Findings from a cohort study highlight a potential role of tumor grade for predicting mucosal head and neck squamous cell carcinoma response to immunotherapy, researchers report in JAMA Otolaryngology–Head & Neck Surgery.
The analysis, which was among patients with either high-grade or low-grade recurrent or metastatic mucosal head and neck squamous cell carcinoma (HNSCC) tumors, revealed that tumor grade was independently associated with immunotherapy response.
“Generally, one would expect high-grade tumors to do worse because they are more aggressive,” said Rajarsi Mandal, MD, the study’s lead author. “But it’s thought that high-grade tumors have higher degrees of chromosomal instability with a lot more mutations generated throughout the genome of these tumors ... and we know that higher mutation rates correlate with higher responses to immunotherapy.”
Researchers found that the proportion of patients having a beneficial response to immunotherapy was larger for patients with high grade tumors (12 of 35; 34.3%) than those with low grade tumors (2 of 25, 8.0%) (difference, 26.3%; 95% confidence interval, 7.3%-45.3%). The odds of having a clinically beneficial response to immunotherapy was increased 5.35-fold (95% CI, 1.04-27.37) in patients with high-grade tumors. Among four patients with low-grade tumors and eight patients with high-grade tumors with available tumor mutational burden data, the mean tumor mutational burden was greater for patients with high-grade tumors (mean [standard deviation], 8.6 [5.4] mut/Mb; n = 8) than for patients with low grade tumors (mean [SD], 3.6 [1.1] mut/Mb; n = 4) (difference, 5.0 mut/Mb; 95% CI, −1.4 to 11.4 mut/Mb; Cohen d, 1.2).
“ said Dr. Mandal who is a head and neck cancer surgeon with the Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University, Baltimore.
Previous studies of HNSCC tumors that are refractory to traditional therapies, including surgery, chemotherapy, and radiation therapy, have demonstrated a clinically beneficial response to immune checkpoint inhibitors (ICIs). An association between increased tumor mutational burden and beneficial response to ICIs has been shown in other cancers.
Researchers hypothesized that tumor histological grade may be associated with responses to immune checkpoint blockade, and designed their study to examine the association between tumor grade and immunotherapy response in patients treated with ICIs for recurrent or metastatic mucosal HNSCC.
In a single-center retrospective cohort study, investigators reviewed the medical records of 60 adult patients (mean age, 64.6 years; 85% male) with a primary mucosal HNSCC tumor treated with an immune checkpoint inhibitor (pembrolizumab, nivolumab, ipilimumab, or durvalumab) treated between July 1, 2015, and Jan. 22, 2020. They stratified them into those with low grade tumors (well differentiated and moderately differentiated) and those with high grade tumors (poorly differentiated). A clinically beneficial immunotherapy response, defined as complete response or partial response was the primary outcome.
Thirty-eight patients in the study cohort were current or former smokers. The most common primary tumor sight was at the oropharynx. Outcomes among those with high-grade tumors were improved, compared with those with low-grade tumors, for median progression-free survival (5.9 months vs. 3.3 months), median overall survival (16.6 months vs. 15.0 months, and risk of death (hazard ratio, 0.94).
The study’s main limitation was its small sample size and small number of patients who had a clinically beneficial immunotherapy response.
Dr. Mandal had no conflicts of interest to disclose.