ESTRO 2024 - Abstract Book

S1121

Clinical - Gynaecology

ESTRO 2024

2 Lorusso D, et al. Pembrolizumab plus chemoradiotherapy for high-risk locally advanced cervical cancer: A randomized double-blind, phase 3 ENGOT-cx11/GOG-3047/KEYNOTE-A18 study. ESMO Congress 2023, LBA38.

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Bone marrow exposure and haematological toxicity in pelvic VMAT concurrent chemo-radiotherapy

Amal Riahi, Zeineb Naimi, Meriem Bohli, Raouia Ben Amor, Awatef Hamdoun, Ghada Bouguerra, Rihab Haddad, Lotfi Kochbati

Abderrahmen Mami Hospital Ariana, Radiation Oncology Department, Ariana, Tunisia

Purpose/Objective:

This study aimed to evaluate radiation dose distribution to pelvic bone marrow (BM) in VMAT radiotherapy for gynaecologic cancer patients treated with concurrent chemo-radiation and to analyse correlation between pelvic BM dosimetry metrics and acute haematological toxicity.

Material/Methods:

All gynaecologic cancer patients treated with VMAT radiotherapy and concurrent chemotherapy at our institution in 2023, were included in this study. Haematological parameters were collected from complete blood count (CBC) at baseline and at the 5th week of concurrent treatment. For each blood cell line, we calculated the difference between pre-treatment and 5th week count (delta). Pelvic BM was retrospectively delineated including iliac crests, lower pelvis and lumbosacral region. Dose volume histograms were generated and the following dosimetry metrics to BM were assessed: Dmean, V5Gy, V10Gy, V20Gy, V30Gy and V40Gy. Statistical association between dosimetry metrics to BM and delta CBC were analysed using the Pearson correlation coefficient and the linear regression analysis.

Results:

A total of 31 eligible patients were included in this study. Two patients were excluded from analysis for concurrent chemotherapy unfitness. The mean age was 61 years old. The study cohort included 51.7% of endometrial cancer patients, 41.3% of cervical cancer patients and 7% of vulvar cancer patients. Adenocarcinoma and squamous cell carcinoma were the main histological subtypes. Statistically significant positive correlation was found between delta white blood cells (WBC), platelets (PLT) and neutrophils (PNN) and all BM dosimetry metrics, with Pearson coefficients ranging between 0.39 and 0.76 (p≤0.03). The strongest correlation was found between V30 Gy(BM) and delta(PLT) with Pearson coefficient of 0.76 (p<0.0001). V30Gy (BM) had a strong predictive value of PLT, PNN and WBC decrease at the 5th week of concurrent chemo-radiotherapy with r²≥0.5. V40Gy (BM) and Dmean (BM) showed similar predictive values with r² ranging between 0.31 and 0.52. Dosimetry metrics to BM did not statistically correlate with delta haemoglobin neither delta lymphocyte.

Conclusion: