Dosimetric comparison between proton beam therapy and photon radiation therapy for locally advanced non-small cell lung cancer

Abstract

Objective: To assess the feasibility of proton beam therapy for the patients with locally advanced non-small lung cancer. Methods: The dosimetry was analyzed retrospectively to calculate the doses to organs at risk, such as the lung, heart, esophagus and spinal cord. A dosimetric comparison between proton beam therapy and dummy photon radiotherapy (three-dimensional conformal radiotherapy) plans was performed. Dummy intensity-modulated radiotherapy plans were also generated for the patients for whom curative three-dimensional conformal radiotherapy plans could not be generated. Results: Overall, 33 patients with stage III non-small cell lung cancer were treated with proton beam therapy between December 2011 and August 2014. The median age of the eligible patients was 67 years (range: 44-87 years). All the patients were treated with chemotherapy consisting of cisplatin/vinorelbine or carboplatin. The median prescribed dose was 60 GyE (range: 60-66 GyE). The mean normal lung V20 GyE was 23.6% (range: 14.9-32%), and the mean normal lung dose was 11.9 GyE (range: 6.0-19 GyE). The mean esophageal V50 GyE was 25.5% (range: 0.01-63.6%), the mean heart V40 GyE was 13.4% (range: 1.4-29.3%) and the mean maximum spinal cord dose was 40.7 GyE (range: 22.9-48 GyE). Based on dummy three-dimensional conformal radiotherapy planning, 12 patients were regarded as not being suitable for radical thoracic three-dimensional conformal radiotherapy. All the dose parameters of proton beam therapy, except for the esophageal dose, were lower than those for the dummy three-dimensional conformal radiotherapy plans. In comparison to the intensity-modulated radiotherapy plan, proton beam therapy also achieved dose reduction in the normal lung. None of the patients experienced grade 4 or worse non-hematological toxicities. Conclusions: Proton beam therapy for patients with stage III non-small cell lung cancer was feasible and was superior to three-dimensional conformal radiotherapy for several dosimetric parameters.

The evolution of proton beam therapy: Current and future status (Review)

“…In comparison with photons, PBT plans may deliver lower doses to the adjacent organs at risk, such as the esophagus, lungs and bone marrow, thus improving the therapeutic ratio (15). The early clinical outcome of PBT in lung cancer patients (16)(17)(18)(19)(20)(21)(22)(23) demonstrated that proton beam therapy combined with chemotherapy may relatively reduce the rates of toxicity and achieve a possible survival benefit compared with photon beam therapy and 3DCRT (24). Early results (25)(26)(27)(28)(29) suggested that PBT has the advantage of dose escalation, which may prolong patient survival, lower the risk of recurrence and severe toxicity, and intensify chemotherapy (15).…”

Proton therapy: the current status of the clinical evidences

“…If the lateral beam placement is avoided to reduce the lung dose, the irradiated dose to heart is consequently increased and results in increased cardiac death in long-term follow-up. In many dosimetric studies, proton therapy demonstrated advantages in lung and heart dose compared with photon therapy [52][53][54]. Several clinical studies have reported treatment outcomes and toxicities of proton therapy in early-stage disease, locally advanced disease, re-irradiation, and in postoperative settings [55].…”

Adaptive Radiotherapy for Lung Cancer Using Uniform Scanning Proton Beams

“…For locally advanced Stage III NSCLC patients, Wu et al. found that proton beam therapy was feasible and superior to three-dimensional conformal radiotherapy for several dosimetric parameters such as the mean dose for lung, heart, and spinal cord [3]. Using IMPT, doses to normal tissues, such as the lung, spinal cord, heart, and esophagus, can be further reduced compared to passive scattering proton therapy and IMRT for extensive Stage IIIB NSCLC, as reported by Zhang et al [10].…”

“…Because of proton beams' finite range, proton beam therapy (PBT) has been increasingly used for lung cancer. Compared to 3D conformal or intensity modulated photon radiation (IMRT), proton beams can better spare the lung, esophagus, heart, cord, and other normal tissues while delivering the same or higher dose to the treatment target [2][3][4]. The dosimetric advantage of proton therapy could lead to potential better tumor control and less toxicity.…”