The field of cancer research has been remarkably transformed in recent years, with a significant emphasis placed on the potential of immunotherapy. Central to these advancements has been a unique subset of immune cells known as gammadelta (γδ) T cells. These T cells are gaining attention due to their innate ability to detect and destroy tumor cells. Additionally, they can be manipulated through T-cell engineering, opening the door to cancer treatments.

T-cell engineering represents a quantum leap in medicine's ability to restructure components of our immune system to fight cancer cells more effectively. While most current therapies have focused on Alpha Beta (αβ) T cells, γδ T cells present unique characteristics that make them attractive alternatives. These include their ability to detect and eliminate a broad spectrum of malignancies without causing graft-versus-host disease.

An appealing development in this field has been the construction of CAR-engineered γδ T cells. The CAR approach equips γδ T cells with synthetic receptors that can recognize specific antigens in cancer cells. These are 'homing devices' that direct the engineered T cells toward tumors. The CAR engineering technology has been combined with γδ T cell activation. This process enhances the tumour-recognizing capabilities, causing the γδ T cells to proliferate and attack cancer cells more efficiently.

Gammadelta T cell activation is an essential aspect of developing effective CAR-engineered γδ T cell therapies. When activated, these cells have the potential to initiate a robust immune response. They display a potent cytotoxic function, target multiple cancers, and show long-term persistence in the body, making them ideal warriors in the fight against cancer.

Practical implementation of this targeted approach necessitates rigorous testing, which brings researchers to the γδ T cell cytotoxicity test. In these tests, the γδ T cells' ability to recognize and kill cancer cells after being engineered and activated is evaluated. During the γδ T cell cytotoxicity test, the performance of the CAR-engineered γδ T cells is scrutinized under various conditions, including different cancer types and levels of malignancy.

Moreover, γδ T cell cytotoxicity testing has been pivotal in revealing some significant advantages these cells have over other immune cells. For instance, γδ T cells respond to a wide range of cancers, including those resistant to other immunotherapies. They also persist longer in the body and are less prone to exhaustion, where T cells lose their ability to function over time.

In conclusion, the research focused on CAR-engineered and activated γδ T cells is breaking new ground in studying immunotherapy for cancer treatment. The tireless efforts to fine-tune T cell engineering, improve methods of γδ T cell activation, and refine the γδ T cell cytotoxicity test are heralding promising prospects for the future. While challenges remain, the unique potential of γδ T cells in cancer therapy provides a beacon of hope, arguably becoming one of the most exciting frontiers in cancer research today. The promise of developing more personalized, durable, and efficacious cancer therapies is no longer a far-off vision, bringing real hope to researchers around the world.