The baseline volume of ABM and the fraction of ABM present in patients vary significantly. The ongoing NRG-GY006 trial and other efforts at bone marrow sparing use V10, V20, and mean dose to the ABM during planning optimization. This analysis suggests that the volume of ABM spared 40 Gy (> 738 cc) may be a stronger predictor of HT than conventional dosimetric parameters. This should be further evaluated for clinical use.

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Purpose: Magnetic resonance imaging (MRI)-guided adaptive brachytherapy is the standard of care for cervical cancer. Hybrid intracavitary/interstitial applicators for bulky tumor (high-risk clinical target volume [HR-CTV] > 30 cc) dose escalation is recommended in the EMBRACE II trial. The value of hybrid applicators for smaller HR-CTV (< 30 cc) in organ at risk (OAR) sparing is less certain. Material and methods: Twenty-seven patients with FIGO stage I-IVA cervical cancer treated with definitive chemoradiation and MRI-based brachytherapy using conventional tandem and ring (TR) applicators were re-planned using virtual needles. They were then summed with the external beam dose to evaluate target coverage and OAR dose using EQD 2 summation. Target and OAR dose with/without hybrid applicator use were compared. Results: Eighty-one percent had HR-CTV volumes < 30 cc, for which, hybrid TR applicators had significantly lower mean D 2cc to all OARs without differences in target coverage. For HR-CTV < 30 cc, the bladder and rectal OAR goals per EMBRACE II were exceeded in significantly fewer patients with the hybrid TR applicators. No significant difference was found in the sigmoid D 2cc dose goal. Conclusions: In small volume tumors (< 30 cc), hybrid applicators may offer improved OAR sparing compared with conventional tandem and ring applicators, and may increase the proportion of patients meeting EMBRACE II OAR goals.

Kharofa (2018) The volume of PET-defined, active bone marrow spared predicts acute hematologic toxicities in anal cancer patients receiving concurrent chemoradiotherapy,

ObjectiveThe objectives of this study were to evaluate whether dose to the vasculature is associated with local control after surgery in patients with borderline resectable (BLR) and resectable pancreatic cancer (PCA) receiving neoadjuvant radiation therapy (RT) and to identify a dose threshold for clinical use.MethodsPatients with BLR and resectable PCA treated with neoadjuvant RT were retrospectively reviewed. During this period, the institutional paradigm shifted from standard fractionation to hypofractionation/stereotactic body radiation therapy (SBRT). A vasculature clinical target volume (Vasc CTV) was contoured for each patient and defined as a 5-mm margin around the superior mesenteric artery (SMA) from its origin to the pancreatic head, the celiac artery from its origin to the level of the trifurcation and any involved vein. The Vasc CTV D95 was normalized to a 2-Gy equivalent dose to determine the optimal dose associated with optimal local failure-free survival (LFFS).ResultsForty-seven patients were included in the analysis. A Vasc CTV D95 of 32.7 Gy was the optimal cutoff for LFFS. Patients with Vasc CTV D95 Equivalent dose in 2 Gy per fraction (EQD2) &gt;32.7 Gy had significantly longer LFFS compared to patients with Vasc CTV D95 EQD2 ≤32.7 Gy at 12 months (91% vs. 51%, respectively) and 24 months (86% vs. 12%, respectively). The median disease-free survival (DFS) for patients with EQD2 &gt;32.7 Gy was 30.4 months compared to 14.0 months in patients with EQD2 ≤32.7 Gy (p = 0.01). There was no significant difference in overall survival (OS) between the two groups.ConclusionsDuring neoadjuvant treatment, dose to the Vasc CTV is associated with durability of local control (LC) after resection and should be intentionally included in the treatment volume with an EQD2 goal of 31–33 Gy.

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identified on PET/CT. Lymph nodes were delineated on patient planning CT scans, and measurements taken from the volumetric center of the lymph node to the major vessels. Expansions of the major vessels were applied to create a clinical target volume (CTV). Initially, the vessels were expanded by the mean distances from the great vessels to the lymph node center. Expansion margins were then increased to produce a number of iterations until a clinically acceptable lymph node coverage was obtained. These expansions were then validated on a further 10 patients with 29 para-aortic lymph nodes. Using these expansion margins, a detailed guide and accompanying visual atlas for elective para-aortic node CTV delineation was created. Results: The mean distance from the center of the node to the aorta was 8mm (range 4-17mm) for both left lateral para-aortic and aorto-caval nodes. The mean distance from the IVC to the center of the right paracaval nodes was 5mm (range 4mm-6mm) and to the center of the aortocaval nodes was 6mm (range 3-15mm). The most superior lymph node was at the level of the L1 vertebra. Although the location of the left renal vein in relation to skeletal anatomy varied between patients, all lymph nodes were inferior to the level of the left renal vein. The most inferior lymph node was at the level of L5 vertebra, with no lymph nodes below the level of the bifurcation of the aorta. A CTV expansion from the aorta of 10mm circumferentially and 15mm laterally, and from the IVC of 8mm anteriorly/medially and 6mm posteriorly/laterally resulted in 97% para-aortic node coverage (38/39 nodes) in the design cohort. On prospective validation of these expansion margins the result was coverage of 97% (28/29) of para-aortic lymph nodes. Conclusion: We have shown that an asymmetrical margin based on the likely distribution of the para-aortic lymph nodes allows for accurate CTV delineation while sparing normal surrounding tissues. We have also provided a detailed guide, and accompanying visual atlas, to aid in para-aortic CTV delineation in cervical cancer.