A combination of targeted therapy and immunotherapy has shown promising results in extending overall survival for patients with anaplastic thyroid carcinoma (ATC), a rare and aggressive cancer with a historically poor prognosis. The Phase II single-center study, published in JAMA Oncology, highlights the potential of combining atezolizumab, an anti-PD-L1 immune checkpoint inhibitor, with mutation-directed targeted therapies to improve outcomes for ATC patients.
The trial, conducted at The University of Texas MD Anderson Cancer Center, enrolled 42 patients across three cohorts, each receiving a combination of atezolizumab and a targeted therapy matched to specific mutations. The median overall survival (OS) across all cohorts was 19 months, significantly higher than the historical OS of approximately five months for ATC patients. Notably, patients with BRAFV600E mutations who received atezolizumab, vemurafenib, and cobimetinib achieved a median OS of 43.2 months, marking the longest OS reported to date for systematic therapy in ATC.
Improved Outcomes with Mutation-Specific Targeting
The study's findings underscore the importance of mutation-specific targeting in ATC treatment. In the cohort of 18 patients with BRAF-mutated ATC, the combination of atezolizumab, vemurafenib, and cobimetinib resulted in a 50% objective response rate (ORR) and a median OS of 43.2 months. For the 21 patients with RAS (NRAS, KRAS, or HRAS) or NF1/2 mutations, the combination of cobimetinib and atezolizumab yielded a median OS of 8.7 months and a 14% ORR. In the cohort of three ATC patients without the above mutations who received bevacizumab plus atezolizumab, the median OS was 6.21 months and ORR was 33%.
Addressing Unmet Needs in ATC Treatment
"Patients with anaplastic thyroid carcinoma need treatments that work fast, and we saw promising results with this combination treatment approach. The takeaway from this study is that immunotherapy really does add benefit for patients," said principal investigator Maria Cabanillas, M.D., professor of Endocrine Neoplasia & Hormonal Disorders. "Based on these findings, we currently use this combination as our standard of care at MD Anderson for patients with ATC and BRAF mutations."
ATC is a rare and aggressive malignancy that often develops from differentiated thyroid cancer subtypes. Mutations in BRAF are observed in approximately 40% of thyroid cancer patients and have significant therapeutic and prognostic implications. The study's success in enrolling a relatively large cohort of ATC patients was attributed to its permissive entry criteria, which allowed patients to continue receiving chemotherapy during screening and to administer oral drugs through feeding tubes.
Safety and Tolerability
The researchers reported that the observed side effects were consistent with those seen in previous trials involving these drugs. Common adverse events included fatigue, lymphopenia, diarrhea, and anemia. Serious side effects, such as colonic and esophageal perforations, were reported in a few patients.
Future Directions
"There are no approved and effective therapies for ATC with non-BRAF mutations, and we continue to focus our research in that area," Cabanillas said. "We are working to optimize outcomes for our patients. We want them to live longer and better lives, and this study offers hope for patients with ATC."
Limitations of the study include the absence of a controlled arm and the acceptance of radiation and surgery to remove the primary tumor, which may have contributed to the improvement in survival. However, the researchers suggest that future ATC clinical trials should be designed to allow for surgery, as it may have contributed to the improved survival outcomes in this study.
