Is the 10-15 year life expectancy from the time of diagnosis or from the current time?

Life Expectancy Calculation in Prostate Cancer: From Diagnosis or Current Time

The 10-15 year life expectancy for prostate cancer patients is calculated from the time of diagnosis, not from the current time. This is based on standard medical practice for survival analysis in oncology.

Evidence-Based Rationale

Survival Analysis Definitions

According to the Haematologica guidelines on survival analysis, overall survival is clearly defined as "time from diagnosis (or entry onto the clinical trial) until death of any cause" 1. This establishes the standard practice of measuring survival time from the point of initial diagnosis.

The "10-Year Rule" in Prostate Cancer

The American Family Physician guidelines specifically mention the "10-year rule" for prostate cancer treatment decisions: "a patient with prostate cancer should be treated only if the patient has a comorbidity-adjusted life expectancy of at least 10 years" 1. This rule is applied at the time of diagnosis to determine if treatment would provide survival benefit.

Life Expectancy Calculation

The comorbidity-adjusted life expectancy tables provided in the American Family Physician guidelines 1 show how life expectancy is calculated based on:

1. Age at diagnosis
2. Comorbidity status (number of diseases)

For example, a 50-year-old man at diagnosis with no significant comorbidities would have a life expectancy of approximately 42.69 years, while the same man with 3 or more diseases would have a life expectancy of 14.23 years.

Clinical Application

When applying the "10-year rule" to a patient diagnosed with prostate cancer at age 50:

• The physician evaluates whether this patient is likely to live at least 10 years from that point of diagnosis
• This assessment is made using comorbidity-adjusted life expectancy tables
• Treatment decisions are based on this initial assessment

Why This Matters

Using the correct reference point (time of diagnosis) is critical because:

1. Treatment decisions are made at the time of diagnosis based on projected survival
2. Clinical trials and guidelines report outcomes based on time from diagnosis
3. Risk stratification models use time from diagnosis as their starting point

Common Pitfalls to Avoid

1. Recalculating life expectancy at each follow-up visit: This creates inconsistency in treatment planning and doesn't align with how clinical evidence is structured.

2. Confusing different survival metrics: Overall survival (from diagnosis to death) is different from progression-free survival or disease-free survival, which may have different starting points 1.

3. Failing to account for age at diagnosis: The comorbidity-adjusted life expectancy tables clearly show that age at diagnosis significantly impacts expected survival 1.

In conclusion, when discussing a 10-15 year life expectancy for a prostate cancer patient diagnosed at age 50, this timeframe refers to the period starting from the initial diagnosis, not from the current time or any subsequent point in the disease course.