I assume that you want to make oil, and for oil, especially in the case of cancer treatment, indica varieties are used, the more relaxed I work with, without euphoria and similar effects... it means that there should be as much indica as possible, the effects should be relaxing, make you sleep, relieve pain, relax your muscles, make you eat and the like... and look with as much thc as possible compared to cbd, it does not have to have an abnormal amount of thc and if it is desirable, but it is important that it has much more thc than cbd.. in the case of cancer, cbd is good, if the oil has effects just like I wrote that it shouldn't have, then it knows how to calm all that down and alleviate the effects, and the medical effect remains the same.
So, for cancer only indica, the more relaxed effects and the more thc compared to cbd, it means the best to take some kush or some old land race variety of indica, nothing like half thc-half cbd, just as much thc as possible.