After doctors successfully removed a melanoma from J.P. Rodriguez’s back in 2006, he resumed his life – working, spending time with family and not thinking much about the disease.

But in 2008, J.P. began to experience headaches, weakness and even a blackout.

Doctors couldn’t figure out the problem until J.P.’s wife mentioned his cancer history during an ER visit. Knowing melanoma can spread, the doctor ordered an MRI. It...