Virtually all oncologists, at one time or another, have treated a patient who defied the odds and achieved an unexpectedly long-lasting response. These “exceptional responders” are patients who experience a unique response to therapies that have largely failed to be effective for others with similar cancers.
Genetic and molecular mechanisms may partly account for these responses and may offer clues about why the treatment works for only a few and not for others. To delve more deeply into that area of research, the National Cancer Institute (NCI) began the Exceptional Responders Initiative (ERI) with the goal of identifying potential biological processes that may be responsible, at least in part, for these unusual responses.
NCI researchers have now successfully completed a pilot study that analyzed tumor specimens from more than 100 cases, and the study has affirmed the feasibility of this approach.
Of these cases, six were identified as involving potentially clinically actionable germline mutations.
The findings wereahead of print in the Journal of the National Cancer Institute.
“Clearly, the analysis and validation of these results will prove critical to determining the success of this approach,” write James M. Ford, MD, and Beverly S. Mitchell, MD, both of Stanford University School of Medicine, California, in an
A special case
Molecular profiling technology, including next-generation sequencing, has significantly changed the landscape of the development of cancer therapies, and clinical trials in early drug development are increasingly selecting patients on the basis of molecular alterations.
The ERI grew out of several meetings held by the NCI in 2013 and 2014. It was built on the ability to profile archived tumor material, explained study author S. Percy Ivy, PhD, associate chief of the Investigational Drug Branch in the Division of Cancer Treatment and Diagnosis of the NCI. “This made it possible to collect cases from participating clinicians from all over the country.
“Published cases included patients treated with a targeted therapy but not treated with knowledge of their tumor’s genomics, who then later turned out to have genomic changes that made their tumor exquisitely sensitive to inhibition of a driving pathway,” she said. “There have been published cases as well as cases in the experience of practicing oncologists that seem to do much better than expected.
“We wondered if we could find molecular reasons why tumors respond not only to targeted therapies but also to standard chemotherapy,” said Percy. “If so, we could refine our choice of therapy to patients who are most likely to respond to it.”’
On its, the NCI writes that there was a particular case that triggered the interest in going ahead with this initiative. Mutations in the TSC1 and NF2 genes, which result in a loss of gene function, were detected in a patient with metastatic bladder cancer. In a clinical trial, the patient was treated with everolimus (Afinitor, Novartis), an inhibitor of the mammalian target of rapamycin (mTORC1), and achieved a complete response with a duration of more than 2 years.
In a separate analysis, researchers sequenced tumors from 96 other individuals with high-grade bladder cancer and identified five TSC1 gene mutations. Tumors were sequenced from 13 patients with bladder cancer who had received everolimus. Results showed that 3 of 4 patients with TSC1 gene mutations experienced some degree of tumor shrinkage after treatment; 8 of 9 patients who did not have the mutation experienced disease progression.
The NCI notes that in “subsequent workshops and discussions, it became obvious that all clinicians have seen a few exceptional responders.”