IMRT confers survival benefit for head and neck cancer

Patients with head and neck cancer who received intensity-modulated radiation therapy (IMRT) had better survival rates than those who received conventional radiation treatment -- the first indication of a survival benefit for the more complex technique, according to a new study in Cancer.

Researchers from the University of Texas MD Anderson Cancer Center examined the outcomes of more than 3,100 patients treated from 1999 to 2007. Some of this group received IMRT, while others were treated with non-IMRT techniques. Those who received IMRT demonstrated better survival rates than those who didn't, the researchers found (Cancer, January 13, 2014).

This was the first population-based study to show that IMRT conferred a survival benefit for patients, in addition to already demonstrated advantages in terms of reducing side effects, according to the authors.

Shaping dose

IMRT has been adopted by many radiation oncology centers due to its ability to shape radiation dose to tumors and spare surrounding healthy tissue. It's been assumed that IMRT's more accurate dose pattern primarily benefits patients by reducing side effects such as xerostomia (dry mouth), and clinical studies have generally supported this contention.

However, IMRT costs more than conventional radiation therapy, leading some health policy analysts to question whether the greater expense is worth it. Complicating the issue is a lack of studies specifically addressing IMRT's impact on patient survival.

To help answer that question, a research team led by Dr. Beth Beadle, PhD, decided to focus specifically on IMRT's effect on outcomes for head and neck cancer as measured by cause-specific survival. In theory, there could be a benefit: IMRT's greater precision allows the delivery of radiation doses higher than the 2 Gy per fraction amount typically used with conventional therapies.

"Historically, conventional 2D and 3D RT uses large fields and a series of field reductions to provide sequentially higher doses to the primary tumor," the authors wrote. "IMRT has the advantage of being able to target the tumor itself with greater conformality and simultaneously reducing dose to normal tissues."

This could produce either better or worse patient outcomes, Beadle and colleagues posited. On the positive side, the higher dose to targeted tissue and lower dose to surrounding healthy tissue could improve outcomes if the technique is performed well. But on the negative side, the tighter margins and higher conformality of IMRT could create the risk of marginal misses and decrease cause-specific survival if performed poorly.

The researchers began their analysis by examining the Surveillance, Epidemiology, and End Results (SEER) database for patients with head and neck cancers who were treated between 1999 and 2007. They identified 3,172 patients who met the study's inclusion criteria. The mean age of the patients at diagnosis was 72.2 years, and 66.8% were male.

In all, 1,056 patients (33.3%) received IMRT, while 2,116 individuals (66.7%) were treated with conventional radiation therapy. Some 58.3% of the patients had cancer of the oral cavity and oropharnyx; 18% had cancer of the larynx; 10.7% had cancer of the hypopharynx; 6.8% had cancer of the nose, nasal cavity, or middle ear; and 6.2% had cancer of the nasopharynx.

Of the total 3,172 patients, 1,783 (56.2%) died, with 888 patients (28%) reportedly dying of causes related to head and neck cancer. However, those treated with IMRT had a statistically significant improvement in cause-specific survival (38.9%), compared with those who received conventional treatment (18.9%, p < 0.0001).

Because of the different sizes of the two patient groups, the researchers then created two equal-sized study cohorts, and again, IMRT-treated patients had significantly better cause-specific survival (hazard ratio = 0.72, 95% confidence interval: 0.59-0.9) than the non-IMRT group.

The authors characterized their findings as "unique" and "controversial," highlighting the fact that IMRT's superior outcomes for both side effects and survival could give it a cost-effectiveness edge over conventional radiation therapy.

"As the population of patients with head and neck cancer grows younger and more prone to both toxicity and recurrence, a technology that could improve both may not only be comparatively more effective but may also be more cost-effective by reducing needs for costly salvage therapy for recurrences and for side effect management expenses, even if the upfront RT costs are higher due to use of a more resource-intensive RT technique," they concluded.