Radiation Therapy Approaches to Head and Neck Cancer

Transcript:Jared Weiss, MD: Most radiation delivered in the US for the head and neck cancer now is probably through intensity-modulated radiation therapy (IMRT). The standard fractionation scheme for this is 70 Gy given in 35 fractions or, Monday to Friday for 7 weeks. For the patient, however, who is not able to get systemic therapy for one reason or another, there are solid data to support the use of BID radiation with at least 6 hours between the fractions.

Robert Ferris, MD, PhD, FACS: Radiation therapy is an important modality in head and neck cancer. I alluded to its use postoperatively. It can also be used in the upfront setting as a curative treatment for early-stage disease, or in combination with chemotherapy for advanced stage. Radiation therapy used to be very nonspecific, very non-targeted, and led to exposure of the radiation beam to the larger areas of the important structures of the head and neck than really were necessary. But that was because the technology had not been developed to use computer-assisted and three-dimensional conformal imaging. We now have, with our radiation therapy colleagues, the ability to use CT scans and even PET/CT scans. Importing these data into the radiation treatment planning to use three-dimensional conformal therapy, or so-called image-guided radiation therapy, and intensity-modulated radiation therapy, where different portions of the anatomy that the tumor may affect can get higher doses and have a very quick and steep drop-off, so that normal tissue is not irradiated as much as in the old days before we had the IMRT or IGRT, image-guided radiation therapy. These advances have dramatically improved the functional outcomes while maintaining the same cure rates because, ultimately, the radiation just needs to get to the tumor cell. And, we prefer not to have it really extend to the normal tissues surrounding.

As technology advanced for radiation therapy, there was concern that conformal modalities might have some marginal misses, as we say, at the edge or the margin of the tumor. And, that in the effort to reduce off-target effects and normal tissue radiation effects, we would not treat the tumor itself. Fortunately, with high-resolution scanning, that’s not really been the case. Now, there is an issue with quality assurance. Just like surgeons have been subjected for years to the vagaries of quality—and some surgeons have so-called good hands and others maybe weren’t as high volume and not able to retain normal tissues while getting all of the tumor out—we now find that our radiation oncologists have the same problem. It takes really high quality, high-volume surgeons with high-quality imaging to do the conformal-associated radiation therapy that avoids missing the tumor and makes sure that the conformal imaging is used to hit the tumor, but not the normal tissues. And so, quality assurance is an important part of that.

One of the technological developments in radiation therapy has been the use of alternate particles. Instead of photons or electrons, the proton therapy was developed. I’m not a radiation oncologist, but some of the characteristics that are beneficial with proton therapy is the ability to have a very steep quick drop-off in areas—for instance, at the base of the skull—where tumors may be very adjacent to some important neural structures, cranial nerves, the brain, and other aspects that we would not want to radiate. So, those are the areas that proton therapy appears to be most useful for at present. However, there’s no definitive study really saying that proton therapy is better than electron or photon traditional radiation therapy. It’s an investigational instrument that is being used quite effectively by those who are experienced. Because it’s quite an expensive device, it’s not available at every center. There are certain centers that have spent and invested that amount. Those are the ones that tend to use it more frequently. But it’s only recently that studies have opened up to allow us to actually compare it to traditional modalities, which I think is necessary.

As I mentioned, radiation therapy is effective, oncologically, but it does have certain side effects that are characteristic, particularly in the head and neck. Xerostomia and injury to the salivary tissues is one of the key side effects. It turns out, that although a dose of 60 or 70 Gy of radiation is necessary to kill a head and neck tumor, it’s really only at 20 or 30 Gy that can injure the salivary gland tissues. And so, in the course of treatment, often a dry mouth, susceptibility to cavities and caries, and other features—because saliva has many functions in the mouth, not just lubrication, and eating, and helping the bolus go down for swallowing, but also immune functions, and antibodies, and other features—are present in saliva. Radiation therapy can cause fibrosis, scar tissue that often replaces muscle that surrounds a region that’s tumor-infiltrated. When you heal, just like when you heal from surgery, a scar is laid down. Non-surgical therapy induces fibrosis, sometimes abnormal scar tissue. And if the scar tissue replaces muscle, then you don’t have flexible, pliable, mobile tissues—which we know swallowing requires flexible, pliable, mobile, muscular tissues. And, then you create a fixed edematous and frozen portion of the anatomy. So, swallowing is another major functional side effect, particularly long-term. Acute effects, such as sores mucositis, and the breakdown of the lining of the mouth leads to pain and sores. Usually this goes away within weeks or months of the radiation therapy, and it’s worsened by chemotherapy. But that’s really the main acute effect.

Transcript Edited for Clarity