The Verdict on IMRT Plus Doxorubicin in Unresectable Thyroid Cancer

Intensity-modulated radiation therapy (IMRT) appears to be safe and effective for patients with unresectable or incompletely resected nonanaplastic, nonmedullary thyroid cancer, according to researchers at Memorial Sloan Kettering Cancer Center. In addition, delivering IMRT concurrently with doxorubicin may not cause worse toxicity and should be considered to help improve local control and overall survival in this patient population, they reported in the journal Thyroid.

“This is an exciting finding and may help radiation oncologists safely limit radiation to elective regions in the neck, reducing the morbidity of treatment while preserving high rates of local control,” study investigator Thomas H. Beckham MD, PhD, a resident in the Department of Radiation Oncology at Memorial Sloan Kettering Cancer Center, told Cancer Network.

The researchers conducted a retrospective analysis of the safety, feasibility, and outcomes of definitive-intent IMRT and evaluated whether patients receiving concurrent chemotherapy (CC-IMRT) achieved higher rates of disease control and survival vs IMRT alone. A total of 88 patients with gross residual disease (GRD) or unresectable nonanaplastic, nonmedullary thyroid cancer treated between 2000 and 2015 were included.

In this study, 45 patients (51.1%) were treated with CC-IMRT, and 43 patients (48.9%) were treated with IMRT alone. Patients in the CC-IMRT group received weekly doxorubicin (10 mg/m²). At 4 years, the local progression-free survival (LPFS) was 77.3%, and patients in the CC-IMRT group had a higher LPFS (85.8%) compared with IMRT alone (68.8%).

The study showed that the 4-year overall survival (OS) rate was 56.3% for all patients, and those in the CC-IMRT group had a higher OS (68.0%) compared with patients treated with IMRT alone (47.0%).

“This can be a challenging population because there is relatively little information available about how best to manage these patients who have a very high risk for local failure in the neck, where repeat surgery is challenging and local progression is a significant source of morbidity and mortality,” said Beckham.

He added that, on multivariable analysis, receipt of concurrent chemotherapy was associated with a lower risk of local failure and, surprisingly, a lower risk of death. The amount of gross disease did not correlate with local failure. According to Beckham, another interesting finding was that the patterns of failure analysis allowed the researchers to examine the electively treated lymph node regions. They found that failures outside of the thyroid bed and previously involved lymph node regions are uncommon.

Timur Mitin, MD, an assistant professor of Radiation Medicine at OHSU School of Medicine in Portland, said these are very important findings because radiation oncologists are not usually involved in the care with these patients, because they are primarily managed with surgery and radioactive iodine. “They are asked to treat the patients urgently. So, it is kind of a bit too late to intervene effectively,” Mitin told Cancer Network. 

“It was quite exciting to know that we can improve patient outcome[s],” concluded lead study author Nancy Y. Lee, MD, FASTRO, who is vice chair of the Department of Radiation Oncology, service chief of Head & Neck Radiation Oncology, and director of Proton Therapy at Memorial Sloan Kettering Cancer Center in New York.