Stereotactic Pelvic Adjuvant Radiation Therapy as Potential Treatment for Uterine Cancer
—Results from a recent phase 1/2 prospective trial showed that stereotactic pelvic adjuvant radiation therapy for uterine cancer is well-tolerated and produced acceptable quality-of-life scores.
Minimizing patient burden and treatment costs makes the use of hypofractionated radiotherapy an attractive option for cancer treatment.1 However, little data on the use of hypofractionated radiotherapy for treating uterine cancer exist.
The phase 1/2 Stereotactic Pelvic Adjuvant Radiation Therapy in Cancers of the Uterus (SPARTACUS) included 61 patients (median age, 66 years [51-88]) with uterine cancer stages I through III who were treated with hypofractionated adjuvant pelvic radiation.2 This multicenter Canadian study was the first prospective trial in uterine cancer to assess treatment with hypofractionation. The primary end point of the study was acute bowel or urinary tract toxic effects. Patient-reported QOL, dosimetric feasibility, late toxic effects, pelvic control, and disease-free survival were all secondary endpoints.
Patients received 30 Gy in 5 fractions instead of the conventional treatment of 45 Gy in 25 fractions to achieve a comparable tumor control dose. A protocol amendment after the first 12 patients were treated was made to switch from once weekly to every other day treatment; this appeared to be well tolerated with toxicity profiles comparable to those of the first 12 patients who were treated once weekly. The median follow-up time was 9 months. A total of 39 patients had endometrioid adenocarcinoma, 15 had serous or clear cell, 3 carcinosarcoma, and 4 dedifferentiated. Sequential chemotherapy was administered to 16 patients, while nine patients received additional vault brachytherapy.
Among the 61 patients in the study, 33 (54%) and 8 (13%) experienced grade 1 and grade 2 worst acute GI tract toxic effects, respectively. Twenty-five patients (41%) and 2 patients (3%), respectively, experienced grade 1 and 2 genitourinary worst toxic effects. An acute grade 3 GI tract toxic effect of diarrhea at fraction occurred in one patient (1.6%), which resolved at follow-up. Compared with baseline, patient-reported diarrhea scores were both clinically (scores ≥10) and statistically significantly worse at fraction 5 (P<.001), but diarrhea scores improved at follow-up.2
Only one patient had biopsy-confirmed recurrent uterine cancer in the vagina at Fraction 5. The authors suggested this case may have been undetected, residual disease after surgery as no pelvic exam was noted for this patient at baseline assessment.2
Physician-assessed toxicities were reported as mostly grades 1 and 2 for gastrointestinal and genitourinary tracts. Only 1 patient experienced grade 3 gastrointestinal toxic effects, which were downgraded to grade 2 at the 6-week follow-up. These toxic effects resolved by 3 months.2
Acute hematologic toxic effects were reported for 31% as grade 1, 28% as grade 2, and 11% as grade 3. No grade 4 or higher effects were noted.2
The authors noted that the results of SPARTACUS were comparable to published data assessing treatments of endometrial cancer with conventional fractionation. The authors suggested that reducing the radiation treatment time from 35 days to 11 days by treating patients every other day may have benefits of minimizing breaks in chemotherapy. However, further long-term data are needed before this treatment strategy can be suggested to reduce patient and health care system burdens while maintaining efficacy that is comparable with the conventional radiation treatment strategies for uterine cancer.2
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