| Abstract | Usporediti našu standardnu tehniku za isporuku radioterapije kod karcinoma prostate niskog rizika, volumenski moduliranu lučnu terapiju RapidArc-RA® (Varian Medical Systems, Palo Alto, CA, USA) s dinamičkom konformalnom lučnom terapijom (DCAT). Planovi su referirani kao RA, odnosno DCAT subsekventno.
Materijali i metode: Analizirani su planovi liječenja 38 pacijenata liječenih RA radioterapijom između 2016. i 2019. godine. Za sve pacijente izrađen je dodatni DCAT plan u svrhu dozimetrijske analize. Propisana ukupna doza bila je 78 Gy (2 Gy po frakciji) za obje tehnike. I RA i DCAT planovi optimizirani su u smislu pokrivenosti ciljnog i ograničenja na organe rizika. U svrhu usporedbe prikupljeni su apsolutni volumeni, promjeri ekvivalentne sfere PTV-a, mokraćnog mjehura i rektuma, a poprečni presjeci prikupljeni su samo za rektum.
Rezultati: Uočene su male razlike između tehnika kod pokrivenosti ciljnog volumena (PTV-a), dok su zabilježene značajne razlike u poštedi organa rizika (OAR) (p <0,0001). Vrijednosti OAR (srednja vrijednost ± sd; raspon) bile su: mjehur: V65Gy = 16 ± 7,8% (5-42,7) i 25,1 ± 13,5% (8-73,5%), V70Gy = 13,5 ± 6,9% (4-35,7%) i 20,4 ± 12,7% (3,2-62,7%), V75Gy = 10,5 ± 5,9% (0-27,6%) i 13,6 ± 9,4 (0-43), V80Gy = 0,9 ± 0,8% (0-2,4%) i 0,3 ± 1% (0-4,5%); rektum: V60Gy = 16,8 ± 6,8% (6,8-36,4) i 36,9 ± 13,6% (11,1-62,5%), V65Gy = 13,4 ± 5,9% (4,9-29,2%) i 31,8 ± 11,7% (10-57,4%), V70Gy = 10,6 ± 4,9% (1,1-23,3%) i 25 ± 10,9 (3,8-51,9), V75Gy = 7 ± 3,5% (0-15,9%) i 017,7 ± 8,5% (0-40,7%), za RA i DCAT. Broj monitorskih jedinica (MU) je 610 ± 94 nasuprot 329 ± 17 za RA i DCAT.
Zaključak: Histogrami doze volumena (DVH) pokazuju bolju poštedu OAR-a s RA u odnosu na DCAT. Međutim, RA tehnika povezana je s gotovo dvostrukim brojem MU-a u usporedbi s DCAT-om. Što se tiče PTV-a, DCAT je malo superiorniji u pogledu V95% i indeksa konformalnosti. U cjelini, rezultati sugeriraju da je RA superiornija tehnika, međutim DCAT je također primjenjiv u nekim odabranim slučajevima. |
| Abstract (english) | Purpose: To compare our standard technique for radiotherapy of low risk prostate cancer, i.e. one volumetric-modulated arc using Rapid Arc (®) (Varian Medical Systems, Palo Alto, CA, USA), with DCAT (dynamic conformal arc technique). The plans were referred to as RA and DCAT, respectively.
Materials and methods: The treatment plans of 38 patients treated with RA radiotherapy between 2016 and 2019 were analyzed. For all patients additional DCAT plan was created for the purpose of dosimetric analysis. The prescribed total dose was 78 Gy (2 Gy per fraction) for both techniques. Both RA and DCAT plans were optimized in terms of dose coverage and constraints. For the purpose of comparison, absolute volumes, equivalent sphere diameters of PTV, bladder and rectum were collected, cross sectional area (CSA) was collected only for rectum.
Results: Small differences between the techniques were observed for planning target volume (PTV) dose coverage, whereas significant differences in sparing of organs at risk (OARs) were recorded (p < 0.0001). The OAR values (mean±sd; range) were: bladder: V65Gy=16±7.8% (5-42.7) and 25.1±13.5% (8-73.5%), V70Gy = 13.5±6.9% (4-35.7%) and 20.4±12.7% (3.2-62.7%), V75Gy= 10.5±5.9% (0-27.6%) and 13.6±9.4 (0-43), V80Gy=0.9±0.8% (0-2.4%) and 0.3±1% (0-4.5%); rectum: V60Gy=16.8±6.8% (6.8-36.4) and 36.9±13.6% (11.1-62.5%), V65Gy = 13.4±5.9% (4.9-29.2%) and 31.8±11.7% (10-57.4%), V70Gy=10.6±4.9% (1.1-23.3%) and 25±10.9 (3.8-51.9), V75Gy=7±3.5% (0-15.9%) and 017.7±8.5% (0-40.7%), for RA and DCAT, respectively. Monitor units (MU) were 610±94 versus 329±17 for RA and DCAT, respectively.
Conclusion: Dose-volume histograms (DVHs) showed improvements in OAR sparing with RA. However, the RA technique is associated with almost double number of MUs compared to DCAT. Regarding the PTV, DCAT is slightly superior in terms of V95% and conformity. On the whole, the results suggest that RA is the favorable technique, however DCAT is also applicable in some selected
cases. |
