Lung cancer screening in Ontario: how far we’ve come, and where it’s going

Not many things in surgery let you change the ending of the story. Lung cancer screening is one of them. Let me tell you why I became such an early believer — and where I think it’s heading next.

Why I started screening in 2014

In 2014, I started a lung cancer screening program at William Osler Health System. The reason was a landmark study in the New England Journal of Medicine that had just changed how I thought about the disease: it showed that screening high-risk people with a low-dose CT scan — rather than a chest X-ray — reduced deaths from lung cancer.¹ That was a genuine turning point. For the first time we had strong evidence that we could find lung cancer early enough to change the outcome, not just diagnose it sooner.

What early detection changed — in my own practice

I can describe the difference in a sentence, because I’ve lived it. For much of my career, most of the lung cancer patients I met were already at stage 3 or 4 — too advanced for surgery. Far too often I couldn’t offer an operation at all, and having to tell someone that was one of the most disappointing parts of the job. Today, screening lets us find lung cancers at stage 1 or 2, before they advance — so now I can operate to remove the tumour, and often cure it, usually through small incisions using minimally invasive (keyhole or robotic) techniques. Same disease, completely different conversation.

A disease worth catching early

Lung cancer is the leading cause of cancer death in the world — which is exactly why finding it early matters so much. Smoking is the biggest risk factor by far, but it isn’t the only one: exposure to radon (a natural radioactive gas that can build up in homes), asbestos exposure, and a family history of lung cancer all contribute. You don’t have to be a lifelong heavy smoker to be at risk — and that’s part of why deciding whom to screen takes more than a single number.

How lung screening works in Ontario today

What began as scattered, individual efforts like ours has become an organized, province-wide program. The Ontario Lung Screening Program offers eligible high-risk adults a low-dose CT scan — a fast scan that uses a fraction of the radiation of an ordinary CT. In broad strokes, it is aimed at people roughly 55 to 74 who have smoked daily for many years, with a trained navigator confirming eligibility through a risk assessment, and entry coming through a referral from your primary-care provider. Those navigators guide people through their results and any follow-up, and connect anyone who wants it to help with quitting. The program grew out of a 2017 pilot and now runs at screening sites across Ontario.

Who is — and isn’t — a good candidate

Here is where it gets more sophisticated than “are you a smoker?” The best way to decide who benefits from screening isn’t age and smoking alone — it’s a person’s calculated risk. Ontario’s program uses a validated risk-prediction model, the PLCOm2012 model, developed by the Canadian researcher Dr. Martin Tammemägi, which combines factors such as age, smoking history, family history and others to estimate an individual’s actual risk of lung cancer.² If that risk is high enough, screening is likely to help. If it’s low, the small downsides of screening — false alarms, incidental findings and follow-up scans — can outweigh the benefit. As with any test, screening is a tool for the right person, not for everyone.

Where screening is going next

This is the part I find genuinely exciting. A few directions stand out:

• Sharper risk prediction. Better models — increasingly adding genetic and genomic information to the clinical picture — will help target screening even more precisely to the people who will benefit, and spare those who won’t.
• Blood tests for cancer DNA. Circulating tumour DNA (ctDNA) — tiny fragments of cancer DNA that can be detected in a blood sample — is one of the most promising ideas in the field. The appeal is obvious: a simple blood test that could complement or help triage CT screening. The honest caveats matter too — today, ctDNA tests are not sensitive enough to reliably catch early-stage lung cancer, they can produce false positives and false negatives, and they are not a substitute for a CT scan. They are a very active area of research, not yet standard care.
• Combining tools. The likely future isn’t one test replacing another, but genomic risk, blood-based markers and low-dose CT working together — screening the right people, and reading their scans more intelligently.

Dr. Kashif Irshad, MD, MSc, FRCSCThoracic & benign esophageal surgeon. This article is general information, medically reviewed September 2026. About Dr. Irshad →