Recurrence Patterns After IMRT/VMAT in Head and Neck Cancer

Abstract

Purpose: Intensity-modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT), two advanced modes of high-precision radiotherapy (RT), have become standard of care in the treatment of head and neck cancer. The development in RT techniques has markedly increased the complexity of target volume definition and accurate treatment delivery. The aim of this study was to indirectly investigate the quality of current TV delineation and RT delivery by analyzing the patterns of treatment failure for head and neck cancer patients in our high-volume RT center.

Methods: Between 2004 and 2014, 385 patients with pharyngeal, laryngeal, and oral cavity tumors were curatively treated with primary RT (IMRT/VMAT). We retrospectively investigated locoregional recurrences (LRR), distant metastases (DM), and overall survival (OS).

Results: Median follow-up was 6.4 years (IQR 4.7-8.3 years) during which time 122 patients (31.7%) developed LRR (22.1%) and DM (17.7%). The estimated 2- and 5-year locoregional control was 78.2% (95% CI 73.3, 82.3) and 74.2% (95% CI 69.0, 78.8). One patient developed a local recurrence outside the high-dose volume and five patients developed a regional recurrence outside the high-dose volume. Four patients (1.0%) suffered a recurrence in the electively irradiated neck and two patients had a recurrence outside the electively irradiated neck. No marginal failures were observed. The estimated 2- and 5-year DM-free survival rates were 83.3% (95% CI 78.9, 86.9) and 80.0% (95% CI 75.2, 84.0). The estimated 2- and 5-year OS rates were 73.6% (95% CI 68.9, 77.8) and 52. 6% (95% CI 47.3, 57.6). Median OS was 5.5 years (95% CI 4.5, 6.7).

Conclusion: Target volume definition and treatment delivery were performed accurately, as only few recurrences occurred outside the high-dose regions and no marginal failures were observed. Research on dose intensification and identification of high-risk subvolumes might decrease the risk of locoregional relapses. The results of this study may serve as reference data for comparison with future studies, such as dose escalation or proton therapy trials.

Keywords: delineation; head and neck cancer; intensity-modulated radiotherapy; proton therapy; radiotherapy; recurrence; tumor resistance; volumetric modulated arc therapy.

Figure 1

Site of first recurrence. Number of patients with a recurrence in the different sites. Overlapping circles show combination possibilities. There were one isolated local recurrence outside CTVp and one isolated regional recurrence outside CTVe. The numbers in the shaded area represent persistent tumors after the end of treatment, included in the total number of recurrences, e.g., 10 of 16 RR were persistent after treatment. CTVe, elective clinical target volume; DM, distant metastases; HNC, head and neck cancer; LR, local recurrence; RR, regional recurrence; SP, second primary.

Figure 2

Axial CT scan images of the only patient with a local recurrence outside of the high-dose volume. (A) The primary tumor originating in the vallecula and (B) CT scan of the local recurrence in the prelaryngeal space, approximately 1 cm caudal of the index tumor.