A large, new study challenges previous research that suggested vasectomies might increase the risk of prostate cancer or dying from it.
In the latest finding, researchers found no connection between vasectomies and overall risk of prostate cancer, or of dying from the disease.
The American Cancer Society epidemiologists reviewed more than 7,000 prostate cancer deaths, as opposed to the just over 800 prostate cancer deaths that were studied by Harvard scientists in a 2014 study.
"Vasectomy is an effective and inexpensive long-term method of birth control," said new study author Eric Jacobs. "This new, large study provides some reassurance that vasectomy is unlikely to meaningfully increase risk of prostate cancer."
Read: Prevalence of prostate cancer
Jacobs and his colleagues reviewed data on almost 364,000 men aged 40 and older who participated in the Cancer Prevention Study II, a vast research project organised by the American Cancer Society. A total of just over 42,000 men were identified as having had a vasectomy, a surgical procedure that blocks or cuts the tubes that carry sperm from the testicles.
"This cohort [group in the cancer prevention study] was particularly informative because of the large number of fatal prostate cancers, over 7,400 that occurred during 30 years of follow-up," said Jacobs.
In addition, the study authors analysed information on a subgroup of about 66,000 men from the same study. They were followed, starting in 1992, for new diagnoses of prostate cancer. This group allowed the investigators to assess any link between vasectomy and overall risk of being diagnosed with prostate cancer.
Based on this data, the investigators found no link between vasectomy and either the risk of prostate cancer or the risk of fatal prostate cancer.
Read: Early prostate cancer is curable
The findings were published online in the Journal of Clinical Oncology.
Dr Sumanta Pal is a medical oncologist at the City of Hope National Medical Center in Duarte, California. He said, "The current study mitigates concern that vasectomy could potentially be related to the development of prostate cancer, or death related to this disease."
Jacobs noted that the results of the earlier Harvard study, published in the same journal in July 2014, received a considerable amount of media attention at the time. So, it is reasonable to expect that some men considering vasectomy might have become concerned about the procedure, he said.
Surgery and radiation
That study, the Health Professionals Follow-Up Study, sponsored by the Harvard School of Public Health, found that vasectomy was linked with about a 10 percent greater overall risk of prostate cancer and about a 20 percent higher risk of fatal prostate cancer.
"It's not clear why the two studies found somewhat different results," said Jacobs. "It should be noted that the increase in risk of prostate cancer observed in the Health Professionals Follow-Up Study was relatively small, so the results of the two studies are not all that different. Sometimes study results differ by chance."
The American Cancer Society reports that one in seven US men will be diagnosed with prostate cancer in his lifetime. After non-melanoma skin cancer, the disease is the most common form of cancer in men.
Although it's also the second-leading cause of cancer-related death in men (more than 26,000 are expected to die from prostate cancer this year), the American Cancer Society says it can often be treated successfully with surgery and radiation.
Read: How would you know if something was wrong with your prostate?
And many men have slow-growing tumours, so they're more likely to die of another cause than prostate cancer.
PSA blood test
Dr Pal said there are currently no treatments proven to effectively reduce prostate cancer risk.
"However, we do think that early detection is associated with improved outcomes," he said. "The most recent guidelines suggest a tailored approach to prostate cancer screening, taking into account factors such as family history."
The PSA blood test is the standard screening method for prostate cancer. Prostate-specific antigen, or PSA, is a protein produced by cells of the prostate gland. The blood level of PSA is often elevated in men with prostate cancer.
However, there's much debate in medical circles over the value of PSA screening.
Jacobs added that maintaining a healthy weight and quitting smoking may lower risk of the disease.
"Smoking and obesity have consistently been linked with higher risk of fatal prostate cancer," he said.