In 1996, former professional road racing cyclist and seven-time Tour de France winner Lance Armstrong, who became a disgraced champion for using performance-enhancing drugs, was diagnosed with testicular cancer. Now, in the new ESPN docuseries Lance, Armstrong discusses, among other topics, whether doping caused his cancer, People reports.

In the first of two episodes, Armstrong is asked whether he thinks using performance-enhancing drugs led to his metastatic testicular cancer (it spread to his abdomen, lungs and brain). His reply? “I don’t know the answer to that. I don’t want to say no because I don’t think that’s right either. I don’t know if it’s yes or no, but I certainly wouldn’t say no.”

Armstrong started doping four years prior to his eventual diagnosis. He notes that the only time he ever used a growth hormone was during the 1996 cycling season, the same year he received his diagnosis. Armstrong wonders whether the drugs meant to help spur a growth in his muscular cells could also have spurred the growth of bad ones, such as cancer cells.

“So just in my head, I’m like ‘growth…growing…hormone and cells.’ If anything good needs to be grown, it does,” Armstrong say in the film. “But wouldn’t it also make sense if anything bad is there, that it, too, would grow?”

According to the Mayo Clinic, human growth hormone (HGH), which enhances muscle mass and performance in athletes, has many side effects, including joint pain, diabetes, carpal tunnel syndrome and an enlarged heart.

Research has also shown that HGH can increase a person’s risk of cancer in general but most particularly prostate cancer, according to an newsletter article published by Harvard Medical School. However, research on the effect of HGH and other performance-enhancing drugs on testicular cancer is lacking.

Lance explores Armstrong’s life from his youth to his notorious career to the present. Tune in to ESPN Sunday at 9 p.m. to watch the second episode of Lance.

For related coverage, read “Cancer Advocate Patrick Dempsey Elected Honorary Captain of U.S. Olympic Team” and “Connor O’Leary — CMO of Testicular Cancer Foundation” by Cancer Health blogger Justin Birckbichler.