How to deal with metastatic cancer before tumors appear

I think we would have liked the test for the reason that we could have encouraged the doctors to be more aggressive with chemotherapy or found alternative treatments. From a patient's position, it's hard to have a basis for demanding treatment if, from the doctor's perspective, there is "nothing wrong". In my husband's case, the mets weren't diagnosed until several months after they actually showed up on the CT-Scan. The first time they appeared, the diagnosis was inconclusive and the oncologist wanted to "wait and see". After waiting a few months and another CT-Scan - he could definitely see the mets - within that time who knows what could have happened if we were given the option to aggressively treat the metastasis, that obviously was really there. Maybe there is some stage in tumor development where treatments are exponentially more effective and by waiting until physical tumors are visible, you miss that window of opportunity. But I'm not a medical professional and therefore I'm a pea brain.