Adjuvant Treatment of Early Ovarian Clear Cell Carcinoma: A Population-Based Study of Whole Abdominal Versus Pelvic Nodal Radiotherapy

Authors: Soumyajit Roy MBBS 1 , 2 , 3 , Paul Hoskins MD, FRCPC 4 , 5 , Anna Tinker MD, FRCPC 4 , 5 , Harinder Brar MD 6 , 7 , Gale Bowering BS 1 and Gaurav Bahl MBBS, DNB, FRCPC 1 , 2
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  • 1 BC Cancer Agency, Abbotsford, British Columbia, Canada;
  • 2 Department of Surgery, University of British Columbia, Vancouver, British Columbia, Canada;
  • 3 Radiation Oncology Branch, National Cancer Institute, National Institutes of Health, Bethesda, Maryland; and
  • 4 BC Cancer Agency,
  • 5 Department of Medicine, University of British Columbia,
  • 6 Vancouver General Hospital, and
  • 7 Department of Obstetrics & Gynecology, University of British Columbia, Vancouver, British Columbia, Canada.
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Background: Adjuvant treatment in early ovarian clear cell carcinoma (OCCC) is not yet standardized. The objective of this population-based study was to compare the outcome of patients with early OCCC treated with adjuvant chemotherapy versus chemoradiotherapy (chemoRT) and evaluate the association of adjuvant radiotherapy regimens (whole abdominal radiotherapy [WART] versus pelvic nodal radiotherapy [PRT]) with outcome. Patients and Methods: Chart review was conducted to identify patients with stage I and II OCCC with complete information on staging. Patients with stage IA, IB, or IC OCCC purely resulting from capsular rupture were excluded because the provincial protocol does not recommend adjuvant treatment. Results: Overall, 403 patients were identified and 343 received adjuvant treatment, of whom 255 had stage IC or II OCCC and 153 were eligible for final analysis. On Cox multivariable regression, receipt of chemoRT (n=90) was associated with an improvement in failure-free survival (FFS) (hazard ratio [HR], 0.57; 95% CI, 0.34–0.94) compared with chemotherapy alone (n=63). Use of chemoRT also resulted in 54% reduction in the cumulative incidence of cancer-specific mortality (subdistribution HR, 0.46; 95% CI, 0.24–0.89). However, there was no significant difference in the HR for overall survival (OS) between the chemoRT (HR, 0.70; 95% CI, 0.43–1.13) and chemotherapy group. Relative to chemotherapy + WART (chemo-WART), chemotherapy + PRT (chemo-PRT) was not associated with any significant difference in HR for FFS (HR, 1.34; 95% CI, 0.40–4.44) or OS (HR, 1.13; 95% CI, 0.37–3.46). Conclusions: Adjuvant chemoRT was associated with a lower risk of failure compared with chemotherapy alone. However, there was no difference in OS between the adjuvant chemotherapy and chemoRT regimens. Additionally, no significant difference in terms of FFS or OS was found between the chemo-WART and chemo-PRT groups.

Submitted March 5, 2020; accepted for publication June 26, 2020. Published online September 24, 2020.

Previous presentation: Part of this study was presented as an oral presentation at the 59th Annual Meeting of American Society for Radiation Oncology; September 24–27, 2017; San Diego, California (Int J Radiat Oncol Biol Phys 2017;99:S110–111).

Author contributions: Study concept and design: Roy, Bahl. Provision of study material or patients: Roy, Hoskins, Tinker, Bahl. Administrative support: Bowering. Data collection and assembly: Roy, Bowering. Data analysis and interpretation: Roy, Hoskins, Bahl. Manuscript writing: All authors. Final approval of manuscript: All authors.

Disclosures: Dr. Bahl has disclosed that he receives honoraria from Bayer, Janssen, and Sanofi. The remaining authors have disclosed that they have no financial interests, arrangements, affiliations, or commercial interests with the manufacturers of any products discussed in this article or their competitors.

Funding: This project was supported by Radiotherapy Education Process Fund, BC Cancer Agency, Abbotsford, British Columbia, Canada.

Correspondence: Gaurav Bahl, MBBS, DNB, FRCPC, Department of Radiation Oncology, BC Cancer Agency, 32900 Marshall Road, Abbotsford, British Columbia, V2S 0C2, Canada. Email: Gaurav.bahl@bccancer.bc.ca

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