IMRT NEW STANDARD FOR CERVICAL CANCER

For women who receive radiotherapy after undergoing hysterectomy for high-risk cervical cancer, image-guided intensity-modulated radiotherapy (IG-IMRT) is superior to three-dimensional conformal radiotherapy (3D-CRT) at reducing late gastrointestinal (GI) toxicity and is similarly efficacious, according to new findings.

"IG-IMRT should represent the new standard of care for postoperative pelvic radiation therapy in women with gynecological cancers," said study lead author Supriya Chopra, MD, of the Tata Memorial Center in Mumbai, India.

She noted that the study, known as PARCER, is the first in gynecologic cancer to show the impact of advanced technology in reducing long-term morbidity and thus improving the experience of survivors.

At 4 years, rates of late GI toxicity of grade 2 or higher in the IG-IMRT and 3D-CRT arms were 19.2% and 36.2%, respectively (P = .005). Rates of toxicity of grade 3 or higher were 2.0% and 8.7%, respectively (P < .01).

Chopra presented the results at the American Society for Radiation Oncology (ASTRO) 2020 Annual Meeting, which was held online.

Postoperative radiotherapy is indicated for women with cervical and endometrial cancers who have high-risk features, but long-term follow-up has shown an increase in GI symptom burden and toxicity in long-term survivors after adjuvant radiotherapy.

"The uptake of IMRT has been relatively slow in gynecological cancers," said Chopra. She explained that previous data suggested a benefit with the use of IMRT, but long-term postoperative effects were unclear.

The new data amount to a "practice-change use" of IMRT for this indication, said Sue Yom, MD, PhD, of the University of California, San Francisco, who was not involved with the study. "I see this as having potentially important future impacts on clinical practice."

I see this as having potentially important future impacts on clinical practice. Dr Sue Yom

Yom explained that although there have been studies in the United States on the use of postoperative IMRT for pelvic cancer, "this is the first phase 3 study that has shown definite long-term advantages with the use of IMRT, and I would consider it confirmatory."

In 2015, the preliminary results of PARCER were presented at the plenary session at ASTRO. The results showed that patients treated with IG-IMRT had fewer late GI toxicities at a median follow-up of 20 months. However, the difference between groups was not statistically significant in this earlier analysis.

Now at 49 Months' Follow-Up

The study was conducted in three clinical sites of Tata Memorial Center and included a total of 300 patients with cervical cancer. The patients had undergone type III hysterectomy and had intermediate- or high-risk features, or they had undergone type I/II hysterectomy necessitating adjuvant chemoradiotherapy. They were randomly assigned to IG-IMRT (n = 151) or 3D-CRT (n = 149). Most patients (117 in the IG-IMRT arm and 114 in the 3D-CRT arm) received concurrent chemotherapy.

The primary endpoint was late GI toxicity of grade 2 or higher. Follow-up included clinical and quality-of-life evaluations, which were conducted every 3 months for 2 years and then every 6 months for years 2 to 5.

Chopra and colleagues evaluated 11 different GI-related side effects. Differences emerged over time between the two groups. Among the group that received IG-IMRT, significantly fewer patients reported moderate to severe acute diarrhea (17% in the IG-IMRT arm, vs 27% in the 3D-CRT arm), late abdominal bloating (14% vs 28%), bowel obstruction (1% vs 7%), and anorexia/appetite loss (1% vs 7%).

Overall, for patients treated with IG-IMRT, grade 2 toxicity-free survival rates were significantly higher (78% with IG-IMRT vs 57% with 3D-CRT; P = .0009), as were grade 3 toxicity-free survival rates (97.6% vs 81.6%; P = .001).

As noted above, rates of disease-free survival were similar for both groups (73% with image-guided IMRT vs 68% with 3D-CRT; P = .30).

Funding for the study was provided by the Department of Science and Technology and the Department of Atomic Energy, Clinical Trials Center, in India, and by Varian International and the Terry Fox Foundation. Chopra and Yom have disclosed no relevant financial relationships.

American Society for Radiation Oncology (ASTRO) 2020 Annual Meeting. Abstract 2, presented October 26, 2020.

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