Background and purpose: To determine if suppression of active bone marrow, as defined on FDG PETCT, is seen in on-treatment imaging of anal cancer patients receiving concurrent chemoradiation.
Methods and materials: Scans from 26 patients participating in the ART trial (full title: Anal squamous cell carcinoma: Investigation of functional imaging during chemoRadioTherapy), a single center observational study with FDG PETCT prior to radiotherapy and at fraction 8-10 of concurrent chemoradiation were analysed. Active bone marrow was contoured in both the pelvis and un-irradiated thoracic spine. SUV and volume of active bone marrow after 8-10 fractions of treatment were compared to baseline. Dose metrics to pelvic active bone marrow were extracted and compared to reduction in SUV/active bone marrow volume and to blood count nadir using linear regression.
Results: Suppression of active bone marrow is seen in the pelvis by a reduction in mean SUV and volume of active bone marrow after 8-10 fractions of treatment. Suppression is not seen in un-irradiated thoracic spine. Dose metrics were associated with reduced SUV and reduced volume of active bone marrow. Volume of active bone marrow receiving <20 Gy was associated with WCC/ANC nadir. 20 Gy was identified as the most likely clinically meaningful dose threshold for toxicity. Volume of active bone marrow receiving <20 Gy correlated to WCC and ANC with an increase of 100 cc being associated with an increase of 0.4 and 0.3 respectively.
Conclusion: The effect of concurrent chemoradiation in suppression of active bone marrow is seen in on-treatment FDG PETCT scans. Chemotherapy appears well tolerated after 2 weeks of treatment.
Trial registration: ClinicalTrials.gov NCT02145416.
Keywords: Haematological toxicity; Intensity modulated radiotherapy; Pelvic bone marrow; Positron-emission tomography.
Copyright © 2019 The Authors. Published by Elsevier B.V. All rights reserved.