How should we appropriately classify low-risk uterine cervical cancer patients suitable for de-intensified treatment?

Role of the gel spacer in safely delivering whole pelvic radiation therapy without central shielding in computed tomography-based image-guided adaptive brachytherapy for uterine cervical cancer patients

BACKGROUND

To protect the rectum and bladder from high dose exposure, the Japanese guidelines for managing uterine cervical carcinoma recommend pelvic irradiation with central shielding (CS). Conversely, the European Society for Radiotherapy and Oncology (ESTRO) and the American Brachytherapy Society (ABS) guidelines recommend delivering ≥85 Gy to high-risk clinical target volume D90 (CTVHR D90%). In this study, we investigated whether a gel spacer can enable the safe delivery of the ESTRO/ABS-recommended doses to the target while observing dose constraints for the OARs without using CS in external beam radiation therapy (EBRT).

MATERIALS AND METHODS

Twenty patients who received definitive radiation therapy without CS and were treated by brachytherapy with a gel spacer between 2017 and 2022 were retrospectively reviewed. The cumulative doses of EBRT and brachytherapy treatment outcomes and incidence of adverse events were also examined.

RESULTS

The median cumulative CTVHR D90%, rectum D2cm3, and bladder D2cm3 were 86.6 Gy, 62.9 Gy, and 72.0 Gy, respectively. The 2-year local control rate was 95%. There were no CTCAE ≥Grade 3 late gastrointestinal or genitourinary adverse events.

CONCLUSIONS

The use of gel spacer can enable ESTRO/ABS-recommended dose constraints even without using CS in EBRT, with favorable outcomes and low adverse event rates.

Is it time to modify the Japanese Uterine Cervical Cancer Guidelines to recommend a higher dose for radio-resistant tumors?

Compared with the European or the United States' uterine cervical cancer management guidelines, which aim to deliver >85 Gy EQD2 (the equivalent effective dose in 2 Gy per fraction) to the high-risk clinical target volume (CTVHR) D90 (minimal dose of 90% of the CTVHR), the dose goal of the corresponding Japanese guidelines does not recommend delivering such a high dose to the CTVHR D90. Subsequently, while the rate of late radiation-induced toxicities is reported to be much lower in the Japanese schedule, the local control rate is relatively inferior to that of clinical results reported by the IntErnational study on MRI-guided BRAchytherapy in CErvical cancer study (EMBRACE-I) in which the dose goal for CTVHR D90 was >85 Gy and showed >90% local control regardless of tumor stage. In daily clinical practice, patients with residual disease supposedly due to insufficient total dose delivery are occasionally referred to our hospital for the possibility of re-irradiation, which is not usually recommended because the risk of late severe radiation-induced toxicity is high. In this report, the authors hope to raise a discussion in our community about modifying our treatment guidelines to recommend a higher dose at least for patients with poor response.