Partial stereotactic ablative boost radiotherapy in bulky non-small cell lung cancer: a dosimetric comparison between proton and photon / 中华放射肿瘤学杂志

Objective:Partial stereotactic ablative boost radiotherapy(P-SABR)is a method to deliver SABR boost to the gross tumor boost volume(GTVb), followed by conventionally fractionated radiotherapy to the whole tumor area(GTV). GTVb is the max volume receiving SABR while ensuring the critical organ-at-risk(OAR)falloff to 3 GyE/f. We investigated the potential advantage of proton therapy in treating bulky non-small cell lung cancer(the tumor length greater than 8 cm).Methods:Nine patients with bulky NSCLC treated with photon P-SABR in our institute were selected. For the treatment planning of proton therapy, the GTVb target area was gradually outwardly expanded based on the photon GTVb target area until the dose to critical OARs reached 3 GyE/f. The GTV and CTV areas remained the same as photon plan. A proton intensity-modulated radiation treatment plan(proton-IMPT), a photon intensity-modulated radiation treatment plan(photon-IMRT)and a photon volumetric modulated arc therapy(photon-VMAT)were created for each patient, respectively. The dosimetric parameters of different treatment plans were compared.Results:The volume ratio of GTVb-photon and GTVb-proton to GTV was(25.4±13.4)% and(69.7±30.0)%,respectively( P<0.001). In photon-IMRT, photon-VMAT, and proton-IMPT plan groups, the mean dose of CTV was(76.1±4.9)Gy, (78.2±3.6)Gy, and(84.7±4.9)Gy, respectively; the ratio of tumor volume with Biologic Effective Dose(BED)≥ 90 Gy to GTV volume was(70.7±21.7)%, (76.8±22.1)%,and(97.9±4.0)%,respectively. The actual dose and BED to the tumor area of the proton-IMPT plan group were significantly higher than those of the photon plan group(both P<0.05). Besides, the OARs dose was significantly decreased in the proton-IMPT group, with(49.2±22.0)%, (56.8±19.0)% and(16.1±6.3)% of the whole lung V5 for photon-IMRT, photon-VMAT and proton-IMPT, respectively(all P<0.001). Conclusions:Larger GTV boost target volume, higher BED and reduced OARs dose can be achieved in proton plans compared with photon plans. Proton P-SABR is expected to further improve the local control rate of bulky NSCLC with fewer adverse effects.

Utilization of a scintillator detection system for quality assurance in carbon-ion and proton therapy / 中华放射肿瘤学杂志

Objective:A two-dimensional (2D) in-house-built scintillator detection system (SDS) was utilized for quality assurance of the active spot scanning proton and heavy ion accelerator, aiming to establish a rapid detection method and provide reference for the quality of proton and heavy ion beam (spot position, spot size, virtual source-to-axis distance, profile depth dose distribution and beam range).Methods:The SDS consisted of a ceramic gadolinium-sulfoxylate phosphor-scintillating screen, a mirror and a commercial digital camera. The dose distribution image was obtained based on scintillator, mirror reflector and optical signal acquisition device to transform the proton and heavy ion beam into visible light through sulfur gadolinium oxide scintillator and collect visible light information to meet the clinical requirements for the quality of proton and heavy ion beam.Results:The deviation of spot position measured by multifilament proportional chamber and the SDS was less than 1mm. The differences of beam spot size measured by multifilament proportional chamber and the SDS were (1.40±0.59)mm for protons, and (0.5±0.08)mm for carbon ions. For 429.25MeV/u carbon, the virtual source-to-axis distance (V SAD) at the x-and y-axes was 751.8cm and 805.6cm. And difference between physical distance and virtual source-to-axis distance was less than 1%. The range of 287.5MeV/u carbon measured by SDS was 160mm. Conclusions:The in-house-built scintillator detector can measure beam spot position and size, virtual source, depth distribution curve and range, which can be used as an effective tool for quality assurance control of proton and heavy ion therapy.

Preliminary study of pencil beam scanning proton and carbon ion therapy for chordoma and chondrosarcoma of head and neck / 中华放射肿瘤学杂志

Objective To evaluate the short-term efficacy and adverse events of pencil beam scanning proton and carbon ion therapy in the treatment of chordoma and chondrosarcoma of the head and neck.Methods Between July 2014 and July 31,2017,61 patients with chordoma and chondrosarcoma of the head and neck receiving proton and heavy ion therapy as the first course of radiotherapy were enrolled.Among them,45 patients were diagnosed with chordoma and 16 cases of chondrosarcoma,39 male and 22 female.The median age was 38 years old (range:14-70 years).The median maximum tumor diameter was 4.1 cm (range:0-8.6 cm).The clivus and the cervical spine were the primary tumor sites.Results Eight patients received proton therapy,21 patients were treated with proton combined with carbon ion therapy and 32 patients received carbon ion therapy.All patients successfully completed the planned radiotherapy.The medial follow-up time was 21 months (range:7-47 months).No grade 3-4 acute toxicity was observed.Only one patient suffered from radiation-induced temporal lobe injury.The 2-year progression-free survival (PFS)and overall survival (OS) were 91％ and 100％.Conclusions Pencil beam scanning proton and heavy ion therapy yields relatively favorable short-term outcomes in the treatment of chordoma and chondrosarcoma of the head and neck.Nevertheless,the long-term clinical efficacy and safety remain to be investigated during follow-up.

Practice of proton and heavy ion radiotherapies for head and neck malignancies / 中华放射肿瘤学杂志

Radiotherapy is an important therapeutic method in the management of head and neck cancer.However,since the head and neck region has many important functions of the human body,radiotherapy may cause serious sequelae.Proton and heavy ion radiotherapies have better radiophysical and biological properties compared with conventional proton beam and are beneficial to tumor control and protection of normal tissue.The advantages of proton and heavy ion radiotherapies have been demonstrated in soft tissue tumors (especially skull base chordoma and chondrosarcoma),malignant melanoma,and adenoid cystic carcinoma resistant to conventional protons in the head and neck region,and the safety of proton and heavy ion radiotherapies have been confirmed in reirradiation for recurrent tumors.

Dosimetric comparison between proton therapy and X-ray intensity-modulated radiotherapy for cervical esophageal cancer / 中华放射肿瘤学杂志

Objective To compare the dosimetric difference of proton therapy(PT)and X-ray intensity-modulated radiotherapy(IMRT)for cervical esophageal cancer.Methods The treatment planning of 10 patients with cervical esophageal cancer were selected for this study.One IMRT plan and 2 PT plans (PT1 plan:two opposed AP-PA beams;PT2 plan:two anterior-oblique beams and one posterior beam)were constructed for each patient.The isodose distribution and statistical data extracted from dose volume histograms were used for dose plan comparison.Results The conformal index(CI95%,defined as the ratio between the volume receiving at least 95%of the prescribed dose and the volume of PTV)of IMRT,PT1 and PT2 was 1.43,1.52 and 1.43(F=3.62,P<0.01),respectively.And the mean dose of PTV was 64.4 Gy,65.0 Gy and 63.6 Gy(F=12.06,P<0.01);the mean dose in normal tissue outside of PTV was 20.7 Gy,10.5 Gy and 10.6 Gy(F=77.60,P<0.01),in whole lung was 12.1 Gy,7.3 Gy and 8.4 Gy (F=15.87,P<0.01);the maximum dose in spinal cord was 41.4 Gy,34.9 Gy and 35.0 Gy(F=11.74,P<0.01),respectively.Conclusions Ail plans full file the requirements for PTV,however.PT plans can reduce radiation dose in surrounding normal significantly.The possibility is provided to escalate PT dose in PTV or to combine more aggressive chemotherapy.The PT1 plan full fills the clinical requirements.