The focus on KRAS is expanding beyond small molecule inhibitors to diverse immunotherapies. Approaches like TCR T-cells, mRNA vaccines targeting KRAS neoepitopes, and novel amphiphil vaccines are being developed to activate a patient's immune system against their specific cancer mutations.

Despite both being keratinocyte-derived skin cancers, basal cell carcinoma (BCC) responds much less robustly to immunotherapy than cutaneous squamous cell carcinoma (CSCC). The pathologic complete response rate to perioperative PD-1 inhibition in BCC is only 23%, less than half the 51% seen in CSCC, highlighting their distinct immunobiology.

T-cells have natural inhibitory signals, or "brakes" (like PD-1), to prevent over-activation. Some cancers exploit this. Checkpoint inhibitor drugs block these brakes, unleashing a patient's existing T-cells to attack cancer cells more aggressively. This approach has been miraculous for cancers like melanoma.

Successful immunotherapies like anti-PD-1 work by shifting the battlefield's arithmetic. They enhance the efficiency of each T-cell, allowing one cell to destroy five or ten cancer cells instead of three. This turns the fight into a 'numbers game' that the immune system can finally win.

Alpha-emitting radiopharmaceuticals physically destroy tumor cells, creating a cloud of debris that acts as a signal for the immune system. This "neoantigenic storm" helps T-cells identify and attack cancer, making checkpoint inhibitors more effective by providing a clearer target.

Unlike in lung cancer, PD-L1 expression levels do not guide treatment for nonmelanoma skin cancers. Patients with low or even negative PD-L1 levels still show significant response to anti-PD-1 therapy, making the test an unhelpful discriminator for treatment decisions.

Patients receiving systemic immunotherapy for advanced skin cancer are still at high risk for developing new, low-risk primary skin cancers. Medical oncologists should not act as default dermatologists; ongoing co-management is crucial to identify and treat these new lesions while the patient is on systemic therapy.

The high efficacy of checkpoint inhibitors in cutaneous squamous cell carcinoma is enabling a "de-escalation" strategy. Upfront systemic therapy can be so effective that it eliminates the need for subsequent morbid local treatments like extensive surgery or radiation, a major benefit for elderly patients.

A powerful analogy for combination immunotherapy: PD-1 checkpoint inhibitors act like releasing the brake on the immune system, reactivating existing but exhausted T-cells. In contrast, a cancer vaccine like NUS209 is the accelerator, creating entirely new T-cells and reactivities that can target the tumor, providing a synergistic effect.