Despite the efforts of medical researchers to try and identify the possible risk factors (mainly those acting early in life) that are responsible for testicular cancer, these remain largely unknown. At present there are no satisfactory hypotheses to explain the trends in incidence of this condition nor the geographic variations in incidence.
The incidence of this cancer – the most common solid tumour in young men – is still increasing in virtually all countries with the exception of Denmark. In fact, over the past quarter century there has been a clear trend of increasing incidence of this cancer in the majority of industrialized countries in North America, Europe and Oceania. In Canada, a 50% increase in the incidence rate of testicular cancer has been observed over the last 25 years.
Testicular Cancer is Increasing
In 2004, Professor Lorenzo Richiardi from the Cancer Epidemiology Unit in Turin, Italy together with colleagues from other countries in Europe studied cancer registries from eight different northern European countries (Denmark, Estonia, Finland, Latvia, Lithuania, Norway, Poland, and Sweden). They were able to analyse data from more than 27,000 cases of testicular cancer that were diagnosed in men ranging in age from 15 to 64 years. This was a follow up to a previous study carried out by the same group in the 1990s, which involved nine countries around the Baltic Sea.
The earlier study found that the incidence of testicular cancer doubled in 15 to 20 years, with a ten-fold geographic variation in incidence between participating countries. The main finding from the 2004 study was that the incidence of testicular cancer is still increasing in almost every country except Denmark.
The Etiology of Testicular Cancer
Early onset of puberty , adult tallness, sedentary behavior and consumption of fats, milk, and dairy products have all been postulated as being associated with an increased risk of testicular cancer. However, no causal association with any of these factors was found to be convincingly documented
Probably the best known risk factor for testicular cancer is crypto-orchidism or undescended testis, which occurs in approximately 10% of cases. A man born with an undescended testis is four to five times more likely to be diagnosed with testicular cancer in later life compared to a man with normally descended testes. Significantly, about one in ten men diagnosed with testicular cancer give a history of having had an undescended testis.
The risk of testicular cancer is greater if the boy has both testes undescended – and if the testes were located inside the abdomen rather than in the groin, the risk of cancer is even greater.
Surgery for Undescended Testis (Orchidopexy)
In a study including 794 men and nine regions in England and Wales, the United Kingdom Testicular Cancer Study Group concluded that there was indeed an elimination of risk in men who underwent orchidopexy (surgery to mobilize the undescended testis and bring it down to be fixed in its rightful place within the scrotum) before the age of 10 years. A 2007 study from Sweden identified 16,983 men in that country who underwent orchidopexy for undescended testis in the period between 1964 to 1999, and found that the increased risk of testicular cancer was almost halved if orchidopexy was performed before the boy reached the age of 13 years.
Other studies done in Denmark demonstrated that sub-fertile men – especially those who had low sperm counts – had an increased risk of developing testicular cancer. Men having low fertility were found to be twice as likely as normally fertile men to develop testicular cancer.
The associations demonstrated by all these research studies suggest that testicular cancers actually originate in fetal life. Studies also indicate that there is an appreciable genetic component in the etiology of testicular cancer – with a six-fold relative risk in men who have a first degree relative diagnosed with cancer of the testis.
A definitely established major risk factor is prior testicular cancer. A man who has had cancer in one testis has a 25-fold increased risk of developing testicular cancer in the contra lateral testis.
Finally, temporal trends for the two major histologic types of testicular cancer, seminomas and nonseminomas, are similar, which suggests that they have important causal factors in common.
References:
1. Richiardi, Bellocco, Adami et al: Testicular Cancer Incidence in Eight Northern European Countries: Secular and Recent Trends. Cancer Epidemiology, Biomarkers & Prevention December 2004 (13) 2157.
2. Adami H-O, Bergström R, Möhner M, et al. Testicular cancer in nine northern European countries. Int J Cancer 1994;59:33–8
Sanjiva Wijesinha - Dr. Sanjiva Wijesinha, Associate Professor at Monash University medical school, writes on health, travel and medical topics.
