I have not had CA, but I'm in the medical field. Regarding your Restless Leg Syndrome, I do have that. I have found heat and muscle relaxants to help. You could also purchase pneumatic leg cuffs(the kind you see on patients post-op that rythmically compress your legs to mimic you leg muscles moving to propel your venous blood back up towards your heart and lungs to prevent blood clots). I have found the OTC kind in health product magazines and at Target--only about $20! They do help.
Regarding Tamoxifen, this drug does increase your risk of developing blood clots (DVT). Info. for everyone, the 3 major risk factors for developing DVT are: trauma (surgery or injury), stasis (not using your leg muscles to propel your blood, found often in immobile patients who are unable to walk, and those who sit for long periods, and hypercoagulation-which refers to changes found in the blood itself-either from a genetic condition or meds that alter your blood's 'thickness'. Remember, blood is sticky, and if it's just sitting there in your veins and not really moving, it may feel like clotting.
The only thing that keeps your venous blood moving is the calf muscle. And blood that's moving efficiently doesn't really have the time to stop and clot! This is why everyone is encouraged, while driving for long periods, or taking a flight, to frequently either get out and walk, or at least do isometric calf contractions.
This is my first time on this web site, so perhaps I've been too chatty, for which I apologize. My best to you in your noble fight! Peg of My Heart.