Should PBS criteria be expanded for tocilizumab in GCA?

Medicines

By Siobhan Calafiore

9 Jul 2024

A more standardised diagnostic approach to giant cell arteritis with less stringent measures for inflammatory markers might improve equity of access to tocilizumab for patients who don’t meet all PBS criteria, rheumatologists say.

In a brief communication for Internal Medicine Journal [link here], they said their study raised questions as to whether ophthalmologically-confirmed visual involvement should be added as a separate PBS criterion for the interleukin-6 inhibitor, especially in the absence of other features of giant cell arteritis (GCA).

Led by the rheumatology unit at Royal Adelaide Hospital, the researchers compared 13 patients (mean age 68, 54% female) receiving tocilizumab through individual patient use pathways with 21 patients (mean age 77, 62% female) receiving PBS-subsidised tocilizumab at two Adelaide Hospitals from March 2020 to July 2022.

Both groups had similar histories of prior polymyalgia rheumatica or GCA, cardiovascular risk, diabetes requiring medication and malignancy. Visual features were also similar between the groups and while jaw claudication and systemic symptoms were more common in the PBS group, this trend was not statistically significant.

Systemic inflammatory response was higher in the PBS group.

When it came to imaging, 43% of MRI scans were positive for the individual patient use group, including two thirds of MR angiograms with sequences specifically focusing on large vessels. This compared with 100% of PBS patient MRI scans, of which 75% were angiograms with specific large vessel sequencing.

Temporal artery biopsies were performed in 69% and 86% of the individual patient use and PBS groups respectively, with 22% and 78% reporting positive results.

Approvals for individual patient use were granted mainly for visual loss as a complication of GCA in patients who otherwise did not meet PBS criteria. This included bilateral visual involvement (n = 2), unilateral visual involvement (5), extensive vasculitis (4), as well as avoidance of prednisolone side effects (2).

Tocilizumab was accessed on the PBS for disease relapse on corticosteroids (7), bilateral visual involvement (3) and unilateral visual involvement (2), avoidance of prednisolone side effects (3), extensive vasculitis (1), relapse despite DMARD therapy (1), relapse after completing earlier individual patient use-approved tocilizumab (1) and up-front without a specified reason (3).

Two patients in the individual patient use group had GCA diagnoses withdrawn after a neuro-ophthalmologist reviewed their cases; one patient had severe glaucoma and the other had non-arteritic posterior ischaemic optic neuropathy.

“Our audit suggests there are distinct subgroups of GCA patients: those with classical GCA features who fulfil PBS criteria and a second more challenging subgroup who, other than having significant visual threats, do not fulfil as many GCA criteria, particularly systemic inflammation criterion,” the authors wrote.

“This subgroup may be at greater risk of corticosteroid complications based on cardiovascular risk factors, including type 2 diabetes. There was also marked heterogeneity in the use of investigations for GCA, reflecting the diagnostic challenge, and the need for process standardisation, particularly to ensure non-GCA causes of acute visual loss are considered.”

They added: “A crucial finding is that patients with visual predominant presentations are still at risk of developing visual loss or extra-cranial LVV complications elsewhere.

“If they do not fulfil PBS criteria for TCZ [tocilizumab] or are not being treated at a public hospital with an IPU [individual patient use] scheme, patients may be unable to afford potentially the most efficacious and evidence-based treatment currently available as not all patients may be able to access TCZ through an IPU scheme, especially in the private sector.”

There was the question of cost-effectiveness, however, with the agent costing about $10,000 AUD per patient per year. They said this should be weighed against the visual and life-threatening risks of sub-optimally managed GCA.

Real-world data from multiple Australian sites would help substantiate the findings and support a recommendation for PBS expansion, they concluded.

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