Updated Jan 30, 2018
A study out of Lund University and Skane University hospital in collaboration with researchers in the UK found that breast cancer patients treated with Tamoxifen who drank 2 or more cups of coffee daily halved their risk of recurrence! As for patients with TNBC, there is less evidence on recurrence. However, women who drank more than 5 cups per day were 57% less likely to develop TNBC. Please see Amanda Chan's article from www.lifescience.com.
What is really exciting for those of us who enjoy coffee is that at this point it appears to be an important addition to a Healthy Diet and Lifestyle. In fact, coffee was removed from the list of potentially carcinogenic foods by WHO in a June 2016. They, instead, designated coffee as potentially protective against uterine and liver cancer.
A large meta-analysis (analysis of multiple studies) published in November 2017 in the British Medical Journal found that high consumption of coffee (3-4 cups/day) resulted in 17% less cardiovascular related death, 15% less cardiovascular disease, and 18% reduction in cancer. Even lower amounts of coffee had benefits with a 13% reduction in cancer risk. The only significant adverse outcomes were seen in pregnancy (low birth rate, preterm birth, and low birth weight).
The benefits from coffee are thought to be derived from the antioxidant phytochemical, chorogenic acid. Coffee also contains vitamin B2 or riboflavin. Decaffeinated coffee also contains chlorogenic acid, though possibly slightly less. Also see the link from the American Institute for Cancer Research.