New Findings on ‘Exceptional Responders’ to Cancer Therapies

By Roxanne Nelson, RN, BSN

A small percentage of patients with cancer show exceptional responses to treatment and survive significantly longer than patients with clinically comparable tumors, despite having advanced disease.

An ongoing research project is studying why some patients have exceptional responses. The researchers have found particular molecular features in the tumors of about a quarter of these patients. In some cases, there are multiple rare genetic changes in the tumor genome. In other cases, the tumors are infiltrated with certain types of immune cells.

The findings were published online November 19 in Cancer Cell. They come from a genomic analysis of tumor biopsy specimens from 111 patients who were identified by the National Cancer Institute’s (NCI’s) Exceptional Responders Initiative, a national project launched in 2014.

An exceptional responder is defined as an individual who achieves a partial or complete response to a treatment that would be effective in fewer than 10% of similar patients. For exceptional response, the duration of response is at least three times longer than the usual median response time.

In this study of 111 such patients, about one quarter (24%, n = 26 patients) were found to have tumors in which there were molecular features that could potentially explain exceptional responses to treatment.

“We won’t be able to identify, in every patient, which particular drugs will be beneficial,” said Louis Staudt, MD, PhD, director of the NCI’s Center for Cancer Genomics, who co-led the study. “We are nowhere near that. But what it does say is that we have identified particular mutations, some of which we knew about in some types of cancer but can also occur less commonly in other cancer types.”

Staudt noted that these mutations can “illuminate” the path that the cancer will take — and potentially can be used to predict whether the cancer will be aggressive and will require treatment or could be managed with surveillance. This is why this research can be useful in the short term, he said.

“In the longer term, this is the kind of research that inspires future work,” he told Medscape Medical News. “That would encompass clinical trials involving drugs that target some of the pathways we found to be genetically inactivated in some of these responders.”

These results support the use of genetic testing in routine clinical care, he said.

Earlier this year, the NCI team published the results of a pilot study that affirmed the feasibility of this approach. Of the more than 100 cases that were analyzed, six were identified as involving potentially clinically actionable germline mutations.

“Curiosity Drove the Research”

“We had these wonderful and gratifying experiences with our patients, so we were immediately curious how that happened, so it was pretty much that curiosity that drove a lot of this work,” said Staudt.

In the current study, Staudt and colleagues used multiple genomic methodologies to detect mutations, copy number changes, aberrant methylation, outlier gene expression, and the cellular makeup of the tumor microenvironment.

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