If cancer exhibits a weakness, exploit it before taking the target away.

That’s what researchers did in a Phase 2, randomised clinical trial showing that adding immunotherapy before surgical removal of stage III-IV melanoma significantly improved event-free survival and produced no more side effects than standard-of-care treatment, which provides immunotherapy only after surgery.

Results of the multicentre trial, led by a team that included UCLA Jonsson Comprehensive Cancer Center researchers, are published in the March 2, 2023 issue of the New England Journal of Medicine.

“This is the first clinical trial demonstrating that neoadjuvant therapy – that given before surgery – is superior to the same therapy given in the adjuvant setting – after surgery,” said Dr Antoni Ribas, director of the Tumour Immunology Programme at UCLA Jonsson Comprehensive Cancer Center, the paper’s senior author. “This is because it is best to turn on the immune system inside the cancer before it is taken out with the surgery.”

The researchers designed the study and treatment regimen on how pembrolizumab – used in this study – and similar drugs, called immune checkpoint inhibitors, are thought to work.

The antibody pembrolizumab is a PD-1 inhibitor; it blocks an immune checkpoint that blunts the immune system’s response to cancer.

The therapy releases the antitumour immune response – often referred to as “taking the brakes off the immune system” – enabling immune cells already existing at the tumour site to proliferate and attack the cancer cells at that place or anywhere else in the body.

“Based on this understanding, removing the bulk of the tumour, along with the tumour-infiltrating immune cells contained in the surgical specimen, is likely to take away some or even most of the potential antitumour immune cells that would proliferate after PD-1 blockade,” said Ribas, who was chair of the SWOG Cancer Research Network’s melanoma committee when the study was designed and launched. “Our theory has been – and this study confirms it – that starting anti-PD-1 blocking therapy before surgery could activate more antitumour immune cells and improve clinical outcomes compared with the same amount of drug delivered after the surgery.”

As first author Dr Sapna Patel says, “It’s not just what you give, it’s when you give it.” She is the current chair of the SWOG Cancer Research Network’s melanoma committee and associate professor of Melanoma Medical Oncology at The University of Texas MD Anderson Cancer Center.

The trial included patients with clinically detectable, measurable stage IIIB-IVC melanoma that could be surgically resected.

Patients were randomly assigned to one of two groups.

Those in the adjuvant therapy group, consisting of 159 patients, were treated with surgery followed by pembrolizumab given every three weeks for a total of 18 infusions.

The 154 participants in the neoadjuvant group received three infusions of pembrolizumab before surgery, followed by the remaining 15 infusions after surgery.

Therefore, both study groups received the same drug and the same total number of 18 infusions, with the only difference being the timing of surgery.

The researchers found that at two years 72% of patients in the group receiving neoadjuvant pembrolizumab followed by adjuvant pembrolizumab were free of events (inability to get surgery, recurrence of the melanoma or death) compared to 49% of the patients in the adjuvant pembrolizumab alone group.

Dr Bartosz Chmielowski, clinical professor of medicine in the division of Haematology-Oncology at UCLA and study co-author said the study’s findings could change the way high-risk melanoma is routinely treated.

“The study highlights that the timing of administration of an immune checkpoint inhibitor relative to surgery can have a large effect on patient outcomes, even though the same systemic therapy was given to both study groups,” Chmielowski said. “Our results demonstrate a significant benefit when immunotherapy is started prior to surgery to generate an immune response while the bulk of the cancer and the anti-tumour immune cells remain intact.”

Article: Neoadjuvant–adjuvant or adjuvant-only pembrolizumab in advanced melanoma

Source: University of California - Los Angeles Health Sciences