Main Session
Sep
29
PQA 07 - Head and Neck Cancer, Lung Cancer/Thoracic Malignancies, and Nursing and Supportive Care
3414 - Evaluation of Dosimetric Parameters in Patients with Head and Neck Cancer Undergoing Hypofractionated Adjuvant Radiotherapy: An Ancillary Study of HART-HN
Presenter(s)
Lou-Anne Acevedo-Moreno, MD - Medical College of Wisconsin, Milwaukee, WI
L. A. Acevedo-Moreno1, J. Zenga2, E. S. Paulson1, M. E. Shukla1, S. Firat3, S. Wong4, A. Memon5, T. Matoska1, B. Campbell3, K. Akakpo3, B. Massey3, J. D. Bruening3, M. Stadler3, M. Agarwal3, S. Tarima6, A. Banerjee7, C. J. Schultz3, and M. J. Awan1; 1Department of Radiation Oncology, Medical College of Wisconsin, Milwaukee, WI, 2Medical College of Wisconsin, Milwaukee, WI, United States, 3Medical College of Wisconsin, Milwaukee, WI, 4Department of Medical Oncology, Medical College of Wisconsin, Milwaukee, WI, 5Department of Otolaryngology and Communication Sciences, Medical College of Wisconsin, Milwaukee, WI, 6University of Kentucky, Lexington, KY, 7Department of Biostatistics, Medical College of Wisconsin, Milwaukee, WI
Purpose/Objective(s):
Conventionally fractionated postoperative radiotherapy (PORT) for head and neck cancer (HNC) is delivered over approximately 6 weeks and is associated with substantial acute toxicity, particularly when combined with systemic therapy. Hypofractionation offers the potential to shorten treatment duration, improve PORT completion rates, and delay acute toxicity. We performed a dosimetric analysis of patients enrolled on the Phase I HART-HN (Hypofractionated Adjuvant Radiotherapy for Resected Head and Neck Cancers) trial to determine whether hypofractionated adjuvant radiotherapy achieves target coverage while maintaining organ-at-risk (OAR) constraints.Materials/Methods:
Seventeen patients with resected HNC treated on the IRB-approved HART-HN study were included. Patients received 42 Gy in 10 fractions, 39 Gy in 10 fractions, or 32.5 Gy in 5 fractions. Standardized workflows in MIM Software generated conformity indices (CI), homogeneity indices (HI), and OAR dose metrics. For the high-dose planning target volume (PTV High), CI and HI evaluated prescription isodose conformality and dose uniformity. Conformity of the combined PTV (union of high- and low-dose volumes) was calculated relative to the lower prescription isodose to assess geometric containment of the total treated volume and low-dose spillage. Combined-volume conformity was interpreted strictly as a geometric metric rather than a measure of high-dose plan quality. OAR metrics included spinal cord and brainstem D0.03cc and esophageal mean dose.Results:
Seventeen patients were treated with 32.5 Gy (n=10), 39 Gy (n=4), or 42 Gy (n=3). Geometric plan quality was maintained across regimens. For the high-dose PTV, median CI was 0.995 (IQR, 0.930–1.018), 1.040 (1.002–1.080), and 0.930 (0.915–0.945) for the 32.5 Gy, 39 Gy, and 42 Gy regimens, respectively. Median HI values were 0.075 (0.070–0.090), 0.075 (0.068–0.085), and 0.090 (0.090–0.100). Combined-PTV CI values were 0.700 (0.542–0.815), 0.590 (0.505–0.760), and 0.620 (0.585–0.695), respectively. All evaluated OAR doses remained within protocol-specified constraints. Median spinal cord D0.03cc doses were 1493.5 cGy (1360.5–1640.0), 1592.5 cGy (1492.3–1748.5), and 2381.0 cGy (1957.0–2408.5). Median brainstem D0.03cc doses were 1088.5 cGy (820.8–1270.8), 1727.0 cGy (1514.5–1759.5), and 1756.0 cGy (1614.5–2011.0). Median esophageal mean doses were 1333.0 cGy (1213.3–1407.0), 1851.0 cGy (1816.5–1874.0), and 1941.0 cGy (1860.0–2125.0), respectively. Clinical outcomes will be reported separately.Conclusion:
In this ancillary analysis of HART-HN, hypofractionated adjuvant radiotherapy achieved highly conformal, homogeneous target coverage across dose levels while maintaining strict adherence to normal tissue constraints. These data demonstrate that treatment acceleration can be accomplished without degradation of dosimetric quality and support continued clinical evaluation of hypofractionated adjuvant strategies in HNC.