Intensity-Modulated Radiotherapy Promising for Cervical Cancer
By Roxanne Nelson
Medscape Medical News
November 20, 2009 — The use of intensity-modulated radiation therapy (IMRT) has been shown to help limit exposure to surrounding normal tissue, thereby decreasing toxicity, and might be a feasible treatment option in cervical cancer.
In a new study, published online October?30 in the International Journal of Radiation Oncology, Biology, Physics, researchers from Washington University School of Medicine in St. Louis, Missouri, show that this approach also produced better outcomes. Cervical cancer patients treated with 18F-fluorodeoxyglucose positron emission tomography (PET)/computed tomography–guided IMRT had better survival and a lower incidence of treatment-related toxicity than patients treated with non-IMRT radiotherapy.
"We think the use of IMRT is the next logical step in the treatment of cervical cancer," said lead author Elizabeth Kidd, MD, a radiation oncology resident at Washington University. "Many other pelvic malignancies, such as prostate, anal, and rectal cancers, are using IMRT."
Some institutions might already be using IMRT outside of clinical trials, she told Medscape Oncology. "At our institution, all cervical cancer patients are treated with IMRT."
"Cutting Edge" and Promising
Dr. Kidd and her team are pioneers in the treatment of gynecologic cancers, and they are on the "cutting edge" with this study, said Eleanor Harris, MD, who was approached by Medscape Oncology for independent comment.
"It looks promising, and the hope for IMRT is exactly what this study is showing," said Dr. Harris, section chief of the Breast Gynecologic Clinical & Research Divisions and clinical director of radiation oncology at Moffitt Cancer Center in Tampa, Florida. "It looks like they may have better control rates and reduced toxicity. Therapy for cervical cancer is very toxic and the threshold is higher than for other cancers, so anything that will reduce toxicity is very important."
Although these results are promising, they do need corroboration from other centers, she added. "Ideally, there should be a trial, but the next best thing will be reports from different centers."
Improved Outcomes With IMRT
The study examined 452 consecutive patients with newly diagnosed cervical cancer who were treated with curative intent with definitive radiation from June 1997 to September 2008 at Washington University. Prior to March 2005, 317 patients were treated with a combination of whole-pelvis and split-field irradiation, using the institution's "step-wedge technique."
Following an institutional policy change, all cervical cancer patients treated after March 2005 (n?= 135 in this cohort) received PET-guided IMRT, using pseudo-step-wedge intensity modulation. The treatment regimen for all patients also involved external irradiation and brachytherapy, and 85% of the cohort received concurrent chemotherapy.
The mean follow-up for all patients was 52 months (range, 5 to 117 months). Because non-IMRT patients were treated during the earlier phase of the study, their follow-up was longer and averaged 72 months from the end of treatment; the average time for the most recent follow-up in IMRT patients was 22 months.
At the time of the last follow-up, 178 patients had developed a recurrence — 39 patients (28.9%) in IMRT group and 139 (43.8%) in the non-IMRT group. The pattern of recurrence was similar between groups, with the majority of patients experiencing distant recurrences and 10% or less developing a pelvic recurrence only.
The difference in recurrence-free survival between the 2 study groups did not reach statistical significance (P?= .0738), although the IMRT group showed better overall and cause-specific survival (P?< .0001 for both).
Also at the time of last follow-up, the researchers reported that:
247 patients (91 IMRT, 156 non-IMRT) were alive with no evidence of disease
51 patients (34 IMRT, 17 non-IMRT) were alive with disease
122 patients (5 IMRT, 117 non-IMRT) had died of cervical cancer
28 patients (4 IMRT, 24 non-IMRT) had died of intercurrent disease
4 patients (1 IMRT, 3 non-IMRT) had died from treatment-related toxicity.
The incidence of high-grade adverse events was also lower in the IMRT group. Grade?3 or higher gastrointestinal and genitourinary complications were experienced in 6% (8 patients) of the IMRT group, which was significantly lower than the 17% (54 patients) in the non-IMRT group (P?= .0017).
The posttreatment PET findings suggest that long-term recurrence rates and disease-specific survival will be similar for the IMRT and non-IMRT patients, the authors note. "We are continuing to follow the patients, so we could present longer-term outcomes in the future," said Dr. Kidd. "However, we think the present study clearly demonstrates decreased toxicity and no worse recurrence rates with IMRT than with non-IMRT. In previous research from our institution, we showed that the response on the 3-month posttherapy PET was a surrogate for longer-term outcome."
The researchers have disclosed no relevant financial relationships.
Int J Radiat Oncol Biol Phys. Published online October?30, 2009.