100, 000 in regions of France, Hong Kong, the Indian sub-continent, Central and Eastern Europe, Spain, Italy, Brazil, and among US blacks. High rates (> 10/100,000) in females are found in the Indian sub-continent, Hong Kong and Philippines. The highest incidence rate reported in males is 63.58 (France, Bas-Rhin) and in females 15.97 (India, Madras). The variation in incidence of cancers by subsite of head and neck is mostly related to the relative distribution of major risk factors such as tobacco or betel quid chewing, cigarette or bidi smoking, and alcohol consumption. Some degree of misclassification by subsites is a clear possibility in view of the close proximity of the anatomical subsites. While mouth and tongue cancers are more common in the Indian sub-continent, nasopharyngeal cancer is more common in Hong Kong; pharyngeal and/or laryngeal cancers are more common in other populations. While the overall incidence rates show a declining trend in both sexes in India, Hong Kong, Brazil and US whites, an increasing trend is observed in most other populations, particularly in Central and Eastern Europe, Scandinavia, Canada, Japan and Australia. The overall trends are a reflection of underlying trends in cancers of major subsites which seem to be related to the changing prevalence of risk factors. The five year relative survival varies from 20-90% depending upon the subsite of origin and the clinical extent of disease. While primary prevention is the potential strategy for long term disease control, early detection and treatment may have limited potential to improve mortality in the short term.

[Population-based cancer survival: an analysis of 16,922 cases]

OBJECTIVE

In the period of 1982-1991, 16,922 patients with cancers from 15 sites of Qidong population-based cancer registry were analysed for evaluation of cancer survival as well as different cancer control measures.

METHODS

Observed survival rate (OS) was computed by the Kaplan-Meier method using EGRET statistical software package. Relative survival (RS) which is the ratio of the OS to the expected rate was calculated by using Qidong life table with respect to sex, age and calendar period of observation.

RESULTS

The five-year OS for the 5 leading sites of cancers, liver, stomach, lung, oesophagus, and rectum were 1.8%, 11.6%, 3.0%, 3.3%, and 19.9%, respectively. The five-year RS for the 5 sites were 1.9%, 14.0%, 3.6%, 4.2%, and 23.7%, respectively, in which, 1.7%, 14.8%, 3.4%, 4.2%, and 26.0% for males, and 2.7%, 12.7%, 4.1%, 4.0%, and 22.0% for females, respectively. Female patients with breast cancer and cervix cancer had 5-year RS of 54.6% and 33.0%.

CONCLUSION

Cancer survival rates for all sites are poor, in which that of the liver is the lowest, while that of the breast, the highest. The survivals of cancers for all sites, especially for breast, cervix, and leukaemia are seen to be lower than those of European countries except for oesophagus, pancreas and lung cancer which do not achieve improved survival both in developing and developed countries. There will be a long way to improve the total cancer survival, as well as the cancer treatment in the developing countries.

Carbohydrate specificity and quaternary association in basic winged bean lectin: X-ray analysis of the lectin at 2.5 A resolution

The structure of basic Winged Bean Agglutinin (WBAI) with two dimeric molecules complexed with methyl-alpha-D-galactopyranoside in the asymmetric unit, has been determined by the molecular replacement method and refined with 2.5 A X-ray intensity data. The polypeptide chain of each monomer has the characteristic legume lectin tertiary fold. The structure clearly defines the lectin-carbohydrate interactions. It reveals how the unusually long variable loop in the binding region endows the lectin with its characteristic sugar specificity. The lectin forms non-canonical dimers of the type found in Erythrina corallodendron lectin (EcorL) even though glycosylation, unlike in EcorL, does not prevent the formation of canonical dimers. The structure thus further demonstrates that the mode of dimerisation of legume lectins is not necessarily determined by the covalently bound carbohydrate but is governed by features intrinsic to the protein. The present analysis and our earlier work on peanut lectin (PNA), show that legume lectins are a family of proteins in which small alterations in essentially the same tertiary structure lead to wide variations in quaternary association. A relationship among the non-canonical modes of dimeric association in legume lectins is presented.

Chemoprevention of oral leukoplakia with vitamin A and beta carotene: an assessment

We conducted a double-blind placebo-controlled trial to evaluate the chemopreventive potential of either vitamin A alone or beta carotene alone in subjects with oral leukoplakia in Kerala, India. We randomised 160 fishermen and women with oral precancerous lesions to receive oral vitamin A (retinyl acetate 300,000 IU/week x 12 months, n = 50), or beta carotene (360 mg/week x 12 months, n = 55), or placebo (n = 55). Blood, saliva and urine samples were collected at baseline and at exit to study serum micronutrients and mutagenicity assays. Biopsies of the mucosal lesions at entry were performed for histopathological exclusion of malignancy. The subjects were examined once every 2 months to establish clinical response of lesions and toxicity, if any. The results are based on 43 complaint subjects on placebo, 42 on vitamin A and 46 on beta carotene. The complete regression rates were: 10% in the placebo arm, 52% with vitamin A and 33% with beta carotene (P < 0.0001). Homogeneous leukoplakias and smaller lesions responded better than non-homogeneous and larger lesions. No major toxicities were observed. Half of the responders with beta carotene and two thirds with vitamin A relapsed after stopping supplementation. Serum beta carotene concentration increased substantially with beta carotene administration while with vitamin A supplementation there was no change in serum retinol levels. In the vitamin A treated group there was a significant decrease in serum alpha tocopherol. Vitamin A administration resulted in a significant remission of oral leukoplakia without any side effects of prolonged vitamin A supplementation. The results of this study, as well as those from previous studies, appear to provide strong supporting evidence to justify long term trials with vitamin A in subjects with high-risk leukoplakias with oral cancer as an endpoint.

Health care auxiliaries in the detection and prevention of oral cancer

Oral cancer is one among the few human cancers with a vast potential for prevention. One of the operational strategies considered to translate preventive measures into practice in developing countries has been the use of community health workers and other health auxiliaries of the primary health care system to disseminate anti-tobacco health education messages and to provide mouth examinations in high-risk individuals during their routine home visits and community meetings. Studies conducted in India and Sri Lanka to address the role of the above approach indicate that it is feasible to train community health workers and other health auxiliaries in primary prevention and early detection of oral cancer and precancerous lesions. However, no evidence of the efficacy of such an approach in reducing the incidence and mortality from oral cancer is yet available. Sufficient evidence in terms of efficacy and cost effectiveness is needed to justifiably convince health administrators for the inclusion of non-communicable disease control in general and oral cancer screening in particular as part of the primary health care delivery by community health workers and other health auxiliaries especially when considering the burden of already existing work responsibilities. The need for studies in this direction is very obvious. However, the opportunities for 'case-finding' and health education should be utilised when encountering high-risk subjects both in primary medical and health care.

Radiotherapy in the treatment of verrucous carcinoma of the oral cavity

Verrucous carcinomas are considered to have poor radioresponsiveness and radiotherapy has been reported to induce anaplastic transformation. Surgery has been considered to be the primary mode of treatment for these tumours. The clinical features, response to radiotherapy, survival and prognostic factors of a group of 53 patients with oral verrucous cancers, were studied and compared to patients with oral well-differentiated, squamous cancers, treated during the same time period. The buccal mucosa was the commonest primary site in both groups. 42 patients with verrucous cancer underwent primary radiotherapy and 11 underwent primary surgery. Complete response to radiotherapy was achieved in 76% of patients with verrucous cancer and partial response in 24%. Patients with verrucous cancer had a five year actuarial disease-free survival of 66% and overall survival of 86%. The corresponding survival figures were 43% and 56% in well-differentiated squamous cancers (P = 0.004). Composite stage of disease was a significant predictor of disease-free survival in both groups. None of the 16 patients with verrucous cancers that recurred after radiotherapy, had features of anaplastic transformation. Oral verrucous carcinoma appears to have similar radioresponsiveness and improved disease-free survival, compared to well-differentiated squamous cancers. The treatment policies for other oral squamous cancers are applicable to these tumours.

Evaluation of visual inspection as a screening test for cervical cancer

Visual inspection of the uterine cervix by paramedical personnel has been proposed for the early detection of cervical cancer, as an alternative to routine cytology screening in developing countries. We evaluated the performance of this procedure in detecting precursor lesions and cancer in a study involving 2843 married women in Kerala, India. Two thresholds were used to define a positive test. In the lower one, any abnormality was considered as positive. The cut-off point for the high threshold was one or more of the high-risk findings: bleeding on touch, suspicious growth/ulcer and hard, irregular, oedematous cervix. A Pap smear was performed on all subjects, and a biopsy was done for those with moderate dysplasia and above. A combination of cytology and histology findings was used as the 'gold standard'. Using the low threshold, 1279 (45%) women were positive on visual inspection, and with the higher threshold 179 (6.3%) were positive. There were six moderate dysplasias, nine severe dysplasias, ten carcinomas in situ and 13 invasive carcinomas. With the lower threshold, sensitivity and specificity to detect moderate dysplasia and above were 65.8% and 55.3% respectively; the values for severe dysplasia and above were 71.9% and 55.3% respectively and for invasive cancer were 92.3% and 55.2% respectively. With the higher threshold, the sensitivity decreased considerably (28.9% to detect moderate dysplasia lesions, 31.3% for severe dysplasia and 53.8% for clinical cancer) and the specificity increased to approximately 94%. At a lower threshold, the sensitivity was not satisfactory, and the test was highly non-specific; at a higher threshold sensitivity was even lower. Thus, the test characteristics of visual inspection are not very promising either as a preselection procedure for cytology or as a low-technology measure for cervical cancer screening in developing countries.

Reproducibility and validity of oral visual inspection by trained health workers in the detection of oral precancer and cancer

A randomized intervention trial is in progress in Kerala, India, to evaluate the effectiveness of oral visual inspection by trained health workers (HWs) in the prevention of oral cancer. Fourteen health workers with college graduation as the basic qualification were trained in oral visual inspection to identify oral cancers and precancers among the participants of the screening trial and to refer them for further confirmation and management. The aim of the present study was to evaluate the reproducibility and validity of the screening test provided by the health worker against the reference oral visual findings of three physicians. A total of 2069 subjects who had already been examined were re-examined by the health workers and physicians. The sensitivity and the specificity of the oral visual inspection were 94.3% and 99.3% respectively. There was moderate agreement between the findings of the initial and the repeat mouth examinations carried out by the health workers, which were on average 6 months apart. There was almost perfect agreement (kappa = 0.85) between the findings of the health workers and the physicians in identifying the different types of oral precancerous lesions. The findings of our study indicate that it is possible to train resource persons to perform the oral cancer screening test as accurately as doctors, although experience appears to be a crucial component of health workers' accuracy. The efficacy of such an approach to reduce the incidence of and mortality from oral cancer, however, remains to be proven.

A population-based survival study on female breast cancer in Madras, India

Breast cancer is the second most common cancer among women in Madras and southern India after cervix cancer. The Madras Metropolitan Tumour Registry (MMTR), a population-based cancer registry, collects data on the outcome of cancer diagnosis by both active and passive methods. A total of 2080 cases of invasive female breast cancer were registered in MMTR during 1982-89. Of these, 98 (4.7%) cases were registered on the basis of death certificate information only (DCO), and there was no follow-up information for 235 (11.3%). These were excluded, leaving 1747 (84%) for survival analysis. The mean follow-up time was 43 months. The overall Kaplan-Meier observed survival rates at 1, 3 and 5 years were 80%, 58% and 48% respectively; the corresponding figures for relative survival were 81%, 61% and 51%. A multifactorial analysis of prognostic factors using a proportional hazards model showed statistically significant differences in survival for subjects in different categories of age at diagnosis, marital status, educational level and clinical extent of disease. Increasing age at diagnosis was associated with decreased survival. Single women displayed poorer survival (37.4%) at 5 years than those married and living with spouses (50.0%). The survival rate among those who had more than 12 years of education was higher (70%) at 5 years than that of illiterate subjects (47%). An inverse relationship was seen between survival rates and clinical extent of disease. The need for research to determine feasible public health approaches, allied to coordinated treatment facilities to control breast cancer in India, is emphasized.

Evaluation of multiple micronutrient supplementation in the management of oral submucous fibrosis in Karachi, Pakistan

Oral submucous fibrosis (OSF) is an oral precancerous condition characterized by symptoms such as intolerance to spicy food, altered salivation, progressive difficulty in opening the mouth, and signs like vesiculation, ulceration, blanching, rigidity, and stiffening of the oral mucosa and depapillation and altered mobility of the tongue. It is seen mostly among people of Indian subcontinent origin. The major structural change is extensive fibroelastic scarring of the lamina propria and deeper connective tissues. A combination of micronutrients (vitamins A, B complex, C, D, and E) and minerals (iron, calcium, copper, zinc, magnesium, and others) was evaluated for its efficacy in controlling the symptoms and signs of OSF in 117 compliant subjects in Karachi, Pakistan, in a single-arm preliminary study. The subjects received supplementation for one to three years. Significant improvement in symptoms, notably intolerance to spicy food, burning sensation, and mouth opening, was observed at exit. The interincisor distance deteriorated in 11 subjects (10%) at exit; it was stable in 56 subjects (49%) and improved in 48 (41%). The mean interincisor distance was 19.1 +/- 10.8 (SD) mm at exit compared with 16.2 +/- 7.5 mm at baseline. A significant proportion of concomitant lesions like leukoplakia also regressed at exit. The major outcome from this study was a beneficial clinical response in subjects with OSF to multiple micronutrient intervention, which justifies its further evaluation in well-designed randomized controlled trials in other settings in South Asia.

Global variations in cancer survival. Study Group on Cancer Survival in Developing Countries

Population-based cancer registries from Algeria, China, Costa Rica, Cuba, India, the Philippines, and Thailand are collaborating with the International Agency for Research on Cancer in a study of cancer survival in developing countries. Comparisons with the SEER program results of the National Cancer Institute in the United States, and the EUROCARE study of survival in European countries revealed considerable differences in the survival of patients with certain tumors associated with intensive chemotherapeutic treatment regimes (Hodgkin's disease and testicular tumors), more modest differences in the survival of patients with tumors for which early diagnosis and treatment confer an improved prognosis (carcinomas of the large bowel, breast, and cervix), and only slight differences for tumors associated with poor prognosis (carcinomas of the stomach, pancreas, and lung). With limited resources to meet the challenge of the increasing incidence of cancer expected in the next few decades, health authorities in developing countries should be aware of the importance of investing in a range of cancer control activities, including primary prevention and early detection programs as well as treatment.

Early detection of cervical cancer by visual inspection: a population-based study in rural India

A total of 3784 women aged 35 and above living in 26 villages in rural Maharashtra state, India, were invited to undergo a pelvic examination, to evaluate the performance of unaided visual inspection by trained paramedical workers in detecting cervical cancer. Of this number, 2135 (56.4%) women complied with the invitation. Paramedical workers scored 1120 (57.3%) and 118 (6%) women as having abnormal cervices using the low- and high-threshold criteria respectively. There was good agreement between the visual findings of the paramedical workers and those of a gynaecologist. All subjects had a cervical smear. A total of 10 cervical cancers were detected by cytology/histology. The sensitivity of visual inspection by paramedical workers to detect cervical cancer was 90.0% using the low threshold and 60.0% with the high threshold to define a positive test. The values for specificity were 42.8% and 94.5% respectively. The results obtained by the gynaecologist were very similar. Cost savings implied by limiting cytology/other investigations to approximately half of the population pre-selected on the basis of visual inspection are likely to be offset by the necessity to repeat the test at frequent intervals, repeated follow-up visits and other investigations.