Estimating undiagnosed cancers on the RTT waiting list
04/11/2022by Rob Findlay
The most common route to receiving a cancer diagnosis begins (as we would hope) with a referral in which a risk of cancer has already been identified, according to the Routes to Diagnosis project. These are the so-called Two Week Wait (TWW) referrals, who (as the name suggests) are protected by the statutory two week cancer waiting time target in the English NHS Constitution.
The threshold for using the TWW referral pathway is set very low at just “three per cent or higher risk of cancer” – in other words, GPs should use TWW referrals so frequently that 29 out of 30 TWW patients will get the all-clear at diagnosis. Even so, when we look at all patients who eventually receive a cancer diagnosis, less than 40 per cent come through the TWW route.
The second most common route, comprising more than 20 per cent of cancer diagnoses, is an ordinary GP referral. These are not protected by the cancer waiting time targets, but instead fall under the more general referral-to-treatment (RTT) waiting time target which states that 92 per cent of the RTT waiting list (incomplete pathways, in the jargon) should have waited no longer than 18 weeks. But that target has not been met since 2016, and waiting times are even longer following the pandemic – far too long if you have an undiagnosed cancer.
We can use the Routes to Diagnosis figures to estimate roughly how many patients are on the RTT waiting list, who are not on a TWW pathway but will eventually receive a cancer diagnosis, using a four step calculation.
Firstly: we use the Routes to Diagnosis data to estimate how many routes to a cancer diagnosis began with a non-TWW GP referral, over the most recent available time period (the calendar year 2017). The methodology paper for the Routes to Diagnosis study says that, as well as the GP Referral category, “it is possible that the majority of cases in the Other Outpatient and Inpatient Elective routes were originally initiated by a GP Referral”. So let us include in our count:
- all patients in the GP Referral category (68,824 according to the Data Overview),
- half of those in the Other Outpatient category (half of 27,542), and
- half of those in the Inpatient Elective category (half of 5,350),
which adds up to an estimated 85,270 non-TWW GP referrals receiving an eventual cancer diagnosis in 2017.
Secondly: express that as a proportion of all referrals to consultant-led services over the same time period. In 2017 there were 20,047,066 new RTT periods (including estimates for missing data), so non-TWW GP referrals who received cancer diagnoses amounted to about 0.425 per cent of all referrals to consultant led services.
Thirdly: convert the proportion of referrals into a proportion of the pre-diagnosis waiting list. This will turn out to be an easy calculation, but we have to know what we are doing because the logic is important. On the grounds that these are non-TWW referrals for whom cancer is not yet suspected, let us assume that their management is no different to all the other referrals. They therefore leave the pre-diagnosis waiting list at the same rate as any other patient, throughout their wait. So they will comprise 0.425 per cent of every pre-diagnosis waiting time cohort, and therefore comprise 0.425 per cent of the total pre-diagnosis waiting list.
Fourthly: multiply that proportion by the latest estimated number of pre-diagnosis patients on the waiting list. At the time of writing, the most recent available figures come from the Incomplete Commissioner data tables for August 2022. The total RTT incomplete pathways are on the ‘National’ worksheet (7,003,256 patient pathways), and the ‘with Decision to Admit’ (DTA) incomplete pathways are on the ‘National with DTA’ worksheet (1,064,030). The difference is those without a DTA, which is our best estimate of those without a diagnosis: 5,939,226 patient pathways. We multiply this by 0.425 per cent to get our answer.
The result (25,262 at the end of August 2022) is the estimated number of patients on the latest waiting list who will eventually receive a cancer diagnosis, but whose cancer is not yet suspected. They are not protected by the cancer waiting time targets, and will therefore wait as long as everyone else for a diagnosis and decision, currently 43.3 weeks nationally. Because this is far too long to wait for a cancer diagnosis, I argue that waiting times to diagnosis and decison should be reduced first.
To repeat the calculation when future data is published, the sum is:
( (Total RTT incomplete pathways) – (‘with Decision to Admit’ incomplete pathways) ) * (85,270 / 20,047,066)
The latter two numbers are from 2017 and will change when the Routes to Diagnosis study is next updated.
(I am indebted to Carl Baker at the House of Commons Library for pointing out that the Other Outpatient and Inpatient Elective categories should be partially included in the non-TWW GP Referrals.)Return to Post Index