I am SPARTACUS.

Top Line: Hypofractionation hasn’t made much headway in the management of gynecologic cancers with external beam radiation.

The Study: Both rectal cancer and prostate cancers have well-established 5-fraction whole pelvis regimens, so what’s the hold up in the post-hysterectomy setting? The phase 1/2 Stereotactic Pelvic Adjuvant Radiation Therapy in Cancers of the Uterus (SPARTACUS) trial—some people were just born to acronymize—evaluated adjuvant pelvic radiation of 30 Gy in 5 fractions administered every other day or once weekly for 61 patients following hysterectomy for stage I-III uterine cancer. Interestingly, this dose is higher than the aforementioned regimens (25 Gy), but the same dose constraints to organs at risk were used. While the goal was to have 95% of the target receiving 30 Gy, 95% receiving 27.5 Gy was acceptable if necessary to meet bowel constraints. If even this wasn’t achievable, the patient received standard fractionation. All patients were treated with VMAT using RTOG volumes on a couch with 6-degrees-of-freedom and daily cone beam CT-alignment. The primary outcome was GI and GU toxicity rates, which would be deemed acceptable if less than 5 patients experienced a grade 3+ toxicity. Grade 1 and 2 GI / GU toxicity occurred in 54 / 41% and 13 / 3% patients, respectively. One patient had grade 3 diarrhea for a few weeks upon completion of radiation. Diarrhea during this time period was the stand-out detriment to quality of life, though again it resolved by week 6.

TBL: This early phase trial suggest favorable toxicity with 5-fraction adjuvant pelvic radiation for endometrial cancer. | Leung, JAMA Oncol 2022