Radiation therapy in locally advanced pancreatic cancer with 75 Gy simultaneous integrated boost: a dosimetric feasibility study

doi:10.19401/j.cnki.1007-3639.2023.01.006

Abstract

Abstract:

Background and purpose: The incidence of pancreatic cancer has increased annually. Intensity-modulated radiotherapy (IMRT) has been widely used in the treatment of pancreatic cancer, however most dosimetric studies for pancreatic cancer have prescribed doses less than 60 Gy. The purpose of this study was to investigate the feasibility and dosimetric differences between coplanar IMRT (CO-IMRT) and non-coplanar IMRT (NC-IMRT) when using 75 Gy simultaneous integrated boost for patients with locally advanced pancreatic cancer (LAPC). Methods: Ten patients with LAPC treated with simultaneous integrated boost at Fudan University Shanghai Cancer Center from January 2018 to December 2021 were included. The prescribed dose for the planning target volume (PTV)_{50 Gy} was 50 Gy in 25 fractions, and 75 Gy in 25 fractions for the simultaneous integrated boost PTV_{75 Gy}. CO-IMRT and NC-IMRT plans were designed for each patient separately, with identical number of fields, prescription doses and OAR constrains for the same patient. The PTV dose distribution, conformability index (CI), homogeneity index (HI), indices to organs at risk (OAR) for multiple end points, beam-on time and monitor units (MU) were analyzed. We evaluated whether the PTV met clinical requirements and quantitative analysis of normal tissue effects in the clinic (QUANTEC) limits, and compared dosimetric differences between the two plans. Results: Both CO-IMRT and NC-IMRT could achieve the required dose coverage of PTV and meet the QUANTEC dose limits for OAR. The differences in CI, HI, beam-on time and MU between the two plans were not statistically significant (P>0.05). NC-IMRT was significantly decreased left kidney D_mean[(10.15±1.53) Gy vs (9.29±1.78) Gy, P<0.05], left kidney V₁₂[(32.74±7.45)% vs (26.03±8.97)%, P<0.05], right kidney D_mean[(7.37±2.41) Gy vs (6.62±2.37)Gy, P<0.05], right kidney V₁₂[(22.27±10.30)% vs (14.94±8.62)%, P<0.05], liver V₃₀[(6.37±4.05)% vs (5.47±3.70)%, P<0.05], small intestine V₃₀[(9.96±6.66)% vs (8.73±6.19)%, P<0.05], small intestine V₄₅[(1.15±0.71)% vs (0.96±0.61)%, P<0.05], stomach V₄₅[(5.37±3.96)% vs (4.52±3.32)%, P<0.05] and large bowel V₃₀[(13.18±4.95)% vs (9.19±4.94)%, P<0.05]. There was no significant difference between CO-IMRT and NC-IMRT in spinal cord D_max, liver D_mean, bilateral renal V₂₀, bilateral renal V₂₈, small intestinal D_max, gastric D_max and duodenal V_55(mL) (P >0.05). Conclusion: In the treatment of LAPC using 75 Gy simultaneous integrated boost, both CO-IMRT and NC-IMRT can achieve excellent PTV coverage and meet the OAR constraints in all patients. Without affecting the quality of PTV coverage, NC-IMRT has more advantages in the dose distribution of OAR, which can better protect the OAR and reduce the toxicity to the gastrointestinal tract, liver and kidneys.

Key words: Locally advanced pancreatic cancer, Intensity-modulated radiotherapy, Dosimetry

CLC Number:

R735.9

ZHUANG Han, LING Chifang, WANG Jiazhou, HAN Xu, JIANG Rui, HU Weigang. Radiation therapy in locally advanced pancreatic cancer with 75 Gy simultaneous integrated boost: a dosimetric feasibility study[J]. China Oncology, 2023, 33(1): 54-60.

Figures/Tables 7

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Structure	Requirement
PTV_{50 Gy}	The dose of 50 Gy includes at least 95% PTV_{50 Gy}
PTV_{75 Gy}	The dose of 75 Gy includes at least 95% PTV_{75 Gy}
Spinal cord	D_max<45 Gy
Liver	D_mean<18 Gy; V₃₀<50%
Kidney	D_mean<15 Gy; V₁₂<55%; V₂₀<32%; V₂₈<20%
Small intestine	D_max<54 Gy; V₃₀<25%; V₄₅<15%
Stomach	D_max<60 Gy; V₄₅<15%
Duodenum	V_55(mL)<1 cm³
Large bowel	V₃₀<50%

Item	CO-IMRT	NC-IMRT	P value
PTV_{50 Gy} CI	0.824±0.031	0.832±0.033	0.406
PTV_{75 Gy} CI	0.914±0.016	0.915±0.012	0.672
PTV_{75 Gy} HI	0.039±0.008	0.038±0.007	0.722

Structure	CO-IMRT	NC-IMRT	P value	Structure	CO-IMRT	NC-IMRT	P value
Spinal cord				V₂₀ /%	4.52±4.34	3.50±4.37	0.093
D_max /Gy	34.88±2.87	34.76±4.75	0.959	V₂₈ /%	1.05±1.53	1.42±2.28	0.463
Liver				Small intestine
D_mean /Gy	9.66±3.04	9.64±2.84	0.878	D_max /Gy	52.66±4.78	52.00±5.88	0.333
V₃₀ /%	6.37±4.05	5.47±3.70	0.013	V₃₀ /%	9.96±6.66	8.73±6.19	0.028
Left kidney				V₄₅ /%	1.15±0.71	0.96±0.61	0.024
D_mean /Gy	10.15±1.53	9.29±1.78	0.005	Stomach
V₁₂ /%	32.74±7.45	26.03±8.97	0.005	D_max /Gy	57.28±2.90	56.84.55±3.22	0.074
V₂₀ /%	11.14±6.65	10.19±5.12	0.575	V₄₅ /%	5.37±3.96	4.52±3.32	0.009
V₂₈ /%	4.18±3.15	4.91±3.21	0.059	Duodenum
Right kidney				V₅₅/mL	0.02±0.06	0.02±0.06	0.317
D_mean /Gy	7.37±2.41	6.62±2.37	0.005	Large bowel
V₁₂ /%	22.27±10.30	14.94±8.62	0.005	V₃₀ /%	13.18±4.95	9.19±4.94	0.005

Item	CO-IMRT	NC-IMRT	P value
Beam on time/min	2.55±0.45	2.56±0.38	0.799
MU	1529±270	1531±219	0.721