Genetic Tests Enable New Treatments for Rare Cancers

DNA sequencing has opened the door to new treatments for rare tumors , many of which do not even have a standard treatment. If DNA sequencing in patients with these rare tumors identifies mutations described in common cancers, targeted drugs against these mutations may be used. A clinical trial presented at ESMO 2017, testing multiple drugs in multiple cancers, demonstrated that through precision oncology research , existing targeted cancer drugs have the potential for use outside their approved indications in other cancers, especially rare tumors without a standard treatment.

A Treatment Option Matching the Tumor’s Genetic Profile

In this approach, genetic tests also known as whole-genome sequence analysis, exome sequencing and similar names are used to screen cancer-associated mutations , after which researchers look for an available drug targeting them. If a meaningful mutation is found together with a drug targeting it , treatment is organized according to the tumor’s genetic characteristics regardless of the cancer type for which the drug was previously approved.

European Oncology Congress presented a basket-type clinical trial, approximately 40 Dutch hospitals in a precision oncology network provided around 2000 biopsies from patients with metastatic cancer. These tumor tissue samples then underwent whole-genome sequencing (sequence analysis). The study had access to drugs from 10 different pharmaceutical companies, totaling 19 drugs. By September 2016, approximately 250 patients had enrolled; of every 3, 1 began treatment matched to the tumor’s genetic profile. Ultimately, %37 of these patients benefited from targeted therapy.

What Is the Clinical Significance of This Result?

• It appears that genetic tests, whose names we once only heard and which we later used only in a small number of patients (mostly for inherited cancers), are becoming standard in cancer diagnosis and treatment. For example, today we do not plan treatment for malignant melanoma skin cancer without checking for a BRAF mutation; similarly, in stage 4 non-small cell lung cancers, evaluating EGFR, ALK and ROS1 mutations has become indispensable. 
• However, screening all cancer-associated mutations rather than a specific target is more costly in rare cancers. Nevertheless, finding meaningful mutations in up to %40 of cases with current genetic analyses is an important development for these cancers, many of which have no effective treatment.
• How drug approval and reimbursement bodies, both abroad and in our country, will respond to this development is something we all wonder about.
• These results indicate that as our knowledge of cancer biology and the molecular treatments available to us grows, our ability to treat cancer also increases.