The lymph-node station map

All three metrics, in full

The same content as the slides above, without the carousel.

Metastatic rate

Of the patients in whom a station was actually removed and examined, the share that had tumour in it.

metastatic rate (%) = station-positive patients / patients whose station was examined × 100

Denominator: Patients in whom that station was dissected and pathologically assessed — not the whole cohort.

In plain English: How likely this station is to harbour disease, among the patients where someone looked.

Watch out: A station nobody dissects has no metastatic rate, not a rate of zero. Read it next to the dissection rate below.

Dissection rate

How often the station was removed at all, across the cohort.

dissection rate (%) = patients whose station was dissected / patients in the cohort × 100

Denominator: Every patient in the cohort, whether or not that station was touched.

In plain English: How consistently the station is being sampled — and therefore how much weight its metastatic rate can carry.

Watch out: A low dissection rate means the metastatic rate above rests on a small and possibly selected subset of patients.

Efficacy index

The Sasako index: how much survival benefit removing a station could plausibly deliver.

efficacy index = metastatic rate (%) × survival of the station-positive patients (%) / 100

Denominator: Both factors carry their own denominators; the index is null — never a partial product — when either is unavailable.

In plain English: A station scores high only if it is both often involved and its involved patients go on to survive.

Watch out: A high metastatic rate alone does not make a station worth clearing; if nobody positive at that station survives, the index is near zero.