When calculating mutation carrier probabilities, which input data/parameters most strongly influence the resulting probabilities?

When it comes to the mutation carrier probabilities, the dominating factors that influence those will be cancer diagnoses in the proband, cancer family history, ages at cancer diagnosis and tumour pathology. The other risk factors (see: What information do the breast and ovarian cancer models use to determine risks?) will influence to some extent the mutation carrier probabilities but their effects are small compared to the effect of cancer diagnosis, family history and pathology.