- Email: [email protected]
Dose-volume Analysis of Predictors for Gastrointestinal Toxicity after Radiotherapy and Concurrent Full-dose Gemcitabine for Locally Advanced Pancreatic Adenocarcinoma
Proceedings of the 53rd Annual ASTRO Meeting toxicity was observed. Median follow-up was 10.4 months (9.5 – 18.0 months), while 4/11 patients died. The CR, PR SD and PD were 22.2% (2/9), 55.6% (5/9), 11.1% (1/9), and 11.1% (1/9) in 9 patients. While the CR, PR SD, and PD were 20.8% (2/ 10), 50.0% (5/10), 20.0% (2/10), and 10.0% (1/10) in 10 patients who received 6 weeks Nimotuzumab, respectively. Five of 10 patients relapsed or died (4 distant metastasis, 1 esophagus hemorrhea). Six-months and 1-year survival rates were 80% and 70%. Six-months and 1-year progression-free survival (PFS) rates were 80% and 60%, respectively. One-year local progression-free survival was 100%. Conclusions: Nimotuzumab administered 400 mg weekly with concurrent chemoradiotherapy based on PF regimen was welltolerant. No SAE related to Nimotuzumab was observed. MTD has not reached yet across the test doses in this study. This initial study represents a higher local control rate and survival in the treatment of locally advanced esophageal cancer. Author Disclosure: K. Zhao: None. G. Jiang: None. X. Hu: None. X. Wu: None. X. Fu: None. M. Fan: None.
1027
Long-term Outcomes of Neoadjuvant Chemotherapy (NC) before Chemoradiation (CRT) for Locally Advanced Pancreatic Cancer (LAPC)
N. D. Arvold1, D. P. Ryan2, A. Niemierko2, L. S. Blaszkowsky2, E. L. Kwak2, J. Y. Wo2, J. N. Allen2, R. C. Wadlow2, C. Fernandez-del Castillo2, T. S. Hong2 1
Harvard Radiation Oncology Program, Boston, MA, 2Massachusetts General Hospital, Boston, MA
Purpose/Objective(s): NC for patients with LAPC has been suggested as a means of selecting patients who will most benefit from CRT, but optimal management remains controversial and prior reports have had limited follow-up. Materials/Methods: We examined 70 consecutive patients with unresectable (n = 46) or borderline resectable (n = 24) LAPC treated with CRT at the Massachusetts General Hospital between July 2005 and November 2009. Patients typically received a radiation dose of 50.4 Gy in 1.8 Gy daily fractions (91%) with concurrent infusional 5-fluorouracil (84%) or capecitabine (14%). Forty patients (57%) received CRT alone, and 30 patients (43%) received NC before CRT (C-CRT) for a median of 4 months. NC was gemcitabine-based in 93% of patients, and all patients without progression after chemotherapy were offered CRT. Kaplan-Meier actuarial progression-free survival (PFS) and overall survival (OS) were estimated, groups were compared with log-rank tests, and Cox proportional hazard multivariate analysis (MVA) was used to analyze factors associated with PFS and OS. Results: Median age at diagnosis was 63 years and ECOG performance status score was 0 – 1 among 97% of patients. Median tumor size was 29 mm and 35 mm, and median CA 19 and 9 at presentation was 314 and 98, for the CRT and C-CRT groups, respectively. Fifty-three percent of patients in the CRT group were considered to have categorically unresectable tumors at diagnosis vs. 83% in the C-CRT group. After completion of CRT, 20% of patients were able to undergo surgical resection in the CRT group vs. 20% in the C-CRT group. Twenty-three percent of patients in the CRT group received intra-operative RT vs. 27% in the C-CRT group, to a median dose of 20 Gy (CRT) or 17 Gy (C-CRT), and adjuvant gemcitabine-based chemotherapy was received by 53% of patients in the CRT group vs. 37% in the C-CRT group. Median follow-up since diagnosis was 14.2 months. Median OS and PFS were 12.4 months and 6.7 months, respectively, in the CRT group and 18.7 months and 11.4 months in the C-CRT group (both p = 0.02). On MVA, receipt of NC (adjusted hazard ratio [AHR] = 0.49; 95% CI, 0.28 to 0.87; p = 0.02) and surgical resection (AHR = 0.38; 95% CI, 0.17 to 0.85; p = 0.02) were associated with increased OS. On MVA, receipt of NC (AHR = 0.41; 95% CI, 0.24 to 0.70; p = 0.001) and surgical resection (AHR = 0.26; 95% CI, 0.12 to 0.56; p = 0.001) were associated with increased PFS, and CA 19 and 9 level (continuous) after CRT (AHR = 1.14; 95% CI, 1.00 to 1.29; p = 0.045) was associated with decreased PFS. Conclusions: Our findings indicate a significant overall survival advantage with the use of gemcitabine-based NC to allow the selection of patients who will derive greatest benefit from CRT. The median survival we observed with this approach is similar to median survival reported in surgical series. Author Disclosure: N.D. Arvold: None. D.P. Ryan: None. A. Niemierko: None. L.S. Blaszkowsky: None. E.L. Kwak: None. J.Y. Wo: None. J.N. Allen: None. R.C. Wadlow: None. C. Fernandez-del Castillo: None. T.S. Hong: None.
1028
Dose-volume Analysis of Predictors for Gastrointestinal Toxicity after Radiotherapy and Concurrent Fulldose Gemcitabine for Locally Advanced Pancreatic Adenocarcinoma
J. Huang, J. M. Roberson, H. Ye, D. Yan William Beaumont Hospital, Royal Oak, MI Purpose/Objective(s): To identify dosimetric predictors for the development of gastrointestinal (GI) toxicity of patients with locally advanced pancreatic adenocarcinoma (LAPC) treated with concurrent full-dose gemcitabine and radiotherapy (GemRT). Materials/Methods: From June 2002 to June 2009, 46 LAPC patients treated with definitive GemRT at William Beaumont Hospital were retrospectively analyzed. Gemcitabine was administered at 1000 mg/m2 weekly during radiotherapy (RT). Twentyeight (61%) had concurrent gemcitabine alone (G-RT); eighteen (39%) had concurrent gemcitabine with daily erlotinib of 100 mg (GE-RT). RT was involved-field to treat the gross tumor volume with 1 cm margin. Thirty patients (65%) were treated on Phase I dose-escalation protocols. Median RT dose was 36 Gy (range, 22 – 42), and median fractional dose was 2.4 Gy (range, 2 – 2.8 Gy). RT technique was either 3D-conformal RT (3D-CRT, 87%) or intensity modulated RT (IMRT, 13%). Stomach and duodenum were retrospectively contoured to determine the dose-volume histogram (DVH) parameters. Duodenum was contoured from the duodenal bulb to the ligament of Treitz. GI toxicity was defined as $ Grade 3 GI toxicity using the National Cancer Institute Common Toxicity Criteria 4.0. The follow-up time was calculated from the start time of RT to the date of death or last contact. Univariate (UVA) and multivariate analyses (MVA) using Kaplan-Meier and Cox regression models were performed to identify risk factors associated with GI toxicity. Stepwise discriminant analysis (SDA) was used to determine the best DVH parameter to predict for GI toxicity.
S169
I. J. Radiation Oncology d Biology d Physics
S170
Volume 81, Number 2, Supplement, 2011
Results: After a median follow-up of 10.4 months (20.9 months for surviving patients), there were a total of 20 Grade-3 GI events among 17 patients. Actuarial Grade 3 GI toxicity rates were 26% at 3 months, 29% at 6 months, and 37% at 12 months. On UVA, only V20-35Gy of duodenum were significantly associated with GI toxicity (all p # 0.05). On MVA, V25Gy of duodenum and the use of erlotinib were independent risk factors for GI toxicity (p = 0.006 and 0.02, respectively). For the entire cohort, V25Gy of duodenum is the best predictor for GI toxicity (sensitivity = 52%, specificity = 71%, and accuracy = 59%), and the 12-month GI toxicity rate was 19% if V25Gy # 70% vs. 57% if V25Gy . 70% (p = 0.03). However, for the G-RT subset, V35Gy is the best predictor (sensitivity = 68%, specificity = 56%, and accuracy = 64%), and the 12-month GI toxicity rate was 10% if V35Gy # 25% vs. 42% if V35Gy . 25% (p = 0.06). Conclusions: DVH parameters of duodenum may be used to predict the development of Grade 3 GI toxicity after GemRT for LAPC. Concurrent use of erlotinib during GemRT may increase the risk of GI toxicity. Author Disclosure: J. Huang: None. J.M. Roberson: None. H. Ye: None. D. Yan: None.
1029
Stereotactic Body Radiation Therapy (SBRT) for Hepatocellular Carcinoma (HCC): Rationale and Preliminary Data Supporting Hypothesis-driven Prospective Clinical Trial Development
M. Fuss, J. Schwartz, W. Naugler, J. Urquhart, S. Orloff, K. Billingsley, G. Vaccaro, B. Koslin, K. Kolbeck, J. Kaufman Oregon Health & Science University, Portland, OR Purpose/Objective(s): International treatment algorithms and seminal review articles or textbook chapters currently do not include external beam radiation therapy options for HCC in light of a lack of prospective trial data. Nonetheless, resection margin failure after anatomic liver resection, considerable local recurrence rates after liver directed interventional radiology (IR) procedures, lack of safe IR treatment options for select patients, and tumor progression rates while waiting for potentially curative organ liver transplant provide rationale for exploring focal external-beam radiation concepts such as SBRT. Suggested primary endpoint of Phase 2 prospective trails include time to recurrence, and time to progression, with survival and time to local recurrence as secondary endpoints. Materials/Methods: We will present the Oregon Health & Science University (OHSU) institutional algorithm for treatment of early and intermediate stage HCC. Based on this algorithm, 81 patients with early or intermediate stage HCC have been treated by heterogeneously prescribed hypofractionated radiation therapy (HFxRT to 45 Gy in 18 fractions, n = 30, or SBRT to 50 Gy in 5 fractions, n = 51) since 2007. Most patients were treated in a multi-modality approach following transarterial chemoembolization (TACE) (n = 53). Other patients were treated for local failure after prior RFA, surgical margin recurrence, or lack of alternate treatment option. Results: We will present safety data for HFxRT and SBRT for HCC including toxicity mandated treatment abortion in 2 patients (both HFxRT), transient liver failure in 5 patients, and a 90 day mortality rate of 2.5%, respectively. With respect to liver function after HFxRT and SBRT, data on changes of Model of End-stage Liver Disease (MELD) score, and Child Turcotte Pugh (CTP) class are reported. Based on favorable local control in the tumors treated of 93% for HFxRT, and 96% for SBRT at a median and maximum follow-up of 10 and 43 months, and pathologic tumor response in patients that underwent liver transplant following SBRT (n = 9, with small volume viable tumor observed in only 1 patient transplanted within 6 weeks of completion of SBRT), a prospective Phase 2 randomized trial has been developed. This trial will compare TACE as the standard of care for intermediate stage HCC with TACE followed by SBRT. Conclusions: We will present background data, institutional outcomes, trial design, and rationale of TACE using Ethiodol as the embolization agent to facilitate SBRT image-guidance. The data presented should provide guidance for the development of other clinical trials assessing the role of external beam radiation therapy for HCC. Author Disclosure: M. Fuss: B. Research Grant; Varian Medical Systems. D. Speakers Bureau/Honoraria; Varian Medical Systems, BrainLab, Philips Medical Systems and Nucletron. J. Schwartz: None. W. Naugler: None. J. Urquhart: None. S. Orloff: None. K. Billingsley: None. G. Vaccaro: None. B. Koslin: None. K. Kolbeck: None. J. Kaufman: None.
1030
Assessment of Liver Function after Irradiation by MR-derived Portal Venous Perfusion Imaging
1
Y. Cao , H. Wang1, M. Feng1, T. Johnson1, T. Chenevert1, H. Hussain1, D. Normolle2, E. Ben-Josef1, R. Ten Haken1, T. S. Lawrence1 1
University of Michigan, Ann Arbor, MI, 2University of Pittsburgh, Pittsburg, PA
Purpose/Objective(s): Liver toxicity is a limiting factor for safely delivering high-dose radiation treatments for intrahepatic cancers. Radiation induced liver disease occurs weeks to months after the completion of RT. Previously, we have developed a CTbased regional venous perfusion and local dose model for prediction of liver function after irradiation. We hypothesized that liver function could be assessed individually and spatially using volumetric dynamic contrast enhanced MRI (DCE-MRI) before, during and after RT; and that the residual functioning volumes of the liver assessed by perfusion imaging would predict the overall liver function. Materials/Methods: Sixteen patients with intrahepatic cancer undergoing focal radiation therapy (median bio-dose of 58.5 Gy) were enrolled on institutional review board-approved prospective studies which obtained DCE-MRI (to measure regional perfusion) and indocyanine green (ICG) clearance rates (to measure overall liver function) prior to, during, and one and two months after treatment. The volumetric distribution of portal venous perfusion in the whole liver was estimated using in-house developed analysis tools. We determined the dose response of regional portal venous perfusion during and after RT using a linear mixed effects model. We assessed the correlation between the mean portal venous perfusion in the residual functioning volume of the liver (i.e., those showing portal venous perfusion) and overall liver function measured by ICG-before, during and after RT. Results: Reduction in regional venous perfusion one month after RT is predicted by the locally accumulated biologically-corrected dose at the end of RT (p \ 0.0.002). The regional portal venous perfusion measured during the middle of the course of RT is a significant predictor for regional venous perfusion assessed one month after RT (p \ 0.00001), indicating individual
1027
Long-term Outcomes of Neoadjuvant Chemotherapy (NC) before Chemoradiation (CRT) for Locally Advanced Pancreatic Cancer (LAPC)
N. D. Arvold1, D. P. Ryan2, A. Niemierko2, L. S. Blaszkowsky2, E. L. Kwak2, J. Y. Wo2, J. N. Allen2, R. C. Wadlow2, C. Fernandez-del Castillo2, T. S. Hong2 1
Harvard Radiation Oncology Program, Boston, MA, 2Massachusetts General Hospital, Boston, MA
Purpose/Objective(s): NC for patients with LAPC has been suggested as a means of selecting patients who will most benefit from CRT, but optimal management remains controversial and prior reports have had limited follow-up. Materials/Methods: We examined 70 consecutive patients with unresectable (n = 46) or borderline resectable (n = 24) LAPC treated with CRT at the Massachusetts General Hospital between July 2005 and November 2009. Patients typically received a radiation dose of 50.4 Gy in 1.8 Gy daily fractions (91%) with concurrent infusional 5-fluorouracil (84%) or capecitabine (14%). Forty patients (57%) received CRT alone, and 30 patients (43%) received NC before CRT (C-CRT) for a median of 4 months. NC was gemcitabine-based in 93% of patients, and all patients without progression after chemotherapy were offered CRT. Kaplan-Meier actuarial progression-free survival (PFS) and overall survival (OS) were estimated, groups were compared with log-rank tests, and Cox proportional hazard multivariate analysis (MVA) was used to analyze factors associated with PFS and OS. Results: Median age at diagnosis was 63 years and ECOG performance status score was 0 – 1 among 97% of patients. Median tumor size was 29 mm and 35 mm, and median CA 19 and 9 at presentation was 314 and 98, for the CRT and C-CRT groups, respectively. Fifty-three percent of patients in the CRT group were considered to have categorically unresectable tumors at diagnosis vs. 83% in the C-CRT group. After completion of CRT, 20% of patients were able to undergo surgical resection in the CRT group vs. 20% in the C-CRT group. Twenty-three percent of patients in the CRT group received intra-operative RT vs. 27% in the C-CRT group, to a median dose of 20 Gy (CRT) or 17 Gy (C-CRT), and adjuvant gemcitabine-based chemotherapy was received by 53% of patients in the CRT group vs. 37% in the C-CRT group. Median follow-up since diagnosis was 14.2 months. Median OS and PFS were 12.4 months and 6.7 months, respectively, in the CRT group and 18.7 months and 11.4 months in the C-CRT group (both p = 0.02). On MVA, receipt of NC (adjusted hazard ratio [AHR] = 0.49; 95% CI, 0.28 to 0.87; p = 0.02) and surgical resection (AHR = 0.38; 95% CI, 0.17 to 0.85; p = 0.02) were associated with increased OS. On MVA, receipt of NC (AHR = 0.41; 95% CI, 0.24 to 0.70; p = 0.001) and surgical resection (AHR = 0.26; 95% CI, 0.12 to 0.56; p = 0.001) were associated with increased PFS, and CA 19 and 9 level (continuous) after CRT (AHR = 1.14; 95% CI, 1.00 to 1.29; p = 0.045) was associated with decreased PFS. Conclusions: Our findings indicate a significant overall survival advantage with the use of gemcitabine-based NC to allow the selection of patients who will derive greatest benefit from CRT. The median survival we observed with this approach is similar to median survival reported in surgical series. Author Disclosure: N.D. Arvold: None. D.P. Ryan: None. A. Niemierko: None. L.S. Blaszkowsky: None. E.L. Kwak: None. J.Y. Wo: None. J.N. Allen: None. R.C. Wadlow: None. C. Fernandez-del Castillo: None. T.S. Hong: None.
1028
Dose-volume Analysis of Predictors for Gastrointestinal Toxicity after Radiotherapy and Concurrent Fulldose Gemcitabine for Locally Advanced Pancreatic Adenocarcinoma
J. Huang, J. M. Roberson, H. Ye, D. Yan William Beaumont Hospital, Royal Oak, MI Purpose/Objective(s): To identify dosimetric predictors for the development of gastrointestinal (GI) toxicity of patients with locally advanced pancreatic adenocarcinoma (LAPC) treated with concurrent full-dose gemcitabine and radiotherapy (GemRT). Materials/Methods: From June 2002 to June 2009, 46 LAPC patients treated with definitive GemRT at William Beaumont Hospital were retrospectively analyzed. Gemcitabine was administered at 1000 mg/m2 weekly during radiotherapy (RT). Twentyeight (61%) had concurrent gemcitabine alone (G-RT); eighteen (39%) had concurrent gemcitabine with daily erlotinib of 100 mg (GE-RT). RT was involved-field to treat the gross tumor volume with 1 cm margin. Thirty patients (65%) were treated on Phase I dose-escalation protocols. Median RT dose was 36 Gy (range, 22 – 42), and median fractional dose was 2.4 Gy (range, 2 – 2.8 Gy). RT technique was either 3D-conformal RT (3D-CRT, 87%) or intensity modulated RT (IMRT, 13%). Stomach and duodenum were retrospectively contoured to determine the dose-volume histogram (DVH) parameters. Duodenum was contoured from the duodenal bulb to the ligament of Treitz. GI toxicity was defined as $ Grade 3 GI toxicity using the National Cancer Institute Common Toxicity Criteria 4.0. The follow-up time was calculated from the start time of RT to the date of death or last contact. Univariate (UVA) and multivariate analyses (MVA) using Kaplan-Meier and Cox regression models were performed to identify risk factors associated with GI toxicity. Stepwise discriminant analysis (SDA) was used to determine the best DVH parameter to predict for GI toxicity.
S169
I. J. Radiation Oncology d Biology d Physics
S170
Volume 81, Number 2, Supplement, 2011
Results: After a median follow-up of 10.4 months (20.9 months for surviving patients), there were a total of 20 Grade-3 GI events among 17 patients. Actuarial Grade 3 GI toxicity rates were 26% at 3 months, 29% at 6 months, and 37% at 12 months. On UVA, only V20-35Gy of duodenum were significantly associated with GI toxicity (all p # 0.05). On MVA, V25Gy of duodenum and the use of erlotinib were independent risk factors for GI toxicity (p = 0.006 and 0.02, respectively). For the entire cohort, V25Gy of duodenum is the best predictor for GI toxicity (sensitivity = 52%, specificity = 71%, and accuracy = 59%), and the 12-month GI toxicity rate was 19% if V25Gy # 70% vs. 57% if V25Gy . 70% (p = 0.03). However, for the G-RT subset, V35Gy is the best predictor (sensitivity = 68%, specificity = 56%, and accuracy = 64%), and the 12-month GI toxicity rate was 10% if V35Gy # 25% vs. 42% if V35Gy . 25% (p = 0.06). Conclusions: DVH parameters of duodenum may be used to predict the development of Grade 3 GI toxicity after GemRT for LAPC. Concurrent use of erlotinib during GemRT may increase the risk of GI toxicity. Author Disclosure: J. Huang: None. J.M. Roberson: None. H. Ye: None. D. Yan: None.
1029
Stereotactic Body Radiation Therapy (SBRT) for Hepatocellular Carcinoma (HCC): Rationale and Preliminary Data Supporting Hypothesis-driven Prospective Clinical Trial Development
M. Fuss, J. Schwartz, W. Naugler, J. Urquhart, S. Orloff, K. Billingsley, G. Vaccaro, B. Koslin, K. Kolbeck, J. Kaufman Oregon Health & Science University, Portland, OR Purpose/Objective(s): International treatment algorithms and seminal review articles or textbook chapters currently do not include external beam radiation therapy options for HCC in light of a lack of prospective trial data. Nonetheless, resection margin failure after anatomic liver resection, considerable local recurrence rates after liver directed interventional radiology (IR) procedures, lack of safe IR treatment options for select patients, and tumor progression rates while waiting for potentially curative organ liver transplant provide rationale for exploring focal external-beam radiation concepts such as SBRT. Suggested primary endpoint of Phase 2 prospective trails include time to recurrence, and time to progression, with survival and time to local recurrence as secondary endpoints. Materials/Methods: We will present the Oregon Health & Science University (OHSU) institutional algorithm for treatment of early and intermediate stage HCC. Based on this algorithm, 81 patients with early or intermediate stage HCC have been treated by heterogeneously prescribed hypofractionated radiation therapy (HFxRT to 45 Gy in 18 fractions, n = 30, or SBRT to 50 Gy in 5 fractions, n = 51) since 2007. Most patients were treated in a multi-modality approach following transarterial chemoembolization (TACE) (n = 53). Other patients were treated for local failure after prior RFA, surgical margin recurrence, or lack of alternate treatment option. Results: We will present safety data for HFxRT and SBRT for HCC including toxicity mandated treatment abortion in 2 patients (both HFxRT), transient liver failure in 5 patients, and a 90 day mortality rate of 2.5%, respectively. With respect to liver function after HFxRT and SBRT, data on changes of Model of End-stage Liver Disease (MELD) score, and Child Turcotte Pugh (CTP) class are reported. Based on favorable local control in the tumors treated of 93% for HFxRT, and 96% for SBRT at a median and maximum follow-up of 10 and 43 months, and pathologic tumor response in patients that underwent liver transplant following SBRT (n = 9, with small volume viable tumor observed in only 1 patient transplanted within 6 weeks of completion of SBRT), a prospective Phase 2 randomized trial has been developed. This trial will compare TACE as the standard of care for intermediate stage HCC with TACE followed by SBRT. Conclusions: We will present background data, institutional outcomes, trial design, and rationale of TACE using Ethiodol as the embolization agent to facilitate SBRT image-guidance. The data presented should provide guidance for the development of other clinical trials assessing the role of external beam radiation therapy for HCC. Author Disclosure: M. Fuss: B. Research Grant; Varian Medical Systems. D. Speakers Bureau/Honoraria; Varian Medical Systems, BrainLab, Philips Medical Systems and Nucletron. J. Schwartz: None. W. Naugler: None. J. Urquhart: None. S. Orloff: None. K. Billingsley: None. G. Vaccaro: None. B. Koslin: None. K. Kolbeck: None. J. Kaufman: None.
1030
Assessment of Liver Function after Irradiation by MR-derived Portal Venous Perfusion Imaging
1
Y. Cao , H. Wang1, M. Feng1, T. Johnson1, T. Chenevert1, H. Hussain1, D. Normolle2, E. Ben-Josef1, R. Ten Haken1, T. S. Lawrence1 1
University of Michigan, Ann Arbor, MI, 2University of Pittsburgh, Pittsburg, PA
Purpose/Objective(s): Liver toxicity is a limiting factor for safely delivering high-dose radiation treatments for intrahepatic cancers. Radiation induced liver disease occurs weeks to months after the completion of RT. Previously, we have developed a CTbased regional venous perfusion and local dose model for prediction of liver function after irradiation. We hypothesized that liver function could be assessed individually and spatially using volumetric dynamic contrast enhanced MRI (DCE-MRI) before, during and after RT; and that the residual functioning volumes of the liver assessed by perfusion imaging would predict the overall liver function. Materials/Methods: Sixteen patients with intrahepatic cancer undergoing focal radiation therapy (median bio-dose of 58.5 Gy) were enrolled on institutional review board-approved prospective studies which obtained DCE-MRI (to measure regional perfusion) and indocyanine green (ICG) clearance rates (to measure overall liver function) prior to, during, and one and two months after treatment. The volumetric distribution of portal venous perfusion in the whole liver was estimated using in-house developed analysis tools. We determined the dose response of regional portal venous perfusion during and after RT using a linear mixed effects model. We assessed the correlation between the mean portal venous perfusion in the residual functioning volume of the liver (i.e., those showing portal venous perfusion) and overall liver function measured by ICG-before, during and after RT. Results: Reduction in regional venous perfusion one month after RT is predicted by the locally accumulated biologically-corrected dose at the end of RT (p \ 0.0.002). The regional portal venous perfusion measured during the middle of the course of RT is a significant predictor for regional venous perfusion assessed one month after RT (p \ 0.00001), indicating individual