Proton Therapy in the Management of Pancreatic Cancer

Adaptive intensity modulated proton therapy using 4D robust planning: a proof-of-concept for the application of dose mimicking approach

Objective.A four-dimensional robust optimisation (4DRO) is usually employed when the tumour respiratory motion needs to be addressed. However, it is computationally demanding, and an automated method is preferable for adaptive planning to avoid manual trial-and-error. This study proposes a 4DRO technique based on dose mimicking for automated adaptive planning.Approach.Initial plans for 4DRO intensity modulated proton therapy were created on an average CT for four patients with clinical target volume (CTV) in the lung, oesophagus, or pancreas, respectively. These plans were robustly optimised using three phases of four-dimensional computed tomography (4DCT) and accounting for setup and density uncertainties. Weekly 4DCTs were used for adaptive replanning, using a constant relative biological effectiveness (cRBE) of 1.1. Two methods were used: (1) template-based adaptive (TA) planning and (2) dose-mimicking-based adaptive (MA) planning. The plans were evaluated using variable RBE (vRBE) weighted doses and biologically consistent dose accumulation (BCDA).Main results.MA and TA plans had comparable CTV coverage except for one patient where the MA plan had a higher D98 and lower D2 but with an increased D2 in few organs at risk (OARs). CTV D98 deviations in non-adaptive plans from the initial plans were up to -7.2 percentage points (p.p.) in individual cases and -1.8 p.p. when using BCDA. For the OARs, MA plans showed a reduced mean dose and D2 compared to the TA plans, with few exceptions. The vRBE-weighted accumulated doses had a mean dose and D2 difference of up to 0.3 Gy and 0.5 Gy, respectively, in the OARs with respect to cRBE-weighted doses.Significance.MA plans indicate better performance in target coverage and OAR dose sparing compared to the TA plans in 4DRO adaptive planning. Moreover, MA method is capable of handling both forms of anatomical variation, namely, changes in density and relative shifts in the position of OARs.

Comparing different boost concepts and beam configurations for proton therapy of pancreatic cancer

Background and Purpose

Interfractional geometrical and anatomical variations impact the accuracy of proton therapy for pancreatic cancer. This study investigated field-in-field (FIF) and simultaneous integrated boost (SIB) concepts for scanned proton therapy treatment with different beam configurations.

Materials and Methods

Robustly optimized treatment plans for fifteen patients were generated using FIF and SIB techniques with two, three, and four beams. The prescribed dose in 20 fractions was 60 Gy(RBE) for the internal gross tumor volume (IGTV) and 46 Gy(RBE) for the internal clinical target volume. Verification computed tomography (vCT) scans was performed on treatment days 1, 7, and 16. Initial treatment plans were recalculated on the rigidly registered vCTs. V100% and D95% for targets and D2cm3 for the stomach and duodenum were evaluated. Robustness evaluations (range uncertainty of 3.5 %) were performed to evaluate the stomach and duodenum dose-volume parameters.

Results

For all techniques, IGTV V100% and D95% decreased significantly when recalculating the dose on vCTs (p < 0.001). The median IGTV V100% and D95% over all vCTs ranged from 74.2 % to 90.2 % and 58.8 Gy(RBE) to 59.4 Gy(RBE), respectively. The FIF with two and three beams, and SIB with two beams maintained the highest IGTV V100% and D95%. In robustness evaluations, the ΔD2cm3 of stomach was highest in two beams plans, while the ΔD2cm3 of duodenum was highest in four beams plans, for both concepts.

Conclusion

Target coverage decreased when recalculating on CTs at different time for both concepts. The FIF with three beams maintained the highest IGTV coverage while sparing normal organs the most.

Impact and optimal timing of local therapy addition in borderline resectable or locally advanced pancreatic cancer after FOLFIRINOX chemotherapy

Background

To evaluate the efficacy and optimal timing of local treatment in patients with borderline resectable (BR) or locally advanced pancreatic cancer (LAPC) treated with upfront FOLFIRINOX.

Method

Between 2015 and 2020, 258 patients with pancreatic ductal adenocarcinoma (PDAC) were analysed. Treatment outcomes were compared between systemic treatment group (ST) and multimodality treatment groups (MT) using Kaplan-Meier curves and log-rank test. The MT were stratified as follows: FOLFIRINOX + radiation therapy (RT) (MT1), FOLFIRINOX + surgical resection (MT2), and FOLFIRINOX + RT + surgical resection (MT3).

Results

With median follow-up period of 18 months, the 2-year overall survival (OS) for the ST was 22.0%, and it was significantly worse than MT (MT1, 46.3%; MT2, 65.7% and MT3; 90.2%; P < .001). The 2-year locoregional progression free survival (LRPFS) and overall PFS in ST were 10.7% and 7.0%, which were also significantly lower than those of MT (2-year LRPFS: MT1, 31.8%; MT2, 45.3%; MT3, 81.0%; 2-year overall PFS: MT1, 23.3%; MT2, 35.0%; MT3, 66.3%; P < .001). In time-varying multivariate Cox proportional hazard model, local treatment contributed to better treatment outcomes, with adjusted hazard ratios of 0.568 (95% confidence interval [CI], 0.398-0.811), 0.490 (95% CI, 0.331-0.726), and 0.656 (95% CI, 0.458-0.940) for OS, LRPFS, and overall PFS, respectively. The time window of 11-17 months after FOLFIRINOX appeared to demonstrate the maximal efficacy of local treatments in OS.

Conclusions

Adding local treatment in BR/LAPC patients treated with upfront FOLFIRINOX seemed to contribute in improved treatment outcomes, and it showed maximal efficacy in OS when applied 11-17 months after the initiation of FOLFIRINOX. We suggest that administration of sufficient period of upfront FOLFIRINOX may intensify the efficacy of local treatments, and well controlled prospective trials are expected.

Carbon-ion radiotherapy (CIRT) as treatment of pancreatic cancer at HIT: initial radiation plan analysis of the prospective phase II PACK-study

PURPOSE

To analyze the dose objectives and constraints applied at the prospective phase II PACK-study at Heidelberg ion therapy center (HIT) for different radiobiological models.

METHODS

Treatment plans of 14 patients from the PACK-study were analyzed and recomputed in terms of physical, biological dose and dose-averaged linear energy transfer (LETd). Both LEM-I (local effect model 1) and the adapted NIRS-MKM (microdosimetric kinetic model), were used for relative biological effectiveness (RBE)-weighted dose calculations (DBio|HIT and DBio|NIRS). A new constraint to the gastrointestinal (GI) tract was derived from the National Institute of Radiological Science (NIRS) clinical experience and considered for plan reoptimization (DBio|NIRS-const_48Gy and DBio|NIRS-const_50.4Gy). The Lyman-Kutcher-Burman (LKB) model of Normal Tissue Complication Probability (NTCP) for GI toxicity endpoints was computed. Furthermore, the computed LETd distribution was evaluated and correlated with Local Control (LC).

RESULTS

Only two patients showed a LETd98% in the GTV greater than 44 keV/μm. A HIT-dose constraint to the GI of [Formula: see text] was derived from the NIRS experience, in alternative to the standard at HIT Dmax = 45.6 GyRBEHIT. In comparison with the original DBio|HIT,DBio|NIRS-const_48GyandDBio|NIRS-const_50.4Gy resulted in an increase in the ITV's D98% of 8.7% and 11.3%. The NTCP calculation resulted in a probability for gastrointestinal bleeding of 4.5%, 12.3% and 13.0%, for DBio|NIRS, DBio|NIRS-const_48Gy and DBio|NIRS-const_50.4Gy, respectively.

CONCLUSION

The results indicate that the current standards applied at HIT for CIRT closely align with the Japanese experience. However, to enhance tumor coverage, a more relaxed constraint on the GI tract may be considered. As the PACK-trial progresses, further analyses of various clinical endpoints are anticipated.

The Feasibility of Stereotactic Body Proton Beam Therapy for Pancreatic Cancer

Background/Purpose: This study aimed to evaluate the clinical outcomes of stereotactic body proton beam therapy (SBPT) for pancreatic cancer. Methods: This retrospective study included 49 patients who underwent SBPT for pancreatic cancer between 2017 and 2020. Survival outcomes, bowel-related toxicities, and failure patterns were analysed. SBPT was performed after induction chemotherapy in 44 (89.8%) patients. The dose-fractionation scheme included 60 gray (Gy) relative biological effectiveness (RBE) in five fractions (n = 42, 85.7%) and 50 GyRBE in five fractions (n = 7, 14.3%). The median follow-up was 16.3 months (range, 1.8−45.0 months). Results: During follow-up, the best responses were complete response, partial response, and stable disease in four (8.2%), 13 (26.5%), and 31 (63.3%) patients, respectively. The 2-year overall survival, progression-free survival, and local control (LC) rates were 67.6%, 38.0%, and 73.0%, respectively. Grade ≥ 3 gastroduodenal (GD) toxicity occurred in three (6.1%) patients. Among them, one patient underwent endoscopic haemostasis. The other two patients received surgical management. They were followed up without disease progression for >30 months after SBPT. Overall, there was no significant dosimetric difference between the grade ≥ 2 and lower toxicity groups. Conclusions: SBPT provides relatively high LC rates with acceptable toxicities in pancreatic cancer.