Fluid retention in lower legs? This might be because you are not taking enough exercise, even while you are sitting you could try to keep your feet and legs in motion. Blood/fluid tends to pool at lower levels so apart from walking, try the following:
A couple of exercises help to prevent fluid from pooling. Do them a few times a day or as you feel the need until you see an improvement.
Leg lifts: Holding the back of a chair for support, lift one leg off the floor and move it backwards, keep you knees straight.
Frequent, short bouts of exercise can help your edema more than infrequent exercise.
Also, you could elevate your mattress when sleeping at night so that your feet and lower legs are above the level of your heart.. you can do this with a few large books or a yoga block if you have access to one.
Try not to sit in a chair too much during the day, if you need to rest lie down flat with lower legs raised.
Hope this is helpful, but as soon as you can summon up the energy, try to walk as much as possible, even a short walk on a flat surface really helps. I know this might seem counter-intuitive, especially when your HGB is on the low side <10 (often the case at diagnosis and for some time after starting TKI therapy) building up your stamina with daily gentle exercise.
When I was first diagnosed my HGB was often less the 8 and I could barely walk 20 metres without having to rest. But with the encouragement of my partner I gradually built up my exercise (just slow walking) and after around 2 weeks I could walk 1 mile without tiring too much.
TKI therapies can suppress the HGB also.... your body will adjust eventually.
Sandy