Yes. Chemotherapy drugs are systemic, and travel throughout the body "mopping up" stray cancer cells. So any other tumors that were present, in addition to the one that was originally found would hopefully shrink or go away altogether. Today chemotherapy is often given prior to cancer surgery for this reason. This is known as neoadjuvant chemo, in which chemotherapy drugs are used to shrink the tumor before it's removed by the surgeon. Studies have shown that for some types of cancer, such as breast cancer and some head and neck cancers, neoadjuvant therapy plus surgery is more effective than doing it the other way around.