2859 - Ovarian Function Preservation after Postoperative Radiotherapy for Cervical Cancer Patients Who Underwent Ovarian Transposition: A Comparison of IMRT and 3D-CRT

Purpose/Objective(s): This study aims to evaluate the impact of postoperative pelvic radiotherapy (PORT) on ovarian function in premenopausal cervical cancer patients who have undergone ovarian transposition. Given the increasing use of intensity-modulated radiation therapy (IMRT) for PORT, the study specifically investigates whether IMRT can effectively preserve ovarian function despite the potential for low-dose irradiation to the transposed ovary. Additionally, it seeks to identify risk factors affecting ovarian function and establish ovarian dose constraint criteria.

Materials/Methods: Twenty-two premenopausal cervical cancer patients underwent PORT with intent to reduce to minimize ovarian dose after radical hysterectomy and ovarian transposition at our institution between 2007 and 2021. Ages ranged from 26 to 43 years (median 35). PORT was performed using 3D-CRT in 8 cases and IMRT in 14 cases. Pre-PORT FSH levels ranged from 1.8 to 9.0 mIU/ml (median 4.9). The total dose was 50.4 Gy/28 fractions, except for one case (45 Gy/25fr). Ovaries were shielded with AP-PA fields in 3D-CRT, while IMRT optimized to minimize ovarian dose. The study analyzed the incidence of premature ovarian insufficiency (POI) requiring estrogen replacement therapy (ERT) and examined clinical and dosimetric risk factors.

Results: The follow-up period ranged from 38 to 181 months (median 88), with no cases of relapse or death observed. Transient POI was observed in 12 of 22 patients (73%), but five recovered spontaneously, allowing ERT discontinuation. This resulted in a final persistent POI rate of 11 out of 22 (50%). According to irradiation method, transient POI occurred significantly more frequently with IMRT than with 3D-CRT (100% vs. 25%, p<0.001), while persistent POI was higher with IMRT (64% vs. 25%) but without statistical significance (p=0.076). Both mean ovarian dose and V5Gy of ovaries were significantly lower with 3D-CRT. In multivariate analysis, IMRT was a significant factor for transient POI (p=0.018), while Dmax >5.8 Gy of the lower dose-side ovary was significantly associated with persistent POI (p=0.050).

Conclusion: The incidence of persistent POI was 50% even after ovarian transposition. IMRT was associated with higher rate of POI compared to 3D-CRT, suggesting a low-dose effect on the transposed ovaries. If ovarian function preservation is the priority, 3D-CRT is more reliable than IMRT. However, IMRT could be selected due to its benefits in reducing other late adverse events, such as bowel toxicities. In such cases, it is important to minimize ovarian dose—particularly keeping the maximum dose to the lower dose-side ovary below 5.8 Gy—to improve the likelihood of ovarian function preservation.