Clinical introduction of Monte Carlo treatment planning: a different prescription dose for non-small cell lung cancer according to tumor location and size.
OBJECTIVE
To provide a prescription dose for Monte Carlo (MC) treatment planning in patients with non-small-cell lung cancer according to tumor size and location.


METHODS
Fifty-three stereotactic radiotherapy plans designed using the equivalent path-length (EPL) algorithm were re-calculated using MC. Plans were compared by the minimum dose to 95% of the PTV (D95), the heterogeneity index (HI) and the mean dose to organs at risk (OARs). Based on changes in D95, the prescription dose was converted from EPL to MC. Based on changes in HI, we examined the feasibility of MC prescription to plans re-calculated but not re-optimized with MC.


RESULTS
The MC fraction dose for peripheral tumors is 16-18 Gy depending on tumor size. For central tumors the MC dose was reduced less than for peripheral tumors. The HI decreased on average by 4-9% in peripheral tumors and 3-5% in central tumors. The mean dose to OARs was lower for MC than EPL, and correlated strongly (R(2)=0.98-0.99).


CONCLUSIONS
For the conversion from EPL to MC we recommend a separate prescription dose according to tumor size. MC optimization is not required if a HI > or = 70% is accepted. Dose constraints to OARs can be easily converted due to the high EPL-MC correlation.
van der Voort van Zyp
Noëlle C
NC
Department of Radiation Oncology, Erasmus MC-Daniel den Hoed Cancer Center, Rotterdam, The Netherlands. n.vandervoortvanzyp@erasmusmc.nl
Hoogeman
Mischa S
MS
van de Water
Steven
S
Levendag
Peter C
PC
van der Holt
Bronno
B
Heijmen
Ben J M
BJ
Nuyttens
Joost J
JJ
D002289:Carcinoma, Non-Small-Cell Lung / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery*; D004307:Dose-Response Relationship, Radiation; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery*; D008297:Male; D009010:Monte Carlo Method; D009361:Neoplasm Invasiveness / Q000473:pathology; D009367:Neoplasm Staging; D011859:Radiography; D016634:Radiosurgery / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*