Obesity Increases Risk of Invasive Penile Cancer

• Penile cancer is a rare type of cancer with many risk factors
• Obesity or being obese is a common modifiable risk factor for penile cancer
• Higher the BMI, higher the risk of penile cancer
• Incidence of penile cancer is higher among overweight men

Cancer of the penis is a rare cancer in men in the United States and Europe which accounts for around 0.4-0.6% of all the cancers in the developed countries. Most common risk factors include lack of neonatal circumcision, poor genital hygiene, phimosis (tight foreskin), human papilloma virus (HPV) infection and smoking. Even though HPV infection and poor hygiene are seen in more than half of the penile cancer patients, obesity also has a strong association as it does with other cancer types. Due to the increasing incidence of cancers in obese patients this association between obesity and cancers are being accepted worldwide. Obesity contributes to oxidative stress in the body and is associated with carcinogenesis and chronic inflammatory mechanisms. A study done among hospital patients has already proved that obese population has a higher incidence of invasive penile cancer than non-obese people. But this does not tell about the association in the population level. So Barnes et al did a study comparing people diagnosed with penile cancer and normal population taken from population database to prove the association of penile cancer with obesity.

Obese and Overweight Men are at Higher Risk of Penile Cancer

This is a population level matched case control study comparing a list of people diagnosed with penile cancer which was taken from the State Health Registry of Iowa (SHRI), which is a member of the Surveillance, Epidemiology, and End Results (SEER) Program. Males above the age of 18 residing in Iowa who were diagnosed between 1985 and 2010 were taken for the study. They were diagnosed with invasive penile cancer of squamous cell variety by microscopic examination. These patients were compared with normal people without penile cancer who were taken from the Iowa Department of Motor Vehicles Drivers’ License Database (DLD). This personal information contains name, age and self-reported height and weight. As there are chances of overlap between the 2 lists, the details were compared and the names from the patient list which was in the DLD registry were removed (266 cases from the initial 278 cases from the SHRI) and those who were not diagnosed with penile cancer were segregated.  A total of 266 cases and 798 controls were taken (1:3 matching). 

Body fat was measured using Body Mass Index (BMI) and classified according to World Health Organization norms. The WHO criteria classifies obesity into 3 categories: at or below normal weight (<25), overweight (25–29.9), or obese (≥30). So with the help of the self-reported height and weight, the cases and controls were stratified according to the WHO criteria.

Obesity - A Modifiable Risk Factor for Penile Cancer

The data was used to calculate the incidence of penile cancer among various groups of individuals who were classified based on their BMI. It was found that the diagnosis of penile cancer was more likely in overweight or obese as compared to controls. Another observation was that the incidence of invasive penile cancer was higher with increasing BMI and obesity with odds ratio of 2.64 (95 % CI 1.81-3.86; p = 0.0103) for overweight men and 3.24 (95 % CI 2.07-5.08; p = 0.0002) for obese men. The overall risk of developing penile cancer was increased by 53% for every 5 unit increase in BMI.

The major strength of this study is the ability to collect a large number of cases in spite of the rarity of the penile carcinoma incidence. It also excludes the referral bias due to the case selection source (SHRI and Iowa DLD), which is usually seen in hospital-based studies. The limitations include self-reporting of height and weight rather than actual measurements due data base referral, there is a possibility that we may underestimate the obesity prevalence. Secondly this study was not able to successfully exclude other risk factors like circumcision status, smoking and race.

Weight Loss Should Be Part of Penile Cancer Prevention

In conclusion, obesity is a major causative factor for many morbid long-term health conditions like diabetes, hypertension, heart problems, strokes and cancers which may affect the quality of life a person. But the association of obesity and penile cancer has not been studied in detail before and probably this is the first population based study which was done on that aspect. Due to the morbid nature of invasive penile cancer, its limited treatment option and obesity being a modifiable risk factor for its cause, there is a need for greater emphasis on educating the men who have high BMI to engage in physical activities to lose weight and teach them about the need for regular self genital examination and seek medical help early if required.

Reference:

1. Obesity is associated with increased risk of invasive penile cancer - (https://bmcurol.biomedcentral.com/articles/10.1186/s12894-016-0161-7)

Source-Medindia