Pulse ·

Keytruda joins the PBS for more cancers — what's changed

By Dr HB Lo, FACRRM 4 min read
Verdict Yes — worth knowing about

Pembrolizumab (Keytruda) has expanded its PBS listing to include bile duct, ovarian, and Merkel cell carcinomas, joining a growing list of cancers where immunotherapy is now subsidised. Public patients pay approximately $25 per script; without PBS coverage, a course costs around $14,800.

For GPs, this is a reminder that immunotherapy outcomes are no longer confined to specialist trial populations. Five-year survival in advanced melanoma has risen from less than 10% to more than 55% since pembrolizumab became available. That magnitude of change belongs in the conversations you are having with patients navigating a cancer diagnosis.

What just happened

Pembrolizumab (Keytruda), one of the most consequential drugs in oncology over the past decade, has expanded its Pharmaceutical Benefits Scheme listing in Australia to include bile duct carcinoma, ovarian carcinoma, and Merkel cell carcinoma. Public patients now pay approximately $25 per script — compared to around $14,800 without PBS coverage.

The drug, a monoclonal antibody that blocks the PD-L1 protein and unleashes T-cells against tumour cells, was first approved in 2014. Since then it has been listed for an expanding roster of cancers. The survival data behind those approvals is worth sitting with: for advanced melanoma, five-year survival has risen from less than 10% before immunotherapy to more than 55% now. That is not a small shift at the margins. That is a different illness.

The ovarian cancer listing is particularly significant for a female patient population. Ovarian cancer carries a high mortality burden partly because it is frequently diagnosed at an advanced stage. An expanded PBS listing for immunotherapy in ovarian carcinoma represents a different treatment landscape than the one that existed even five years ago.

The both-and

What the evidence shows

Pembrolizumab’s approval record across these indications rests on phase III randomised controlled trial data. For ovarian cancer, the survival benefit reported in the trials informing listing is a 10% improvement — modest in absolute terms, meaningful in a disease with limited second-line options. For bile duct carcinoma, the reported improvement is approximately 9%. For Merkel cell carcinoma, which is rare and until recently had very few systemic treatment options, the data represent a more fundamental change in what is achievable.

The mechanism matters for GPs managing these patients. Pembrolizumab works by blocking the PD-L1 protein that cancer cells use to evade the immune system — it is not a cytotoxic drug. This means the side-effect profile is categorically different from chemotherapy. Immune-related adverse events — pneumonitis, colitis, hepatitis, endocrinopathies, skin reactions — can occur at any point during treatment, and some emerge weeks after the last dose. GPs are increasingly the first clinician a patient contacts when these appear. Knowing the drug is in the history is the first step.

What is genuinely uncertain

Not all patients respond. PD-L1 expression in the tumour is one predictive biomarker, but it is imperfect — some patients with high expression do not respond, and some with low expression do. Biomarker-guided patient selection for immunotherapy remains an active area of oncology research.

The immune-related adverse event profile is also not fully predictable at the individual level. Some patients experience mild, manageable immune activation; others develop serious organ toxicity requiring high-dose corticosteroids and cessation of treatment. GPs in shared-care arrangements with oncologists need clear protocols for recognising and escalating immune-related adverse events early — because the toxicity of checkpoint inhibitors looks different from chemotherapy toxicity and can be missed if the GP is not oriented to the drug’s mechanism.

There is also the question of access equity across the expanded indications. PBS listing brings cost down dramatically, but access still depends on meeting the specific clinical criteria, having an oncologist prepared to prescribe, and living within reach of an appropriate treatment centre. Rural and remote patients with these diagnoses face structural barriers that PBS listing alone does not resolve.

My two cents

For a GP managing a patient who has just been told they have ovarian or bile duct cancer — diseases that carry a heavy prognosis in public consciousness — the fact that an immunotherapy agent is now PBS-listed for those indications is information that belongs in that first difficult conversation. Not as a promise of cure, and not as a replacement for an oncology consultation, but as an orientation: the treatment landscape has changed.

The GP’s role in immunotherapy-era oncology is not to prescribe pembrolizumab. It is to recognise immune-related adverse events when a patient presents with shortness of breath or diarrhoea three weeks into a cancer treatment; to know what drug they are on; to escalate without delay; and to understand that corticosteroids, which a reflex prescriber might reach for to suppress immune reactions, should only be used in immunotherapy patients under oncology guidance — because unguided immunosuppression can blunt a treatment response.

General practice is the safety net for these patients. The drug is now PBS-listed, which means more patients will be on it. That is a good development worth knowing.

Verdict: yes — this PBS expansion materially changes what is available and affordable for Australians with specific cancers. General practice needs to understand the drug and its side-effect profile.

Sources cited

  1. How does the cancer drug Keytruda work? And how is it different to chemo? — Nial Wheate, Macquarie University, The Conversation, 31 August 2026. https://theconversation.com/how-does-the-cancer-drug-keytruda-work-and-how-is-it-different-to-chemo-290808

Frequently asked questions

  • Which cancers does the PBS now cover for pembrolizumab?

    The PBS has progressively listed pembrolizumab across a growing range of cancers. The most recent expansion includes bile duct carcinoma, ovarian carcinoma, and Merkel cell carcinoma. Earlier listings included melanoma, lung, head and neck, bladder, and cervical cancers, among others. Your oncology or GP shared care letters should reflect current PBS indications — confirm with the treating specialist for any individual patient.

  • How does pembrolizumab work differently from chemotherapy?

    Chemotherapy damages fast-growing cells, including cancer cells, but also hair follicles, gut lining, and bone marrow — which produces its characteristic side-effect profile. Pembrolizumab is a monoclonal antibody that blocks the PD-L1 protein. Cancer cells use this protein to disguise themselves from the immune system's T-cells. By blocking PD-L1, the drug allows T-cells to recognise and attack tumour cells. The immune-related side effects are distinct from chemotherapy — they can include inflammatory reactions in the lungs, bowel, liver, and skin — and GPs managing patients on pembrolizumab should be familiar with immune-related adverse events.