# Association between pelvic bone marrow dosimetry and acute hematologic toxicity during concurrent chemoradiotherapy for gynecologic malignancies

## TL;DR

This study shows that limiting radiation to pelvic bone marrow can reduce severe blood-related side effects in gynecologic cancer patients undergoing combined chemo and radiotherapy.

## Contribution

The study identifies specific bone marrow dose thresholds to mitigate acute hematologic toxicity in gynecologic malignancy patients.

## Key findings

- PBM-V15 above 80.44% is a strong predictor of grade ≥2 hematologic toxicity.
- LPBM-V5 above 91.25% specifically predicts grade ≥3 toxicity.
- Restricting these dose-volume parameters reduces toxicity risk without compromising treatment.

## Abstract

Pelvic radiotherapy for gynecologic malignancies damages the primary active bone marrow reservoir, inducing hematologic toxicity exacerbated by chemotherapy. Optimizing pelvic bone marrow dose–volume constraints is critical to mitigate myelosuppression and maintain treatment efficacy. The present retrospective cohort study analyzed patients with gynecological cancer (n = 61) undergoing concurrent chemoradiotherapy between August 2021 and August 2024. Associations between pelvic bone marrow (PBM) dose–volume parameters and acute hematologic toxicity (AHT) were systematically evaluated. All patients received intensity-modulated radiotherapy encompassing pelvic lymph node regions, with weekly complete blood count monitoring during and for 2 weeks after treatment. The overall incidence of AHT was 70.5% (43/61), with grade ≥ 2 and ≥ 3 AHT occurring in 63.9% (39/61) and 30.0% (14/61) of patients, respectively. Multivariate analysis identified PBM-V15 as an independent predictor of grade ≥ 2 AHT [odds ratio (OR), 2.653; 95% CI, 1.054–6.682; P = 0.038], with an optimal cutoff threshold of 80.44% [area under the curve (AUC), 0.854]. Notably, a lower PBM (LPBM)-V5 specifically predicted grade ≥ 3 AHT (OR, 1.425; 95% CI, 1.022–1.987; P = 0.037), with a threshold of 91.25% (AUC, 0.695). Implementing bone marrow-sparing strategies by restricting PBM-V15 to <80.44% significantly reduced the grade ≥ 2 AHT risk, while a stringent LPBM-V5 constraint (< 91.25%) was pivotal for preventing severe (grade ≥ 3) AHT. These dose–volume parameters should be incorporated into optimization protocols for pelvic radiotherapy in gynecological malignancies.