This observation prompted him to post a query on Twitter: Had others seen this too? He received a stream of threaded replies: Yes, many had, across a slew of cancer types, and they shared their stories.

“I’ve seen the phenomenon of really exploding growth right at the first scan,” Shilpa Gupta, MBBS, told Cancer Therapy Advisor after tweeting about her experience. Dr Gupta is an associate professor in the hematology, oncology and transplantation Division at the University of Minnesota, Minneapolis. She said the accelerated tumor growth is not unique to immunotherapy because she has seen similar tumor behavior in patients on chemotherapy. “But I would say we are seeing more and more of this in immunotherapy now,” she added.

Studies indicate hyperprogression can occur in any cancer type and the incidence may sit between 9% and 29%, depending on various factors.2  By comparison, immune checkpoint inhibitors are believed to provide benefit to approximately 20% of patients.

The first group to investigate the phenomenon found accelerated tumor growth in 9% of cancer patients treated with a programmed cell death protein 1 (PD-1) or programmed cell death ligand 1 (PD-L1) inhibitor as a monotherapy.3 They published their findings in late 2016, and other groups have since reported incidence rates they have observed in patients across various cancer populations.

A French group found hyperprogression in 29% of patients with recurrent and/or metastatic head and neck squamous cell carcinoma who received PD-L1/PD-1 inhibitors.4 An Italian group reported hyperprogression in a quarter of patients with non-small cell lung cancer (NSCLC) during treatment with PD-1/PD-L1 inhibitors.5 Another French group found hyperprogression in 13.8% of patients with advanced NSCLC who received PD-1/PD-L1 inhibitors and 5% of patients who were treated with chemotherapy, making it the first study to show that while hyperprogressive disease has the potential to occur with other classes of therapeutics, the incidence of it is higher with immunotherapies.6

An interim analysis for phase 2 clinical trial revealed high rates of hyperprogression in germ cell tumor patients treated with durvalumab. Specifically, 8 of 11 patients (72.7%) who received durvalumab had hyperprogressive disease. As a result, study investigators closed the durvalumab alone arm to further accrual.7

“The hard part of all of this is that, up to now, it’s still a very ad hoc observation,” Dr Chan said. He said that more institutions need to track hyperprogressive disease.