Fully automated VMAT treatment planning for advanced-stage NSCLC patients

PURPOSE

To develop a fully automated procedure for multicriterial volumetric modulated arc therapy (VMAT) treatment planning (autoVMAT) for stage III/IV non-small cell lung cancer (NSCLC) patients treated with curative intent.

MATERIALS AND METHODS

After configuring the developed autoVMAT system for NSCLC, autoVMAT plans were compared with manually generated clinically delivered intensity-modulated radiotherapy (IMRT) plans for 41 patients. AutoVMAT plans were also compared to manually generated VMAT plans in the absence of time pressure. For 16 patients with reduced planning target volume (PTV) dose prescription in the clinical IMRT plan (to avoid violation of organs at risk tolerances), the potential for dose escalation with autoVMAT was explored.

RESULTS

Two physicians evaluated 35/41 autoVMAT plans (85%) as clinically acceptable. Compared to the manually generated IMRT plans, autoVMAT plans showed statistically significant improved PTV coverage (V_95% increased by 1.1% ± 1.1%), higher dose conformity (R₅₀ reduced by 12.2% ± 12.7%), and reduced mean lung, heart, and esophagus doses (reductions of 0.9 Gy ± 1.0 Gy, 1.5 Gy ± 1.8 Gy, 3.6 Gy ± 2.8 Gy, respectively, all p < 0.001). To render the six remaining autoVMAT plans clinically acceptable, a dosimetrist needed less than 10 min hands-on time for fine-tuning. AutoVMAT plans were also considered equivalent or better than manually optimized VMAT plans. For 6/16 patients, autoVMAT allowed tumor dose escalation of 5-10 Gy.

CONCLUSION

Clinically deliverable, high-quality autoVMAT plans can be generated fully automatically for the vast majority of advanced-stage NSCLC patients. For a subset of patients, autoVMAT allowed for tumor dose escalation.

Single Vocal Cord Irradiation: Image Guided Intensity Modulated Hypofractionated Radiation Therapy for T1a Glottic Cancer: Early Clinical Results

PURPOSE

To report, from a retrospective analysis of prospectively collected data, on the feasibility, outcome, toxicity, and voice-handicap index (VHI) of patients with T1a glottic cancer treated by a novel intensity modulated radiation therapy technique developed at our institution to treat only the involved vocal cord: single vocal cord irradiation (SVCI).

METHODS AND MATERIALS

Thirty patients with T1a glottic cancer were treated by means of SVCI. Dose prescription was set to 16 × 3.63 Gy (total dose 58.08 Gy). The clinical target volume was the entire vocal cord. Setup verification was done by means of an online correction protocol using cone beam computed tomography. Data for voice quality assessment were collected prospectively at baseline, end of treatment, and 4, 6, and 12 weeks and 6, 12, and 18 months after treatment using VHI questionnaires.

RESULTS

After a median follow-up of 30 months (range, 7-50 months), the 2-year local control and overall survival rates were 100% and 90% because no single local recurrence was reported and 3 patients died because of comorbidity. All patients have completed the intended treatment schedule; no treatment interruptions and no grade 3 acute toxicity were reported. Grade 2 acute dermatitis or dysphagia was reported in only 5 patients (17%). No serious late toxicity was reported; only 1 patient developed temporary grade 2 laryngeal edema, and responded to a short-course of corticosteroid. The VHI improved significantly, from 33.5 at baseline to 9.5 and 10 at 6 weeks and 18 months, respectively (P<.001). The control group, treated to the whole larynx, had comparable local control rates (92.2% vs 100%, P=.24) but more acute toxicity (66% vs 17%, P<.0001) and higher VHI scores (23.8 and 16.7 at 6 weeks and 18 months, respectively, P<.0001).

CONCLUSION

Single vocal cord irradiation is feasible and resulted in maximal local control rate at 2 years. The deterioration in VHI scores was slight and temporary and subsequently improved to normal levels. Long-term follow-up is needed to consolidate these promising results.

Unilateral neck irradiation for well-lateralized oropharyngeal cancer

BACKGROUND AND PURPOSE

To investigate the impact of unilateral neck irradiation (UNI) of well-lateralized oropharyngeal cancer (OPC) on outcome and toxicity.

MATERIALS AND METHODS

Unilateral neck IMRT was applied to 185 consecutive patients with well-lateralized OPC (restricted to tonsillar fossa, soft palate with at least 1cm from midline or lateral pharyngeal wall). Endpoints were regional control (RC), local control (LC), disease-free survival (DFS), overall survival (OS), and toxicity.

RESULTS

Six regional failures were reported (3.2%); 2 were contralateral (1.1%). The 5-year Kaplan-Meier estimates of RC, LC, DFS, and OS were 96%, 91%, 84%, and 70%, respectively. Feeding tube was given to 11.3%. Chemotherapy was significantly predictive for toxicity. However, no patient was still feeding tube dependent 6 weeks after treatment. Overall grade 3 late toxicity was 2.2%. Grade 3 xerostomia was reported in only 1 patient while no patient developed grade 3 dysphagia.

CONCLUSION

This largest study on unilateral neck IMRT for well-lateralized OPC showed excellent outcome and favorable toxicity profile. Given the increasing incidence of OPC, especially among younger patients, and the favorable results reported in the current study and by other investigators, expanding the indications for UNI still needs to be further investigated in prospective, preferably, randomized trials.

Toward fully automated multicriterial plan generation: a prospective clinical study

PURPOSE

To prospectively compare plans generated with iCycle, an in-house-developed algorithm for fully automated multicriterial intensity modulated radiation therapy (IMRT) beam profile and beam orientation optimization, with plans manually generated by dosimetrists using the clinical treatment planning system.

METHODS AND MATERIALS

For 20 randomly selected head-and-neck cancer patients with various tumor locations (of whom 13 received sequential boost treatments), we offered the treating physician the choice between an automatically generated iCycle plan and a manually optimized plan using standard clinical procedures. Although iCycle used a fixed "wish list" with hard constraints and prioritized objectives, the dosimetrists manually selected the beam configuration and fine tuned the constraints and objectives for each IMRT plan. Dosimetrists were not informed in advance whether a competing iCycle plan was made. The 2 plans were simultaneously presented to the physician, who then selected the plan to be used for treatment. For the patient group, differences in planning target volume coverage and sparing of critical tissues were quantified.

RESULTS

In 32 of 33 plan comparisons, the physician selected the iCycle plan for treatment. This highly consistent preference for the automatically generated plans was mainly caused by the improved sparing for the large majority of critical structures. With iCycle, the normal tissue complication probabilities for the parotid and submandibular glands were reduced by 2.4% ± 4.9% (maximum, 18.5%, P=.001) and 6.5% ± 8.3% (maximum, 27%, P=.005), respectively. The reduction in the mean oral cavity dose was 2.8 ± 2.8 Gy (maximum, 8.1 Gy, P=.005). For the swallowing muscles, the esophagus and larynx, the mean dose reduction was 3.3 ± 1.1 Gy (maximum, 9.2 Gy, P<.001). For 15 of the 20 patients, target coverage was also improved.

CONCLUSIONS

In 97% of cases, automatically generated plans were selected for treatment because of the superior quality. Apart from the improved plan quality, automatic plan generation is economically attractive because of the reduced workload.