SUMMARY: The American Cancer Society estimates that about 59,660 new cases of oral cavity and pharynx cancer will be diagnosed in the US in 2025 and about 12,770 patients will die of the disease. According to the CDC, about 46,711 Human PapillomaVirus (HPV)-associated cancers occur in the United States each year (25,689 among women, and 21,022 among men). Cervical cancer is the most common HPV-associated cancer among women, and Oropharyngeal cancers are the most common among men. There has been a significant increase in the incidence during the past several decades, due to changes in sexual practices.
HPV-positive Oropharyngeal Squamous Cell Carcinoma (OPSCC) is an entirely distinct disease entity from HPV-negative OPSCC. Patients with HPV-positive OPSCC tend to be younger males, who are former smokers or nonsmokers, with risk factors for exposure to High Risk HPV. The HPV-positive primary Squamous Cell Carcinoma tend to be smaller in size, with early nodal metastases, and these patients have a better prognosis compared with patients with HPV-negative Head and Neck Squamous Cell Carcinoma (HNSCC) when treated similarly. Expression of tumor suppressor protein, known as p16, is highly correlated with infection with HPV in HNSCC. Accurate HPV assessment in Head and Neck cancers is becoming important as it significantly impacts clinical management. HPV status is considered the most important prognostic indicator in patients with Head and Neck cancer, and p16 status is now included in the American Joint Committee on Cancer (AJCC) Staging System.
HPV-positive OPSCC is more sensitive to chemotherapy and radiotherapy than is HPV-negative OPSCC, which translates to a much better prognosis and survival, when treated with a combination of platinum based chemotherapy and radiotherapy. This treatment however can be associated with substantial morbidity and lifelong toxicities such as dry mouth, difficulty swallowing, and loss of taste. These tumors, typically being more responsive to therapy than their non-HPV counterparts, appear to benefit from reduced radiation doses, potentially minimizing the severe toxicities linked with conventional radiotherapy, without compromising oncologic outcomes.
Adjuvant chemoradiotherapy has been a mainstay of treatment for patients with surgically resected HPV-positive OPSCC, offering excellent oncologic control. However, standard radiotherapy regimens, typically 60-66 Gy with concurrent chemotherapy, are associated with substantial treatment-related morbidity, particularly long-term dysphagia and feeding tube dependence. With the rising incidence of HPV-driven OPSCC in younger patients with favorable prognoses, interest has grown in identifying de-escalated approaches that maintain efficacy while reducing toxicity.
Trial Overview
The MC1675 Phase III trial (NCT02908477), conducted at two Mayo Clinic sites, directly compared a de-intensified adjuvant regimen against the conventional standard of care. Eligible participants were adults with resected, pathologic Stage III–IV HPV-associated OPSCC (≥70% p16 expression) and at least one intermediate-risk pathological feature. Patients had an ECOG performance status of 0-1 and were stratified by extranodal extension and smoking history.
A total of 194 patients were randomized 2:1 to receive either:
- De-escalated regimen (DART): 30-36 Gy delivered in 1.5-1.8 Gy twice-daily fractions over 2 weeks, with Docetaxel 15 mg/m² IV on days 1 and 8.
- Standard of care (SOC): 60 Gy delivered in 2 Gy daily fractions over 6 weeks, with concurrent weekly IV Cisplatin at 40 mg/m².
The Primary endpoint was the cumulative incidence of chronic grade ≥3 toxicity between 3 and 24 months post-treatment.
Key Findings
With a median follow-up of 37.3 months, the trial confirmed that de-escalated adjuvant therapy significantly reduced late high-grade toxicities:
- Cumulative grade ≥3 toxicity: 3% with DART vs 11% with SOC (P=0.042).
- Feeding tube dependence: 2% with DART vs 8% with SOC (p=0.039).
- Most frequent toxicities: Dysphagia (2%) and esophagitis (1%) in the DART arm vs dysphagia (8%), fatigue (2%), pain (2%), and osteonecrosis of the jaw (2%) in the SOC arm.
Importantly, no new unexpected safety signals emerged, and the reduction in morbidity was consistent across subgroups.
Clinical Implications
These findings add to the growing body of evidence that de-intensification strategies can safely reduce long-term treatment burden for patients with HPV-associated OPSCC, a population with excellent baseline prognosis. The DART approach, using half the standard radiation dose combined with Docetaxel, achieved meaningful reductions in swallowing dysfunction and PEG tube dependence, two of the most disabling toxicities after chemoradiation.
While efficacy outcomes were not the primary endpoint, the trial’s results suggest that oncologic control can be preserved even with substantially lower radiation exposure, provided patient selection is stringent. Longer follow-up and confirmatory studies will be critical to define which subsets of patients may benefit most, and whether this regimen could shift practice standards for intermediate-risk HPV-positive disease.
Looking Ahead
The MC1675 trial underscores a pivotal movement in head and neck oncology, tailoring therapy intensity to disease biology and patient risk, rather than applying a uniform high-intensity standard. For the increasing number of younger patients facing decades of survivorship, approaches like DART may offer durable disease control with far less long-term morbidity. Ongoing research will clarify whether such regimens could become a new benchmark for adjuvant treatment in this favorable-risk population.
De-escalated adjuvant radiotherapy versus standard adjuvant treatment for human papillomavirus-associated oropharyngeal squamous cell carcinoma (MC1675): a phase 3, open-label, randomised controlled trial. Ma D, Price K, Moore E, et al. The Lancet Oncology. 2025;26:1227-1239
