The ratio of weight loss to planning target volume significantly impacts setup errors in nasopharyngeal cancer patients undergoing helical tomotherapy with daily megavoltage computed tomography

Abstract

BackgroundChanges in head and neck anatomy during radiation therapy (RT) produce setup uncertainties of nasopharyngeal cancer (NPC) irradiation. We retrospectively analyzed image guidance data to identify clinical predictors of setup errors.Patients and methodsThe data of 217 NPC patients undergoing definitive RT on a helical tomotherapy (HT) unit were analyzed. Factors including tumor stage, body mass index, weight loss, and planning target volume (PTV) were assessed as predictors of daily megavoltage computed tomography (MVCT) setup displacements, which were automatically registered using software.ResultsMean daily setup displacements (in mm) were 1.2 ± 0.6, 1.8 ± 0.8, 3.4 ± 1.4 in the medial-lateral (ML), superior-inferior (SI), and anterior-posterior (AP) directions, respectively. Mean weight loss was 4.6 ± 3.3 kg (6.8 ± 4.9%). Patients with weight loss > 5% had significantly larger setup displacements in the AP (3.6 ± 1.5 vs. 2.9 ± 1.1 mm, p < 0.001) and SI (1.6 ± 0.7 vs. 1.9 ± 0.9 mm, p = 0.01) direction, but not in the ML direction (p = 0.279). The AP setup error increased 0.06 mm (y = 0.055x + 2.927, x: percentage of weight loss/PTV, y: AP displacement) per one percent increase in weight loss normalized to PTV.ConclusionsPatients with weight loss > 5% and smaller PTVs, possibly because of small body frame or neck girth, were more likely to have increased setup errors in the AP direction.

Radiotherapy for Head and Neck Cancer: Evaluation of Triggered Adaptive Replanning in Routine Practice

“…All three cases received chemotherapy in addition to radiotherapy (2 had cisplatin 100 mg/m 2 and 1 had carboplatin with previous induction chemotherapy). The mean fraction for rescan CT was 21 (range, [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29]. No other primaries were found to be correlated with need for ART ( Table 3).…”

“…The literature provides contradictory data about the correlation of weight loss and the necessity for ART. Wei-Hsien Hou et al found that NPC patients with weight loss > 5% and smaller PTVs were more likely to have increased setup errors (28). Mahmoud et al found weight loss of more than 9.6% as the critical value to trigger ART in terms of target under dosing and/or spinal cord/parotids overdosing (29).…”

Practical Aspects of the Application of Helical Tomotherapy for Craniospinal Irradiation

“…Several studies have reported that weight loss affects interfractional set up errors 34,35 , but there is no report on intrafractional movement. The association between weight loss and intrafractional movement in our study can be discussed in terms of the following two aspects: rst, due to toxicity or nausea induced by a high radiation dose during RT, the patient's appetite deteriorates, leading to a poor condition; therefore, the weight decreases with progression of the treatment.…”

Prospective assessment of inter- or intra-fractional variation according to body weight or volume change in patients with head and neck cancer undergoing radiotherapy

“…The correlations between ΔBW and Δ(inter) were significant in several studies [23,24], although some studies reported contrasting results [25,26]. Hou et al [23] reported that patients with nasopharyngeal cancer with weight loss of >5% had significantly larger ΔAP(inter). Zia et al [24] found that weight loss was associated with ΔLR(inter).…”