Help with understanding cancer online calculators

trinigirl50

Can anyone explain to me the logic behind the online calculators? I know that breast cancer can reappear many years later but my understanding is that the further out you are, the less likely you are to reoccur. If TNs have more chance of reocurring before 5 years and small chance of reoccurring at 15 years why is this not reflected with the online calculators? Why are the survival curves always worse at 15 years than at 5 years? Or am I just not understanding them? I am hopeless at reading stats anyway, but this one I really dont get.

MountainMia

Which ones are you referring to specifically? Can you post a screen shot of the type of curve you're referring to? I can't answer the question but maybe someone else can if you can give more info.

Beesie

The survival data in the online calculators (CancerMath and PREDICT, as examples) is cumulative. The other thing to consider is that mortality stats lag recurrence stats and these models generally provide a mortality stat, not a recurrence stat. If someone has a metastatic recurrence in year 3, with luck this individual might survive for 5 or 10 years, or even longer. So despite the early recurrence, the mortality stat won't reflect this individual until they pass away many years later.

Here's how the data might work (this is just a made up example):

*Metastatic recurrence rate: by Yr 5: 10%...... by Yr 10: 15%...... by Yr 15: 18%

- This reflects a 10% rate of metastatic recurrence in the first 5 years, a 5% rate in the second 5 years, and a 3% rate in the third 5 years, totalling to 18% over the entirety of the 15 years.

*Mortality rate: by Yr 5: 4%....... by Yr 10: 11%...... by Yr 15: 16%

- These are the figures you would see in the online calculators. What they reflect is that over the first 5 years, 4% of the 10% who developed a metastatic recurrence will have passed away. Over the next 5 years, an additional 7% of those who developed a metastatic recurrence (15% by the end of 10 years) will have succumbed to the disease. And over the third 5 years, 4% more of those with mets (18% by the end of 15 years) will have passed, totalling 16% over the full 15 years. At 15 years, 2% of the 18% who have developed mets remain alive, although I don't think the online calculators would show this anywhere.

Does that make sense?

trinigirl50

yes thank you Beesie! I just couldn't get my head around it. I really do think I have chemo brain. I used to be really sharp now I find myself easily befuddled. Thank you for the simple explanation.

trinigirl50

and thank you mountain Mia for the offer.