Findings from a new study suggest that both high and low birth weights increase the risk of testicular cancer in men. The reason for this finding is unclear.

A high rate of testicular cancer in young men hints that early life events may play a role in the development of this cancer, lead author Dr. Athanasios Michos, from Harvard Medical School in Boston, and colleagues note. Moreover, various reports have suggested an association with birth weight.

To investigate further, Michos’s team pooled data from 13 studies that were published between 1983 and 2004 and included 5,663 men with testicular cancer.

Relative to men with a normal birth weight (2,500 to 4,000 grams), those with a low birth weight were 18 percent more likely to develop testicular cancer later in life, they report in the International Journal of Cancer. Likewise, men with a high birth weight were 12 percent more likely to develop the malignancy.

A more in-depth look at the data revealed that high and low birth weights were primarily a risk factor for so-called seminoma testicular cancer, not non-seminoma testicular cancer. Unlike nonseminomas, which develop faster and contain various types of cells, the more common form of testicular cancer - seminoma - is made up of a single type of cell that develops from sperm-producing cells.

Further studies are needed, the team concludes, to “elucidate the underling biology that may contribute the increased risk.”

SOURCE: International Journal of Cancer, September 1, 2007.