chemoradiation
Meaning of chemoradiation: Two treatments given in the same weeks so that one sensitizes the tumor to the other, at the cost of harsher side effects.
Definition of chemoradiation
Chemoradiation is treatment in which anticancer drugs and radiation are given during the same period rather than one after the other. The drugs are chosen and timed so that they leave tumor cells less able to repair the damage radiation causes. It is standard care for several cancers of the cervix, anus, head and neck, esophagus, rectum and lung.
Why give both at once?
Radiation damages the DNA of cells inside the treated area, and a cell dies from that damage only if it cannot repair it before dividing. Several chemotherapy drugs interfere with exactly that repair, or hold cells in the phase of their cycle where radiation does most harm. Given in the same week, the drug turns a survivable dose of radiation into a lethal one for the tumor. Given a month apart, each treatment acts alone and the benefit is merely additive. That timing is the whole point of the word, and drug doses used this way are often lower than when the same drug is given by itself.
Where is it standard?
| Cancer | Role of chemoradiation |
|---|---|
| Cervix | Standard for locally advanced disease, in place of surgery |
| Anus | First treatment, sparing removal of the anus in most cases |
| Head and neck | After surgery in higher risk disease, or instead of it to spare the voice box |
| Esophagus | Before surgery, or as the definitive treatment |
| Rectum | Before surgery, to shrink the tumor and reduce local recurrence |
Why are the side effects worse?
The sensitizing effect is not confined to the tumor. Normal tissue inside the treated field is sensitized too, so the mouth ulceration, swallowing pain, skin breakdown or diarrhea that radiation therapy alone would cause arrives sooner and runs deeper. Blood counts fall as well, which radiation to a small field would not usually cause on its own. Reactions of this kind peak toward the end of the course and during the weeks after it. Breaks in treatment weaken tumor control, so holding the schedule against mounting toxicity is the central difficulty of the approach, and supportive measures such as feeding tubes and pain control are planned before it starts rather than improvised. The word chemoradiotherapy means the same thing.
Also known as
Used in a sentence
The tumor was treated with definitive chemoradiation rather than surgery.
Good to know
The defining feature is that the two treatments overlap in time rather than follow one another, and the sensitizing effect applies to healthy tissue in the field as well, so toxicity is greater than either treatment produces alone.