Let me flip this around and change the perspective of the question..
What comes first, Cancer or the drug? (cancer has been here since the creation of life, not PED's)
The etiology of cancer is multifactorial..So many things can be considered in the equation from genetics,molecular finger print, ones environmental surroundings, and all around diet and lifestyle are all factors interacting to produce a possibility..
However, there is NO studies available supporting or suggesting the risk of developing testicular cancer through PED's..
Now GH, by theory it's been linked, but again, there's no study to support this...
Unless we have a group of people "in patient" study,long term, sharing the same diets and same exact biologic make up (carbon copy) living and sharing the same daily routines, and one using peds and the other not.. Then we will never truly know.. People have different lifestyles, and consume different things, live different places, different nationalities and genders, and most of all different races (There has been studies suggesting a direct link with nationalities and types of cancer)..
Conclusion here:
PED'S have no direct link,well at this moment with research..However, your diet may, especially with "some" of these supplement companies that use massive amounts of binders and fillers that posses a shit ton of heavy metals, yielding a slew of health uses over time!