First step towards a non-invasive screening test for early signs of testicular cancer
Researchers in Denmark have discovered a way to detect early signs of testicular cancer before it has started to spread. Their findings are the first step towards developing a simple screening test for men at risk of the disease.
Writing in Europe’s leading reproductive medical journal Human Reproduction today (Thursday 3 March), doctors from the Rigshospitalet in Copenhagen report the first diagnosis of pre-invasive testicular carcinoma in situ (CIS) in a semen sample from a 23-year-old man. The man had been included in the researchers’ study as a supposedly healthy control, with suspected infertility problems but no suspicion of cancer.
There are about 13,200 new cases of testicular cancer each year in Europe and it is the commonest cancer in men between the ages of 20 and 39. Nowadays more than 90% of cases can be cured, especially if caught early. However, it is often difficult to detect the cancer before it has started to spread. This means that surgery is usually accompanied by chemotherapy or radiotherapy, both of which may cause infertility.
The study’s lead author, Dr Christina E. Hoei-Hansen, a doctor and PhD student, said: “In earlier studies it was found that CIS cells could be found in semen samples of patients with testicular cancer. However it was difficult and time-consuming to detect these CIS cells and the methods were not sufficiently reliable to be used for diagnostic purposes in the clinic.”
In a recent study the researchers had found the TFAP2C gene, which produces a protein called AP-2γ (transcription factor activator protein-2), was expressed in CIS and therefore provided a marker for detecting the cancer. “The AP-2γ protein is not expressed in the normal adult reproductive tract, but is abundant in the nuclei of CIS and tumour cells and it does not degrade substantially in semen,” said Dr Hoei-Hansen. “This prompted us to start this current study where we have analysed the value of AP-2γ for detecting CIS and/or tumour cells in ejaculated semen.”
Semen was analysed from 12 patients with known testicular cancer and from a number of control groups, including men with other types of cancers and infertility problems, and a group of apparently healthy young men attending the hospital for other projects.
Dr Hoei-Hansen said: “When we were evaluating the first series of semen samples we detected AP-2γ positive cells in a sample from one of the healthy controls. He was a 23-year-old man who was having a routine semen analysis because he and his partner had been trying unsuccessfully for 18 months to have a baby.” Apart from the AP-2γ positive cells there were no other indications of testicular cancer, but further clinical evaluation, including a biopsy, revealed CIS in his left testicle.
Doctors advised the patient to have surgery to remove the testicle with the CIS, freezing semen samples beforehand. No chemotherapy or radiotherapy was required. In a happy ending to the story, the patient and his partner are awaiting the birth of their first child, which was conceived naturally, without assisted reproduction.
Professor Niels E. Skakkebæk, head of the University Department of Growth and Reproduction, at the Rigshospitalet, said: “To our knowledge, this is the first report of the diagnosis of testicular cancer at the pre-invasive CIS stage in a semen sample from a young patient with suspected infertility, who – if not for the inclusion in our study of AP-2γ – would most probably have been diagnosed much later, perhaps only after an overt tumour had developed. This is a new, simple method of screening, using AP-2γ as a novel marker for CIS. The value of this method for diagnostic use in the clinic requires further, careful validation in a large series of patients and controls, but the preliminary results are promising.”
At present, the preparation, staining and analysis of a semen sample takes just over a day in total, but Dr Hoei-Hansen said that if the test was to be offered more widely, some parts of the analysis would be handled automatically and more efficiently. “We believe the method would be relatively inexpensive,” she said.
Amongst the first 104 patients included in the study, the test detected testicular cancer in 5 out of 12 men with testicular cancer, and when the control patient with CIS was added, this meant the test had a sensitivity of 46%. There were no false-positives, which suggested that the test was highly specific.
Dr Hoei-Hansen said: “The large proportion of negative results in the testicular cancer patients could be due to the small volume of the semen sample used for the test – 50-300 microlitres out of a total normal volume of 3-5 millilitres – thus stressing the need for either repeated analysis or larger volumes analysed. These conditions will be assessed in an ongoing study of a larger number of patients. Negative results could also be due to compression from the tumour obstructing tubules, resulting in few or no CIS cells being shed into semen.” However, she said she was pleased with the sensitivity of this early study.
Prof Skakkebæk concluded: “If further studies confirm that this method could be used as a simple, non-invasive screening test, it could be offered in andrology and fertility clinics to young men at risk of testicular cancer because of atrophic testes, a history of cryptorchidism or who need assisted reproduction techniques. The real advantage would be that young men could be diagnosed at the pre-invasive stage of testicular cancer, when the disease had not metastasised, when only surgery would be required, and not radio- or chemotherapy. With this more gentle treatment, fertility is usually unaffected.”
Emma Mason | alfa