Recently the new material GeCH3 has been synthesized, which has shown an en- hanced thermal stability. GeCH3 is thermally stable up to 250 ? C which compares to 75 ? C for GeH. The electronic structure of GeCH3 has been shown to be very sensitive to strain, which makes it very attractive for strain sensor applications. There exist already a few first-principle studies of GeCH3 that also include the effect of SOC. To fully understand the physics behind the electronic band struc- ture close to the Fermi level, we propose a tight-binding (TB) model, including spin-orbit coupling (SOC), for the electronic properties of methyl-substituted ger- manane (GeCH3) that is valid close to the Fermi level. Our TB model is fitted with the DFT results both with and without SOC and it turns out to be in very good agreement with DFT calculations. We applied biaxial tensile strain to ex- amine the effect of strain on the electronic properties of this system and compare our results with DFT calculations. We examined the possibility of a topological phase transition in GeCH3 under biaxial tensile strain. Our claim that there is a transition to the QSH phase, is further corroborated by the fact that we find in fact TRS protected edge states in nanoribbons made out of GeCH3. Also it is shown, using the Z2 formalism, that a topological phase transition from a normal insulator (NI) to a quantum spin Hall (QSH) phase occurs at 11.6% biaxial tensile strain. The sensitivity of the electronic properties of this system on strain, in par- ticular its transition to the topological insulating phase, makes it very attractive for applications in strain sensors and other microelectronic applications.