The prognostic effect of tumor volume, reduction ratio, and cumulative doses on external beam radiotherapy with central-shielding method and image-guided adaptive brachytherapy for cervical cancer

Takeru Ohtaka; Ken Ando; Takahiro Oike; Shin-Ei Noda; Takuya Kaminuma; Kazutoshi Murata; Tatsuya Ohno

doi:10.3389/fonc.2024.1366777

The prognostic effect of tumor volume, reduction ratio, and cumulative doses on external beam radiotherapy with central-shielding method and image-guided adaptive brachytherapy for cervical cancer

Front Oncol. 2024 May 7:14:1366777. doi: 10.3389/fonc.2024.1366777. eCollection 2024.

Authors

Takeru Ohtaka¹, Ken Ando¹, Takahiro Oike^{1

2}, Shin-Ei Noda³, Takuya Kaminuma⁴, Kazutoshi Murata⁵, Tatsuya Ohno^{1

2}

Affiliations

¹ Department of Radiation Oncology, Gunma University Graduate School of Medicine, Maebashi, Japan.
² Gunma University Heavy Ion Medical Center, Maebashi, Japan.
³ Department of Radiation Oncology, Saitama Medical University International Medical Center, Hidaka, Japan.
⁴ Department of Radiation Therapy, NHO Shibukawa Medical Center, Shibukawa, Japan.
⁵ QST Hospital, National Institutes for Quantum and Radiological Science and Technology, Chiba, Japan.

Abstract

Objective: To evaluate the prognostic effect of tumor volume at diagnosis, tumor reduction ratio during external beam radiotherapy (EBRT) with central-shielding method, and cumulative minimal dose to 90% of the high-risk clinical target volume (CTV_HR D₉₀) on combined EBRT and image-guided adaptive brachytherapy (IGABT) for cervical cancer.

Methods: Consecutive patients who underwent definitive radiotherapy or concurrent chemoradiotherapy for cervical cancer at Gunma University Hospital between January 2010 and December 2019 were retrospectively reviewed. Tumor volume at diagnosis and reduction ratio were calculated using magnetic resonance imaging at diagnosis and before the first IGABT session. The cumulative dose of EBRT and IGABT was calculated as an equivalent dose in 2 Gy fractions (EQD2). Optimal cutoff values were determined according to a receiver operating characteristic curve. Treatment outcomes were evaluated using the Kaplan-Meier method and compared using the log-rank test and Cox proportional hazards regression.

Results: A total of 254 patients were included in the analysis. The median follow-up for all patients was 57 (2-134) months. The 5-year overall survival (OS) was 81.9%, progression-free survival (PFS) was 71.3%, and local control (LC) was 94.5%. The patients were divided into four groups according to tumor volume at diagnosis and reduction ratio. The group with tumor volume at diagnosis ≥ 34.1 cm³ and reduction ratio < 68.8% showed significantly worse OS, PFS, and LC than the other three groups (All p < 0.05). In this group, the patients with a cumulative CTV_HR D₉₀ < 69.6 Gy_EQD2 showed significantly worse PFS and LC (p = 0.042 and p = 0.027, respectively). In the multivariate analysis of OS, adenocarcinoma/adenosquamous carcinoma, International Federation of Gynecology and Obstetrics 2009 stage III/IV, and a reduction ratio of < 68.8% were independent significant poor prognostic factors (p = 0.045, p = 0.009 and p = 0.001, respectively). In the univariate analysis of LC, a reduction ratio of < 68.8% was the only poor prognostic factor (p = 0.041).

Conclusion: The patients with large and poorly responding tumors had significantly worse prognoses in terms of OS, PFS, and LC, suggesting that dose escalation should be considered for such tumors.

Keywords: brachytherapy; cervical cancer; cumulative doses; prognosis; radiotherapy; reduction ratio; tumor volume.

Grants and funding

The author(s) declare financial support was received for the research, authorship, and/or publication of this article. This research was supported by Gunma University Heavy Ion Medical Center.