In the dermal MCT cohort, high mitotic count was associated with what HR for death?

• A. HR 6.2
• B. HR 76.8
• C. HR 8.2
• D. HR 11.1

Answer: (B)

In survival analysis, a hazard ratio compares the instantaneous risk of death between two groups across the study period. A high mitotic count signals aggressive tumor biology, meaning tumors proliferate and progress more quickly, which translates to a higher risk of death over time.

In the dermal MCT cohort, high mitotic count was associated with an extremely high hazard of death: an HR of 76.8. This means that at any given moment, dogs with a high mitotic count had about 77 times the instantaneous risk of death compared with those with lower counts. That magnitude reflects a very strong adverse effect of rapid cell division on survival in this group.

Other shown values would indicate increased risk as well, but none reach the dramatic level of 76.8, making this figure the best representation of how profoundly high mitotic activity worsens prognosis in this specific cohort. Remember that such large HRs can occur in studies with smaller sample sizes or striking group differences, and should be interpreted with context like confidence intervals and study design.