Cancer in the Marvel World is a rather peculiar disease, not completely incurable, but hardly curable.
The essence of Lille's condition was radiation residue and chemical damage that led to the collapse of his cellular genes, which caused his cells to die off faster and their division functions to malfunction.
Lizard Serum would fix the part of the transgenic lizard responsible for expressing specific traits onto his cells, activating a robust cell division capability and restoring his cellular functions to normal, or even surpassing that of an average person.
However, lizards could also develop cancer, and at a molecular level, genes were naturally damaged by radiation, making it impossible to heal solely through Lizard Serum.
In fact, no pharmaceuticals involving genetic modification could achieve this.
