Something I learned after reading lots of research on breast cancer, pay attention to what the discussion is about. When we talk percentages and endpoints, what criteria is this based on?

When you’re told life expectancy is 80% after 15 years they probably mean OS, overall survival. So, say, 80% doesn’t sound reallly bad, but what is my RFS, recurrence free survival, or DFI, disease free interval? See acronyms below, with link.

I’ve become more concerned with recurrence and the expected time lapse (interval) before the next recurrence. My decision is based on my DCIS which was fully removed but has a high recurrence rate, and a 50% chance of being invasive at recurrence. So my current OS is a good number, but between now and later I have a high likelihood of getting another cancerous lesion (great, just keep cutting these things out!) but it could be invasive, which then lowers my OS. And next step, being in a metastatic state is definitely a different beast.

Also be aware of how “risk” is discussed. Most often we are told the relative risk, not absolute risk.
For instance, if you’re told that a treatment can cut your risk in half for getting an invasive cancer recurrence:
And it is known, in this example, that for every 100 women, 30 (30%) will have a recurrence.
RR Relative risk: They are looking at 50% of the 30 that had a recurrence. 15 could potentially have an invasive cancer recurrence.
AR Absolute risk, though, is 15%. For the same group of women, for the same treatment. That is because absolute risk is looking at how many (15) of the entire group (100) actually had an invasive cancer recurrence.
50% does look better than 15%. But be clear about the percentages. When it is said that there is 50% risk, they may not mean 50 out of 100 won’t have a recurrence, it may mean 15 out of a 100.
To be fair, doctors are giving us numbers that come directly from research. Their medical license states that they must use accurate data in their treatments and recommendations. If the research outcomes used RR and OS then those are the numbers usually shared.
See a good explanation on RR below, and link.

Acronyms used:
DDFS, distant disease-free survival; DFS-disease-free survival; DRFS, distant relapse free survival; IBCFS, invasive breast cancer-free survival; IBR, ipsilateral breast recurrence; IBTR, ipsilateral breast tumor recurrence; IDFS, invasive disease free survival; LRR, locoregional recurrence; OS, overall survival; RFI, recurrence-free interval; RFS, recurrence-free survival
From the Standardized Definitions for Efficacy End Points (STEEP)
https://ascopubs.org/doi/10.1200/JCO.20.03613

Risk:
“Absolute risk refers to the actual probability of an outcome occurring in a specific group regardless of any other factors. In this case, it would be the chance of being struck by lightning. Relative risk on the other hand, compares the risk of an outcome between exposed and unexposed groups.”
https://www.osmosis.org/learn/Relative_and_absolute_risk