Why this study is important

The Sympathetic Nervous System Induces a Metastatic Switch in Primary Breast Cancer — Cancer Res

This study shows that at the very least for breast cancer, chronic stress (non-painful stress) can induce cancer cells to become more metastatic. Chronic stress shifts to a "sympathetic predominance." This make the cancer cells "outside" the primary tumor more aggressive.

So really stress is not a good idea for cancer patients.