Abscopal effect in head and neck cancer: a unicorn summoned once every eon?

Abscopal effect is the reduction of tumor lesions located outside the irradiation field, assuming no other active systemic cytotoxic is administered concurrently. The term was first coined by Mole and etymologically is derived from the Latin prefix “ab” which means “position away from” and the word “scopos” which means “target”.2 Hence, abscopal effect is an “effect away from the target”. It is noteworthy that Mole used the term to describe radiation effects to normal organs, not tumors. In specific, he noticed that thyroid depression would appear only when sufficient volume of the abdomen was irradiated. Although the term was introduced in the middle of the 20th century, the first clinical case is often attributed to McCulloch who, in 1908, irradiated the regional lymph nodes of a patient with locally advanced unresectable laryngeal cancer achieving complete remission.3