An immunotherapy treatment may be able to slow the progression and reduce the risk of recurrence of the most common form of lung cancer, according to a study involving researchers from three major Montreal hospitals.

Used in conjunction with chemotherapy administered before surgery and again afterwards, pembrolizumab also reduced the presence of residual tumours in patients with operable, early-stage non-small-cell lung cancer (NSCLC).

Some 800 adults with surgically removable stage II or III NSCLC took part in the study, which was conducted at 227 sites worldwide, including the McGill University Health Centre, the Centre hospitalier de l'Université de Montréal and St. Mary's Hospital Centre. Forty-six of these patients were recruited from the Montreal region.

Half were treated with pembrolizumab before and after surgery to remove the cancer, in addition to chemotherapy. The other half were treated in the same way, but with placebo.

Event-free survival at 24 months was 62.4 per cent in the pembrolizumab group and 40.6 per cent in the placebo group.

A viable residual tumor of 10 per cent or less was observed in 30.2 per cent of the pembrolizumab group and 11 per cent of the placebo group. No viable residual tumor was seen in 18.1 per cent of the pembrolizumab group and 4 per cent of the placebo group.

The study's lead author and chief surgeon, Dr. Jonathan Spicer of the MUHC, said in a press release that "this new treatment is another important step in improving outcomes for patients with this common type of lung cancer."

The treatment, he added, "is suitable for all patients with stage II or III non-small cell lung cancer whose tumor is operable. On an annual basis, this represents a large number of patients for whom survival will be significantly improved."

Pembrolizumab blocks a protein called PD-1 on the surface of the immune system's "killer" T cells. This protein prevents T cells from attacking the body's normal cells, which is desirable, but also protects certain cancer cells, which is less so.

Blocking PD-1 therefore enables T cells to seek out, attack and destroy cancer cells. This also opens the door to autoimmune side effects, but the study authors assure us that the "adverse effects resulting from the addition of pembrolizumab were consistent with what has been previously reported in other similar trials combining immunotherapy and surgery."

The conclusions of this study are published in the prestigious New England Journal of Medicine.

This report was first published in French by The Canadian Press on June 20, 2023.