Correlation between radiation dose to bone marrow subregions and acute hematologic toxicity inendometrial cancer treated with external beam radiotherapy

Abstract

Aim

To identify dosimetric parameters associated with acute hematologic toxicity (HT) in endometrial cancer treated with volumetric modulated arc therapy (VMAT-RT).

Methods

Patients with uterine adenocarcinoma treated in our Institution from March 2019 to November 2022 were retrospectively enrolled in this study. All patients underwent adjuvant external beam radiotherapy with Volumetric modulated arc therapy (VMAT) strategy plus a brachytherapy boost on vaginal cuff. When indicated, adjuvant platin-based chemotherapy was administered after surgery in upfront or sandwich setting. Pelvic bone marrow was contoured for each patient and divided into three subsites: lumbosacral spine (LSBM), ilium (IBM) and lower pelvis (LPBM). The volume of each region receiving 10,20,30 and 40 Gy (V10, V20, V30, V40, respectively) and mean dose (Dmean) was collected. Hematological toxicity during radiotherapy treatment was graded according to the CTCAE V 5.0. Linear logistic regression models were used to test associations between dosimetric parameters and HT.

Results

Data from 99 patients were retrospectively analyzed. Adjuvant external beam radiotherapy was delivered to the pelvis with Volumetric modulated arc therapy (VAMT) strategy for a total dose of 45  Gy, 1.8  Gy/fraction plus a brachytherapy boost on vaginal cuff for a total dose of 10 Gy in 2 fractions weekly. Thirty-one patients developed during radiotherapy treatment an HT ≥ grade 2.

With a sensitivity of 83.3 % and specificity of 61.5 %, V20 Gy LSBM < 64 % is associated to a maximum 20 % risk of Grade 2 or worse HT in patients with < 60 years old; for patients older than 70, the risk of toxicity is below 20 % independently by the percentage volume of V20Gy LSBM (95 % CI 0.60–0.87; p = 0.03).

No association between hematological toxicity and V10-20–30-40 or Dmean of IBM and LPBM were observed.

Dosimetric parameters involving the lower pelvis had stronger association with hematological toxicity than those involving the ilium, even if not significant.

Conclusions

In this experience a dose constraint age-dependent was proposed, to reduce the risk of HT.

The volume of lombo-sacral pelvis receiving low-dose radiation (V20 LSBM > 64 %) seems to be associated with HT in younger patients; instead in older than 70 patients the percentage of V20Gy LSBM seems not correlate with risk of toxicity. Future investigations should seek to confirm these findings through the inclusion of these parameters in the planning process.