D7-01: 4-dimensional respiration-gated radiotherapy for concurrent chemo-radiotherapy in lung cancer

Abstract

4-dimensional respiration-gated radiotherapy for concurrent chemo-radiotherapy in lung cancer Senan, Suresh1 Spoelstra, Femke O.1 Phernambucq, Erik C.2 van Sornsen de Koste, John R.1 Cuijpers, Johan C.1 Smit, Egbert F.2 Slotman, Ben J.1 Lagerwaard, Frank J.1 1 Department of Radiation Oncology, VU University Medical Center, Amsterdam, The Netherlands 2 Department of Pulmonology, VU University Medical Center, Amsterdam, The Netherlands Background: Concurrent chemo-radiotherapy (CT-RT) is the treatment of choice in locally advanced lung cancer, but it is associated with increased esophageal and lung toxicity. Toxicity can be reduced using respiration-gated radiotherapy (RGRT) in which treatment is delivered during pre-selected phases of the respiratory cycle, thereby allowing for smaller target volumes. The feasibility of such interventions for motion management during thoracic CT-RT is unknown. We studied the compliance and toxicity of RGRT in this setting. Methods: Details of gated concurrent CT-RT were analyzed in 31 consecutive patients with a minimum follow-up of 3 months. They included 28 with locally-advanced non-small cell lung cancer (LANSCLC) and 3 with limited-stage SCLC. A subgroup of LA-NSCLC patients underwent induction CT-RT, followed by mediastinal re-staging and surgery in downstaged patients. Concurrent chemotherapy consisted of either 2-3 cycles of cisplatin-etoposide or weekly cycles of cisplatin-docetaxel. Involved-field radiotherapy was delivered to a target volume defined using a 4-dimensional (4D) CT scan, FDG-PET and biopsy-proven nodal disease. The Varian Real-time Position Management respiratory gating system (Varian Medical Systems) was used for 4DCT acquisition, and for treatment delivery. A dose of 45-60 Gy was delivered in once-daily fractions of 1.8-2.0 Gy on a Varian 2100 C/D linear accelerator. RGRT was performed using either (i) audio-coached, phase-based gating in which radiation delivery is limited to the endinspiratory phase or (ii) amplitude-based gating in which radiation is delivered within the breathing threshold levels observed during 4DCT imaging. Audio-coached, end-inspiratory gating was the procedure of choice when tumour motion exceeded 7.5 mm and/or when a significant increase in total lung volume was expected. All other patients were treated with amplitude-based gating. Results: Only 1 patient, who died of pulmonary haemorrhage during treatment, failed to complete the planned treatment. Ten patients who were downstaged underwent surgical resection. The median follow-up was 5 months. The median planning target volume (PTV) was 649.9 cc (range 274-1616). The percentage of lung volume receiving a threshold dose of 20 Gy (V20) ranged from 12.4 44.6%. The median oesophageal circumference receiving 46 Gy was 6.6 (range 0-13.5) cm. CTC grade 3 esophagitis was observed in 23% (7 pts), and 52% (16 pts.) developed grade 2 esophagitis. The mean weight loss was 2.9 kg (range 0.5-10) and 13 patients treated with preoperative CT-RT received a feeding tube, which was a prophylactic measure in 6 patients. CTC grades 2 and 3 radiation pneumonitis developed in 2 patients at 4 and 3 months, respectively, post-treatment. At the last follow-up, 23 patients were free from disease progression. Five patients had extrathoracic metastases, with 4 having exclusively distant metastasis. Loco-regional failure was observed in 3 patients, with two being out-of-field recurrences. Conclusion: RGRT is well tolerated in patients undergoing concurrent CT-RT for lung cancer. The treatment drop-out rate of 3% in this unselected cohort compares favourably with the rates of 16-19% reported in phase III trials in LA-NSCLC [Fournel 2005; Albain 2005]. Updated results at a median follow-up of 11 months will be available.