Estimation of Dose-Response Correlations Regarding Significant Blood Count Drops After Radiotherapy for Prostate Cancer

P. Papanikolaou, G. P. Swanson, S. Stathakis, M. Fakhreddine, P. Mavroidis

Research output: Contribution to journalArticlepeer-review

Abstract

PURPOSE/OBJECTIVE(S): It is accepted that radiation therapy can have some effect on hemoglobin/hematocrit, but it is not very well documented. The purpose of this study is to explore the effect of radiation monotherapy on hematocrit levels. MATERIALS/METHODS: Given that intensity modulated radiation therapy treats a large volume of normal tissue, we were concerned about the unrecognized effects of pelvic radiation therapy on blood counts. We prospectively obtained complete blood counts (CBCs) pretreatment, the end of treatment and 3 months post-RT from 2014-2016. With IRB approval we conducted a retrospective analysis of 221 patients treated with pelvic radiation for prostate adenocarcinoma. Given that the lifespan of RBCs is 120 days, we used the 3-month counts (approximately 130 days after 20 Gy is delivered). Dose volume histograms (DVHs) corresponding to 8 different contoured structures in the pelvis that were deemed significant in order to look for a correlation between pelvic structures and values of the CBC. These patients received either primary prostate radiation to 78 Gy total dose, or post-prostatectomy radiation for recurrence to 70 Gy total dose. Additionally, most of these patients had pelvic lymphatic irradiation (common iliac, external iliac, and internal iliac) to 54 Gy. Some patients received concomitant androgen ablation. RESULTS: Upon analysis, affected values were the RBC count, hemoglobin, and hematocrit. Hematocrit demonstrated the strongest correlation. Overall, the mean hematocrit dropped from 42.01% to 38.41% (8.57% decrease). Irradiated pelvic structures that correlated with significant decreases in hematocrit were the following: the bone volume of os coxae bilaterally superior to the acetabulum (OCUB), the entire os coxae bilaterally (OCTB), and the whole pelvis (BVWP). The OCUB showed the highest correlation, with a maximum AUC of 0.74 at V20 Gy with a volume threshold of 30%; odds ratio (OR) 9.8; confidence interval (CI) 2.9-32.9. Dose to the OCUB, showed an AUC of 0.73 with a dose of 23 Gy (OR 2.7, CI 1.3-5.6). For OCTB, maximum AUC of 0.69 was observed at V20 Gy where the volume threshold was 50%, (OR 9.3, CI 2.7-31.8). Mean dose analysis showed an AUC of 0.69 where the dose threshold was 28 Gy, odds ratio was 1.4 and CI 0.5-3.9 (not statistically significant). For BVWP a maximum AUC of 0.71 was seen at V20 Gy where the volume threshold was 40%, (OR 7.5, CI 2.2-25.4). Mean dose analysis showed an AUC of 0.72 where the dose threshold was 24 Gy, odds ratio was 2.6 and CI 1.1-6.1. CONCLUSION: These findings confirm the most radiosensitive sites of bone marrow in the pelvis. The doses to OCUB, OCTB and BVWP were found to correlate with a significant drop of hematocrit. A threshold of V20 Gy < 30% or mean dose < 23 Gy to OCUB may reduce almost ten-fold the risk for this endpoint.

Original languageEnglish (US)
Pages (from-to)e290
JournalInternational journal of radiation oncology, biology, physics
Volume111
Issue number3
DOIs
StatePublished - Nov 1 2021
Externally publishedYes

ASJC Scopus subject areas

  • Radiation
  • Oncology
  • Radiology Nuclear Medicine and imaging
  • Cancer Research

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