A Phase II clinical trial has revealed promising results for Talimogene laherparepvec (T-VEC) as a neoadjuvant therapy for cutaneous basal cell carcinoma (BCC). The study, published in Nature Cancer, indicates that T-VEC can effectively reduce tumor size, simplify surgical procedures, and induce a strong immune response, offering a potential new treatment avenue for this common skin cancer.
The research, conducted by a team from MedUni Vienna and University Hospital Vienna, involved 18 patients with BCC who would have required complex surgical interventions, such as flap or skin grafts, due to the size and location of their tumors. Participants received six intralesional injections of T-VEC over 13 weeks before undergoing surgery. The primary endpoint was the proportion of subjects who, after six T-VEC cycles, became resectable with wound closure without needing plastic reconstructive surgery.
Key Findings of the T-VEC Trial
The study demonstrated that 50% of patients achieved tumor size reduction sufficient for direct wound closure, eliminating the need for more complex reconstructive surgery. In a third of the cases, histological examination revealed complete tumor regression, with no viable tumor cells detected. Importantly, no tumors grew during the therapy, and all treated tumors exhibited some level of shrinkage. The overall response rate (ORR) was 55.6%; six patients achieved a complete response (CR), four had a partial response, and eight had stable disease. The average tumor area reduction was 45.4% until surgery.
Principal investigator Christoph Höller, Head of the Skin Tumor Centre at the Department of Dermatology, noted that the treatment was well-tolerated by the patients. Only four patients experienced T-VEC-related adverse events, and no serious adverse events occurred.
Immune Response and Mechanism of Action
In addition to its direct tumor-destroying capabilities, T-VEC was found to enhance immune responses within the tumor microenvironment. Comprehensive analyses revealed a significant increase in CD8+ T cells, CD68+ myeloid cells, and CD20+ B cells, along with a decrease in CD4+ T regulatory (Treg) cells and CD4+ T cells after treatment. This indicates that T-VEC can alter the tumor microenvironment (TME) by activating adaptive and innate immunity.
Spatial profiling showed a substantial increase in CD8+ T cells, CD68+ myeloid cells, and CD20+ B cells infiltrating the interface of tumor islands post-treatment, with a significant decrease in tumor cell density in patients with a remaining tumor post-treatment. Single-cell RNA-sequencing (scRNA-seq) analysis further revealed distinct populations of myeloid cells post-treatment, with Ficolin 1- and complement C1q C chain-positive macrophages constituting the majority.
Implications for BCC Treatment
These findings suggest that T-VEC holds promise as a neoadjuvant therapy for BCC, particularly in cases where extensive surgery poses risks or could lead to disfiguring outcomes. The ability to reduce tumor size and simplify surgical procedures can significantly improve patient outcomes and quality of life.
"This new treatment option for basal cell carcinoma can not only simplify surgery but also help to avoid disfiguring operations and functional limitations," stated Julia Ressler, First Author, Department of Dermatology.
Future Directions
While the results are encouraging, the researchers emphasize the need for larger studies to confirm the benefits of T-VEC and establish broader clinical applications. Further research will focus on optimizing treatment protocols and identifying patient populations that are most likely to benefit from this novel therapeutic approach.
