Radiotherapy dose, volume de-escalation yields favourable oncologic outcomes in HPV+ OPSCC
In the treatment of patients with human papillomavirus-positive oropharyngeal squamous cell carcinoma (HPV+ OPSCC), de-escalating dose and volume of radiotherapy (RT) or chemoradiotherapy (CRT) based on response to induction chemotherapy appears to positively affect oncologic outcomes and reduce toxicity, according to data from the phase II OPTIMA trial.
OPTIMA included 62 HPV+ OPSCC patients who received three cycles of carboplatin/nab-paclitaxel. Researchers assessed treatment response using Response Evaluation Criteria in Solid Tumors 1.1 and grouped the patients as follows: low-risk (≤T3, ≤N2B and ≤10 pack-year history [PYH] of tobacco; n=28) or high-risk (T4 or ≥N2C or >10 PYH; n=34).
Low-risk patients with ≥50-percent response received 50 Gray (Gy) RT (RT50), while low-risk patients with 30–50 percent response or high-risk patients with ≥50-percent response received 45 Gy CRT (CRT45). Patients with lesser response received the standard 75 Gy CRT (CRT75). RT/CRT was limited to the first echelon of uninvolved nodes.
Seventy-one percent and 21 percent of individuals in the low-risk group received RT50 and CRT45, respectively, whereas 71 percent in the high-risk group received CRT45. The median follow-up was 29 months.
The primary endpoint of 2-year progression-free survival was 95 percent in the low-risk group, 94 percent in the high-risk group and 94.5 percent (within the 11 percent noninferiority margin) in the historic control group. The respective overall survival rates in the low- and high-risk groups were 100 percent and 97 percent.
In terms of safety, grade ≥3 mucositis occurred in 30 percent, 63 percent and 91 percent of individuals who received RT50, CRT45 and CRT75, respectively (p=0.004). The corresponding rates of any percutaneous endoscopic gastrostomy-tube use were 0 percent, 31 percent and 82 percent (p<0.0001).
The findings warrant further evaluation of induction-based de-escalation strategy in large multicentre studies, according to the researchers.