In a groundbreaking phase I clinical trial presented at the American Association for Cancer Research (AACR) Annual Meeting 2026, researchers unveiled a novel therapeutic approach targeting precancerous lesions in the oral cavity. The study demonstrated that intralesional injection of nivolumab (Opdivo), a well-known immune checkpoint inhibitor, can significantly diminish lesion size and reduce the necessity for invasive surgeries among patients harboring high-risk oral lesions. This advancement represents a potentially transformative development in the management of oral precancers, promising to preserve vital oral functions and improve patients’ quality of life.
Oral precancerous lesions afflict approximately 5% of the general population, with variable risk—ranging from 1% to 36%—of progression to frank oral squamous cell carcinoma. This risk fluctuates depending on cellular dysplasia severity and other clinical factors. Traditionally, absence of reliable predictive biomarkers has led clinicians to recommend frequent surgical excisions of these lesions, a practice fraught with morbidity given the oral cavity’s critical role in speech, mastication, swallowing, and respiration. According to Dr. Moran Amit from MD Anderson Cancer Center, who led the study, repeated surgeries not only cause anatomical loss but also significantly impair oral function, especially as the tongue—a central structure for articulation and swallowing—is often involved.
The current standard of care poses challenges: approximately 60% of patients present with multiple lesions and face a 40% risk of lesion recurrence post-surgery. Each successive surgery carries the danger of cumulative tissue loss, severely compromising oral cavity architecture. The imperative to find an effective, less mutilating treatment modality that preserves both function and aesthetics drove the team to explore localized immunotherapy.
Nivolumab, a PD-1 immune checkpoint inhibitor, has previously demonstrated efficacy in reducing tumor burden across various cancers, including head and neck malignancies. However, its systemic administration is associated with significant immune-related adverse events, which are unacceptable in patients not yet diagnosed with cancer. To circumvent systemic toxicity, the investigators hypothesized that a fraction of the systemic dose, when delivered directly into precancerous lesions, might elicit a strong local immune response sufficient to reduce or eradicate dysplastic cells, while minimizing systemic exposure and adverse effects.
The trial enrolled 29 patients possessing at least one histologically confirmed, untreated oral premalignant lesion deemed high-risk due to size, morphology, dysplasia grade, or patient-specific factors. The majority of lesions involved the tongue, underscoring the functional significance of the target tissue. Patients received four cycles, administered every three weeks, of either 10 mg or 20 mg nivolumab injected directly into a single lesion per patient. This design provided a unique opportunity to investigate whether intralesional injection could provoke localized immune activation without systemic effects or influence on untreated adjacent lesions.
Results were remarkable. At a median follow-up of 14.5 months, clinical responses—defined as a decrease in lesion surface area—were observed in 85% of patients. Averaging a 60% reduction in lesion size, many lesions exhibited reductions exceeding 50%. Importantly, therapeutic responses spanned lesions with both high-grade and low-grade dysplasia, a finding suggesting broad applicability. Histologic analysis further revealed that 41% of patients experienced downgrading in the severity of dysplasia, while six patients achieved complete pathological remission, meaning biopsies showed no signs of dysplasia post-treatment.
The durability of responses was highlighted by the fact that more than 82% of treated lesions remained cancer-free at 12 months. For the minority that progressed to cancer, early detection enabled timely surgical intervention, emphasizing the importance of vigilant surveillance. Notably, patients whose lesions responded did not require transoral surgical resections during the follow-up, indicating that intralesional nivolumab can effectively spare surgeries that would otherwise significantly impact oral function.
Pharmacokinetic monitoring found systemic nivolumab levels were consistently ten-fold lower than those observed with intravenous administration, validating the strategy to minimize systemic exposure and attendant toxicities. Adverse event profiles were favorable; most patients reported only mild side effects such as localized injection site reactions, fatigue, diarrhea, and rash. These mild injection-site reactions resolved rapidly without intervention. Rare severe events included individual cases of grade 3 diarrhea, grade 3 hyperglycemia, and grade 4 acidosis. Overall, the treatment was well tolerated.
Patient-reported outcomes further underscored the clinical benefit of this approach. Symptoms associated with swallowing difficulties, mouth and throat soreness, voice changes, taste alterations, and nutritional status either improved or remained stable throughout treatment and follow-up, translating into enhanced quality of life measures. Many patients also reported increased physical activity and enjoyment of life compared to baseline assessments, highlighting the psychosocial benefits of avoiding disfiguring surgery.
A key immunological finding was selective immune activation within injected lesions—characterized by infiltration of CD4+ helper T cells, CD8+ cytotoxic T cells, and activated dendritic antigen-presenting cells. This was accompanied by evidence of adaptive immune engagement. Untreated lesions from the same patients did not display such immune activation, confirming the localized effect of intralesional nivolumab and suggesting minimal systemic immune modulation. These insights deepen the understanding of tumor-immune dynamics and reinforce the potential of localized immunotherapy.
Dr. Amit emphasized the significance of these findings: intralesional nivolumab offers unprecedented efficacy among nonsurgical therapies for oral premalignant lesions, potentially sparing most patients from debilitating surgeries that compromise fundamental oral functions. Even in cases where surgery remains necessary, the substantial reduction in lesion size achieved through immunotherapy allows for less extensive resections, thereby preserving more of the oral anatomy and optimizing post-surgical function and quality of life.
Beyond oral lesions, the implications of this study may have far-reaching impact. Many cancers evolve from precancerous lesions in diverse tissues such as skin, cervix, and colon. The promising results of local immunotherapy administration in the oral cavity raise the intriguing possibility that analogous strategies could be employed as interception approaches for premalignant conditions in other organ systems, revolutionizing cancer prevention paradigms across oncology.
The study’s limitations include its single-arm design without a randomized control group, relatively short follow-up duration, and a sample size not specifically powered to definitively establish efficacy. Despite these caveats, the trial provides compelling proof-of-concept data warranting larger, controlled studies to validate and extend these findings. Continued research will be essential to refine dosing regimens, identify biomarkers predictive of response, and explore combinatorial approaches.
Supported by the Cancer Prevention and Research Institute of Texas, this pioneering investigation exemplifies how precision immunotherapy can be innovatively tailored to intercept cancer development at its earliest stages while minimizing collateral harm. The absence of reported conflicts of interest further strengthens confidence in the integrity of the data presented. The promise of this approach heralds a paradigm shift toward less invasive, immune-based interventions that prioritize preservation of form and function in patients at risk for oral cancer.
Subject of Research: Immunotherapy for precancerous oral lesions using intralesional nivolumab
Article Title: Injectable Nivolumab Halts Progression of Oral Precancerous Lesions, Potentially Sparing Surgery
News Publication Date: April 2026
Web References:
– Clinical Trial: https://clinicaltrials.gov/study/NCT05327270
– AACR 2026 Meeting: https://www.aacr.org/meeting/aacr-annual-meeting-2026/
– Oral Cancer Information: https://www.aacr.org/patients-caregivers/cancer/lip-and-oral-cavity-cancer/
Keywords: oral cancer, precancerous lesions, nivolumab, intralesional immunotherapy, oral dysplasia, immune checkpoint inhibitor, cancer prevention, immune microenvironment, phase I clinical trial, localized drug delivery
