Increase in Tumor Control and Normal Tissue Complication Probabilities in Advanced Head-and-Neck Cancer for Dose-Escalated Intensity-Modulated Photon and Proton Therapy

Abstract

IntroductionPresently used radiochemotherapy regimens result in moderate local control rates for patients with advanced head-and-neck squamous cell carcinoma (HNSCC). Dose escalation (DE) may be an option to improve patient outcome, but may also increase the risk of toxicities in healthy tissue. The presented treatment planning study evaluated the feasibility of two DE levels for advanced HNSCC patients, planned with either intensity-modulated photon therapy (IMXT) or proton therapy (IMPT).Materials and methodsFor 45 HNSCC patients, IMXT and IMPT treatment plans were created including DE via a simultaneous integrated boost (SIB) in the high-risk volume, while maintaining standard fractionation with 2 Gy per fraction in the remaining target volume. Two DE levels for the SIB were compared: 2.3 and 2.6 Gy. Treatment plan evaluation included assessment of tumor control probabilities (TCP) and normal tissue complication probabilities (NTCP).ResultsAn increase of approximately 10% in TCP was estimated between the DE levels. A pronounced high-dose rim surrounding the SIB volume was identified in IMXT treatment. Compared to IMPT, this extra dose slightly increased the TCP values and to a larger extent the NTCP values. For both modalities, the higher DE level led only to a small increase in NTCP values (mean differences <2%) in all models, except for the risk of aspiration, which increased on average by 8 and 6% with IMXT and IMPT, respectively, but showed a considerable patient dependence.ConclusionBoth DE levels appear applicable to patients with IMXT and IMPT since all calculated NTCP values, except for one, increased only little for the higher DE level. The estimated TCP increase is of relevant magnitude. The higher DE schedule needs to be investigated carefully in the setting of a prospective clinical trial, especially regarding toxicities caused by high local doses that lack a sound dose–response description, e.g., ulcers.

Intensity modulated proton therapy (IMPT) – The future of IMRT for head and neck cancer

“…82 Additional NTCP models are being investigated to estimate the efficacy of IMPT for specific HNCs sub-sites or when IMPT is delivered in a mixed modality treatment. 83–86…”

Potential proton and photon dose degradation in advanced head and neck cancer patients by intratherapy changes

“…Conformal dose distributions are typically provided by advanced photon therapy techniques like intensity‐modulated radiotherapy (IMRT) 1. While intensity‐modulated proton therapy (IMPT) can more effectively reduce the dose to healthy tissue2, 3, 4, 5 and thus allow for further dose escalation,6 proton beams are prone to range uncertainties if the penetrated tissue changes during therapy. Gradual intratherapy changes in HNC patient anatomy, mainly caused by weight loss, shrinkage of tumor, and shift of close‐by structures can be assessed via imaging, e.g.…”

NTCP modeling analysis of acute hematologic toxicity in whole pelvic radiation therapy for gynecologic malignancies – A dosimetric comparison of IMRT and spot-scanning proton therapy (SSPT)

“…To estimate and evaluate the effectiveness of PBT over photon therapy, several studies using the NTCP modeling analysis exist. Jakobi et al conducted in silico study using NTCP modeling analysis in head and neck region to identify patients who may benefit from PBT [31][32][33]. Makishima et al showed that NTCP value for the lung and heart decreased in proton plan compared with photon plan in esophageal cancer [34].…”