Prostate is one of the leading site of cancer among males in Mumbai, India. The incidence rates have risen over the past decade, though not as remarkable as in the west. Prostate cancer is known to be disease among the older people and with increasing life-expectancy, the incidence of prostate cancer are also likely to increase in the near future. The data from the Indian cancer registries are showing some increases, the increase being more distinct in Mumbai city. In India, it is one of the five leading sites of cancers among males in all the registries.[3] Very little is known about prostate cancer in terms of the risk factors in the Indian population and this has encouraged us to conduct this study for better understanding of this disease.

There are several risk factors that have been implicated in the risk for prostate cancer. Studies elsewhere have shown family history as a strong risk factor.[4] History of diabetes mellitus,[5] height, weight and obesity,[6] smoking and physical activity,[7] body mass index (BMI),[8] vasectomy[9] have been found to be associated with prostate cancer risk.

Patients were interviewed at the out-patient department of TMH, prior to diagnosis. All patients could not be interviewed due to various reasons. The information was recorded in a predesigned questionnaire. After interviewing the patient, cancer cases and controls were segregated based on the diagnosis. The hospital being a comprehensive cancer centre for diagnosis and treatment attracts patients from all parts of India. In general, in a year 25-30% of patients of total registrations are diagnosed as ‘free of cancer’.

Cases were histologically proven cancer cases of prostate. Controls were those that were diagnosed by histology as ‘free of cancer’. There were cases diagnosed as benign prostate hyperplasia (BPH) which were excluded to be considered as ‘controls’. During the period 1999-2001, 290 patients were interviewed. Of these, 123 histologically proven prostate cancer patients (ICD9: 1859) were included as ‘cases’ and 167 as ‘normal’ controls. Thus, there were 123 ‘prostate’ cancer ‘cases’ and 167 ‘controls’ (unmatched) that were considered as eligible entrants for this study. The questionnaire contained socio-demographic information (age, sex, religion, residence), lifestyle habits such as smoking, chewing, alcohol drinking), dietary habits, comorbid conditions including history of diabetes, hypertension, tuberculosis, height and weight for calculation of BMI, family history of cancer, history of vasectomy and number of children. The questionnaire regarding food items were based on recollection of consumption of routine food items prior to one year from the date of interview. Information on food frequency per week was collected but due to incompleteness, this was not taken into account for the analysis. The dietary items were classified as vegetarian diet and non-vegetarian diet. The non-vegetarian diet included items as dry fish, fresh fish, chicken and red meat; red meat included mutton, liver, pork, brain. Consumption of green vegetables was also recorded.

Table 2 shows the OR and confidence interval (CI) for comorbid conditions and personal history. The Table shows the crude OR and the adjusted OR estimates. The crude OR for age, education and religion had elevated risks (though education was not significant), was taken into account for estimating the adjusted risk estimates. Age was a strong determinant for prostate cancer. Those aged above 55 years had an approximately 18-fold excess risk for prostate cancer compared to those aged less than 55 years. Those with family history of cancer did not show any excess risk for prostate cancer (OR = 0.5) in the study group. Though the risk was more than two-fold (OR = 2.5) for diabetic patients compared to non-diabetic patients, it was not statistically significant. While history of hypertension showed a 2.8-fold excess risk for prostate cancer over the non-hypertensive group. Those with BMI greater than 24.9 had a two-fold enhanced risk for prostate cancer when compared to those with BMI less than 25. Number of children and vasectomy did not show any excess significant risk.

Table 3 shows the OR and 95% CI for life-style habits as chewing, smoking, alcohol drinking and dietary habits. The estimates are adjusted for age, religion and education. Smoking was prevalent in 32.5% of cases and 40% of controls, while the proportion of chewers among the cases and controls was 29% and 48.5%, respectively. Similar distribution was observed among cases and controls with alcohol drinking habit. Chewers (OR = 0.4), smokers (OR = 0.9) and alcohol-drinker (OR = 0.8) did not show any excess significant risk compared to the non-habit group, respectively.

It is seen from Table 3, that the proportion of meat-eaters among controls were twice compared to those among cases while the proportion of tea and coffee drinkers, fish-eaters consumption of raw-green vegetables, were similar among both cases and controls. Consumption of ‘raw vegetables’ (OR = 1.0), meat-eating (OR = 0.6), fish-eating (OR = 1.3) did not show any significant increase/decrease in risk for prostate cancer. Similarly neither tea (OR = 0.7) nor coffee drinking (OR = 1.3) showed any additional risk for prostate cancer compared to non-drinkers.

Table 4 shows the risk estimates obtained by regression analysis by adjusting for factors that were found to be significant in the univariate analysis. The Table shows that those aged above 55 years had a 19-fold excess risk, those with hypertension history had a 2.5-fold excess risk and those with BMI greater than 25 had a 2-fold excess risk for prostate cancer.

Age emerged as the strongest determinant factor for prostate cancer in our study as well, which has also been recently shown in an Iran study.[10] The difference in mean age between the cases (64 years) and controls (46 years) were distinct, essentially due to the fact that prostate cancer is known to be an elderly age disease, while those diagnosed as ‘free of cancer’ had some other ailments not linked to prostate, and also the patients were interviewed at the out-patient department. The authors agree that this is one of the drawbacks of the study, but the OR for risk factors has been adjusted for in the analysis.

Chewing of tobacco is common in India. Chewing includes chewing betel leaf with or without tobacco, pan masala or gutka. The present study showed no significant increase in risk for chewers, although tobacco chewing was more common. Although, no enhanced risk was observed for cigarette smokers in a population-based study conducted in Utah, USA;[11] there are other studies which have reported the contrary viz. no increased risk for current smoker but increased risk for pack years of smoking.[12] However, in the present study no excess risk was observed for smokers, in general, for prostate cancer. Tobacco did not emerge as a risk factor, and also due to the fact that the data on duration of tobacco use was incomplete, pack years of smoking or chewing was not considered in the analysis.

Information on alcohol drinking is difficult, but not impossible, to obtain in Indian situations because of the social stigma attached with this habit. The present study did not show any enhanced risk for alcohol drinkers and is in agreement with that reported earlier.[11]

India being a country with varied religious groups, the dietary habits also vary across the religious groups. It is well known that diet has an important role to play in cancer risk. Despite the associations with meat eating, existing studies suggest that vegetarians do not have reduced risk of breast, bowel or prostate cancer and the present study too did not show any excess risk for meat eaters.[13] Although an earlier study indicated a reduced risk for fish eaters, our study did not show any significant reduction in risk for prostate cancer.[14] Tea and coffee drinking did not show any significant risk for prostate cancer in our study.[12]

Studies in literature showed positive association of family history of cancer and prostate cancer risk; however, our study did not show any enhanced risk, even after adjustment for dietary and other risk factors.[4]

Lower risk of prostate cancer among diabetics has been suggested by many, but not all studies. The possible reason for this inconsistency could be due to the fact that studies have not accounted for ‘time since diagnosis’ of diabetes mellitus, treatment duration or have not examined confounding factors such as diet. A Health Professionals Follow-Up Study from 1986 and 1994, in which 1,369 new cases of non-stage A1 prostate cancer were documented in 47,781 men was reported.[5] Prostate cancer was not reduced in the first 5 years after diagnosis (RR = 1.24, CI = 0.87-1.77). In the present study, although patients with a history of diabetes had an elevated risk (OR = 2.5), it was not statistically significant; this could be attributed to the fact that the ‘time since diagnosis’ and also the duration of treatment taken for diabetes was not recorded. Information on history of diabetes was a part of the questionnaire and was based on interview and hospital records; however not all subjects underwent a gylcosylated hemoglobin level test. We know that there is an increase in the incidence of diabetes in India, but unless a study is carried out in detail whether the rise in prostate cancer cases is due to the increase in diabetes incidence, it cannot be said in affirmative; probably the time of diagnosis of diabetes, duration of treatment and dosage details would give an answer in this direction.

The findings on the association of hypertension and prostate cancer have not been consistent. However, the present study showed an 2.6-fold increased risk for prostate cancer for those with a history of hypertension and is in agreement with one of the earlier studies,[15] whereas an other study did not find any association with prostate cancer.[16]

It is known that obesity and physical activity can modulate the endocrine system. Cerhan et al. (1997) demonstrated that greater BMI (wt/ht²) (RR = 1.7 for BMI > 27.8 kg/m² compared with BMI < 23.6; P trend = 0.1) was a risk factor for prostate cancer. The present study showed that those who had a BMI greater than 24.9 (obese) had a two-fold enhanced risk for prostate cancer compared to those with BMI less than 25, which is in agreement with the findings reported in other studies.[7] A Finnish study reported that middle-aged men with the metabolic syndrome were more likely to develop prostate cancer in this prospective population-based study.[17] The association between metabolic syndrome and risk of prostate cancer was stronger among overweight and obese men with a BMI ≥ 27 kg/m² (adjusted relative risk, 3.0; 95% CI, 1.2-7.3) than in lighter men (relative risk, 1.8; 95% CI, 0.7-4.7).

Those who had undergone vasectomy showed a two-fold non-significant risk for prostate cancer, which is in concurrence with an earlier study reported from India.[9] As per the guidelines stated, men who wish to be screened for prostate cancer should have both a PSA test and a DRE.[18] Similarly there was no association between the number of children and prostate cancer risk in the present study.