Radiotherapy Enhances Efficacy of PD-1 inhibitors in Advanced Liver Cancer: A Real-world Data

doi:10.21203/rs.3.rs-2317178/v1

Background

To address the need for immunotherapy in patient with advanced primary liver cancer, combination with radiotherapy (RT) has emerged as a promising strategy. In preclinical studies, irradiated tumors released tumor antigens to synergistically increase the antitumor effect of immunotherapy. Hence, we investigated whether RT enhances efficacy of anti-programmed death receptor-1 (PD-1) inhibitor in advanced liver cancer in real world practice.

Methods

Between August 2018 and June 2021, 180 patients with advanced primary liver cancer were enrolled, 87 were treated with a combination of RT and the inhibitor of programmed death receptor (RT-PD1 cohort) and 93 were administered anti-PD-1 therapy (PD1 cohort). The first cycle of PD-1 inhibitors was administered within 60 days or concurrently with RT. Propensity score matching for bias reduction was used to evaluate the clinical outcomes.

Results

Among 49 propensity-matched pairs after PSM, median progression-free survival was 8.1 months in the RT-PD1 cohort versus 3.0 months in the PD1 cohort (P < 0.001). Median overall survival was 21.7 months in the RT-PD1 cohort versus 13.3 months in the PD1 cohort (P = 0.023). Compared with patients in the PD1 cohort, patients in the RT-PD1 cohort had a significantly higher objective response rates (49.0% versus 22.4%, P = 0.006) and disease control rates (71.4% versus 32.7%, P < 0.001). The incidences of toxic effects were not significantly different between the two cohorts.

Conclusions

RT plus anti-PD-1 therapy is well tolerated. RT enhances the efficacy of anti-PD-1 therapy in patients with advanced liver cancer by improving survival outcomes without increased toxic effects.

Radiation therapy

immune checkpoint inhibitor

programmed cell death-1

liver cancer

The success of immune checkpoint inhibitors (ICIs) represented by programmed death receptor/ligand-1 (PD-1/PD-L1) antibodies has opened a new era of advanced liver cancer treatment^1–3. However, primary resistance of ICIs exposes patients to ineffective treatment, possibly because certain tumor antigens are not detected. As the mechanisms of acquired resistance to ICIs remain unknown, only a subset of patients responds and presents long-term clinical benefits, leaving the need to investigate further options for non-responders⁴. Therefore, research efforts are being focused on various combined approaches to improve treatment outcomes. It is well documented that radiotherapy (RT) enhances the immune response in this setting.

Radiotherapy can reshape the liver tumor microenvironment to prevent antigen-specific T cell loss⁹. In preclinical studies, irradiated tumors released more tumor antigens, presented antigens more effectively, and had higher T-cell infiltration. Combining RT with ICIs generated a further shrinkage of tumor in several solid tumor types compared with either of these treatments alone^5–8. ICIs combined with local precision RT for advanced liver cancer may be a strategy to circumvent the primary or acquired resistance to ICIs, and further optimize the efficacy of therapy¹⁰. A previous study suggested that the priming effect of RT can rescue the immune response and resistance to ICIs in poor immunogenicity tumors¹¹. Importantly, the administration of PD-1 inhibitors during RT reduces the aggregation of myeloid-derived suppressor cells and enhances the antitumor effects of CD8⁺ T cells that further help improve efficacy of RT¹². Our recent published study showed that PD-L1 expression in liver cancer cells increases after RT to enhances ICIs efficacy¹³, which reflected RT can enhance response to ICIs and synergistically augment the antitumor effect^12,14,15.

Despite this, there is no published prospective clinical data on combined RT and anti-PD-1 therapy in advanced liver cancer, except a few small series^16–18, which were limited to the detection of potentially significant differences in response rates and outcomes when analyzed individually. In this study, we presented the real-world evidence to illustrate the efficacy and safety of RT plus anti-PD-1 therapy compared to anti-PD-1 monotherapy in advanced primary liver cancer.

Patients

This retrospective study enrolled 180 patients initially diagnosed with advanced primary hepatocellular carcinoma (HCC) or intrahepatic cholangiocarcinoma (ICC) according to the American Joint Committee on Cancer standards. The Institutional Review Board of Zhongshan Hospital of Fudan University, Shanghai, China approved this retrospective study (No. B2021-828R2) with waiver of informed consent.

Patients with a previous liver transplant, active autoimmune liver disease or other malignant tumors were excluded. Patients received targeted therapy comprising VEGF blockade and other anti-angiogenic drugs administered concurrently with anti-PD-1 therapy. Patients infected with hepatitis B virus (HBV) were treated with antiviral therapy prior to anti-PD-1 therapy.

Patients who received RT plus anti-PD-1 therapy (RT-PD1 cohort) or anti-PD-1 therapy alone (PD1 cohort) between August 2018 and June 2021 were included in the study. Propensity score matching (PSM) was performed using a nearest-neighbor algorithm with a caliper of width equal to 0.2 in a 1:1 ratio according to Eastern Cooperative Oncology Group (ECOG) score, sex, age (< 50 vs. ≥50 years), HBV infection status, Child-Pugh score, extrahepatic metastasis, macroscopic vascular invasion, tumor size, alpha-fetoprotein level, histology (HCC vs. ICC), and targeted agents between the two groups to minimize bias caused by non-randomized selection of patients. After PSM, 49 matched pairs were identified.

Radiotherapy And Immunotherapy

The RT-PD1 cohort was defined as the first cycle of PD-1 inhibitors administered within 60 days or concurrently with RT. For RT planning, according to guidelines of the Chinese Society of Clinical Oncology¹⁹, the vacuum immobilization bag was used to active respiratory control was maintained to reduce liver range of motion, including tomotherapy intensity-modulated radiotherapy (TOMO-IMRT) or stereotactic body radiotherapy (SBRT). TOMO-IMRT was delivered at a total dose of 28.0–60.0 Gy at 1.6–6.0 Gy per fraction in 44 cases (50.6%). SBRT was delivered at a total dose of 30.0–60.0 Gy at 5.0–10.0 Gy per fraction in 43 cases (49.4%).

Images were contrasted on a 4D computed tomography (4D-CT) simulator through abdominal compression to evaluate the liver motion and determine internal target volume. Mega-Voltage CT was acquired prior to each course. The largest tumor was selected as the target-lesion for radiotherapy, and up to three nodules were allowed under the condition that the tolerated dose was delivered to the liver.

Response And Safety Assessment

According to the Response Evaluation Criteria in Solid Tumors (RECIST 1.1), tumor response was assessed every 2 to 3 months by two independent radiologists through dynamic contrast-enhanced CT or MRI. Complete response (CR) was determined as complete disappearance of all tumors; partial response (PR) and progressive disease (PD) were defined as > 30% decrease and > 20% increase in the sum of the largest diameters of total tumors, respectively; and stable disease (SD) was defined as neither PR nor PD. The appearance of new lesions was considered as PD. The objective response rate (ORR) was defined as a sum of CR and PR, and disease control rate (DCR) was defined as sum of CR, PR, and SD. The best out-of-field (abscopal) rate was defined only in non-irradiated lesions.

Adverse events (AEs) were determined according to the Common Terminology Criteria for Adverse Events (CTCAE v5.0). We assessed the development and severity of representative AEs at regular follow-up visits until 30 days after treatment cessation, including, decreased appetite, fever, diarrhea, fatigue, nausea, myalgia, thrombocytopenia, leukopenia, hypothyroidism, hepatitis, myocarditis, pneumonitis, rash, and hypoadrenocorticism.

Statistical Analysis

Categorical parameters are expressed as numbers and percentages and compared using χ² or Fisher’s exact test. Progression-free survival (PFS) was measured from the start of RT to date of progression or death due to any cause, or last follow-up. Overall survival (OS) was calculated as the interval between the initiation of RT until death due to any cause, or last follow-up. Log-rank tests were performed on Kaplan-Meier survival curves from treatment to PFS and OS. Prognostic factors were evaluated by univariate and multivariate Cox proportional hazard regression. The hazard ratios (HRs) and 95% confidence intervals (CIs) were presented. PSM and statistical analyses were performed using SPSS 26.0 (SPSS Inc., Chicago, IL, USA) and R software version 4.1.0 (R Core Team, Vienna, Austria). A P < 0.05 was considered to be statistically significant.

Baseline Characteristics Of Rt- Pd1 Therapy And Anti-pd-1 Therapy

Of the 180 patients, 87 were in the RT-PD1 cohort and 93 in the PD1 cohort. A total of 136 (75.56%) were diagnosed with HCC, 119 (66.1%) were infected with HBV, 115 (63.89%) received targeted therapy, and 123 (68.33%) had extrahepatic metastasis. Seventeen patients (9.4%) received first-line therapy, and 83 patients (90.6%) received second-line or later therapy (Table 1). Of the Anti-PD-1 antibodies, nivolumab, pembrolizumab, camrelizumab, tislelizumab, toripalimab and sintilimab were administered in 15, 30, 40, 47, 15 and 33 patients, respectively.

Table 1

Patients' baseline demographic characteristics before and after PSM.
	Before matching			After matching
	Overall	RT + PD1	PD1	Overall	RT + PD1	PD1	p-value
Variable, No. (%)	(n = 180)	(n = 87)	(n = 93)	(n = 94)	(n = 49)	(n = 49)
Sex
Male	148(82.22)	78(89.66)	70(75.27)	12(12.77)	5(10.20)	7(14.29)	0.538
Female	32(17.78)	9(10.34)	23(24.73)	86(91.49)	44(89.80)	42(85.71)
Age(years)
<50	52(28.89)	29(33.33)	23(24.73)	25(26.60)	14(28.57)	11(22.45)	0.487
≥50	128(71.11)	58(66.67)	70(75.27)	73(77.66)	35(71.43)	38(77.55)
HBV
Without	61(33.89)	32(36.78)	29(31.18)	29(30.85)	15(30.61)	14(28.57)	0.825
With	119(66.11)	55(63.22)	64(68.82)	69(73.40)	34(69.39)	35(71.43)
Child-Pugh grade
A	150(83.33)	80(91.95)	70(75.27)	81(86.17)	42(85.71)	39(79.59)	0.424
B	30(16.67)	7(8.05)	23(24.73)	17(18.09)	7(14.29)	10(20.41)
ECOG performance status
0	32(17.78)	23(26.44)	9(9.68)	19(20.21)	12(24.49)	7(14.29)	0.201
1	148(82.22)	64(73.56)	84(90.32)	79(84.04)	37(75.51)	42(85.71)
Extrahepatic metastasis
Without	57(31.67)	28(32.18)	29(31.18)	32(34.04)	17(34.69)	15(30.61)	0.667
With	123(68.33)	59(67.82)	64(68.82)	66(70.21)	32(65.31)	34(69.39)
Macroscopic vascular invasion
Without	129(71.67)	79(90.80)	50(53.76)	82(87.23)	43(87.76)	39(79.59)	0.274
With	51(28.33)	8(9.20)	43(46.24)	16(17.02)	6(12.24)	10(20.41)
Tumor size(mm)
<50	109(60.56)	69(79.31)	40(43.01)	71(75.53)	37(75.51)	34(69.39)	0.498
≥50	71(39.44)	18(20.69)	53(56.99)	27(28.72)	12(24.49)	15(30.61)
AFP (ng/mL)
<400	125(69.44)	70(80.46)	55(59.14)	72(76.60)	38(77.55)	34(69.39)	0.36
≥400	55(30.56)	17(19.54)	38(40.86)	26(27.66)	11(22.45)	15(30.61)
Histology
HCC	136(75.56)	59(67.82)	77(82.80)	81(86.17)	41(83.67)	40(81.63)	0.79
ICC	44(24.44)	28(32.18)	16(17.20)	17(18.09)	8(16.33)	9(18.37)
Targeted medicine
Without	65(36.11)	41(47.13)	24(25.81)	34(36.17)	20(40.82)	14(28.57)	0.203
With	115(63.89)	46(52.87)	69(74.19)	64(68.09)	29(59.18)	35(71.43)
Previous therapy
No	17(9.4)	10(11.5)	7(7.5)	10(10.6)	7(14.3)	3(6.1)	0.122
Resection	57(31.7)	33(37.9)	24(25.8)	45(47.9)	28(57.1)	17(34.7)
Ablation	34(18.9)	13(14.9)	21(22.6)	19(20.2)	7(14.3)	12(24.5)
TACE	135(75)	60(69)	75(80.6)	72(76.6)	33(67.3)	39(79.6)
Systemic chemotherapy	12(6.7)	4(4.6)	8(8.6)	6(6.4)	2(4.1)	4(8.2)
PSM, propensity score matching; RT, radiation therapy; PD1, anti-programmed death receptor-1 inhibitor; ECOG, Eastern Cooperative Oncology Group;
AFP, alpha fetoprotein; HCC, hepatocellular carcinoma; ICC, intrahepatic cholangiocarcinoma; TACE, transcatheter arterial chemoembolization.

The median time between immunotherapy and radiation was 7 days (range 0–60 days). The tumor sites selected for RT were primarily liver lesions. The median radiation dose delivered was 4 Gy (1.6–10 Gy). The patients received radiotherapy approach were SBRT (n = 44) and TOMO-IMRT (n = 43). Nineteen patients received palliative RT and 68 patients received RT for local control. The details of the radiotherapy treatment regimens are displayed in Table E1. After performing PSM, we obtained one-to-one matching cohorts (49 patients per group) for the RT-PD1 cohort vs. PD1 cohort (Table 1). The baseline variables between the matched cohorts were not found significant differences.

Comparison Of Tumor Responses Between The Groups

According to imaging assessment, the ORR was 47.1% and 20.4% in the RT-PD1 and PD1 cohorts, respectively (P < 0.001). The DCR was also significantly higher in the RT-PD1 cohort than in PD1 cohort (72.4% vs. 33.3%; P < 0.001). After performing PSM, compared with patients in the PD1 cohort, patients in the RT-PD1 cohort had a significantly higher objective response rates (49.0% versus 22.4%, P = 0.006; Table 2) and disease control rates (71.4% versus 32.7%, P < 0.001; Table 2).

Table 2

Comparison of efficacy of RT-PD1 group with PD1 group based on tumor response before and after PSM.
	Before matching				After matching
	Overall (n = 180)	RT + PD1 (n = 87)	PD1 (n = 93)	p-value	Overall (n = 94)	RT + PD1 (n = 49)	PD1 (n = 49)	p-value
Tumor response, No. (%)				< 0.001				< 0.001
Complete response	6 (3.3)	5 (5.7)	1 (1.1)		4 (4.3)	2 (4.1)	0 (0)
Partial response	54 (30)	36 (41.4)	18 (19.4)		26 (27.7)	22 (44.9)	11 (22.4)
Stable disease	34 (18.9)	22 (25.3)	12 (12.9)		17 (18.1)	11 (22.4)	5 (10.2)
Progressive disease	86 (47.8)	24 (27.6)	62 (66.7)		47 (50)	14 (28.6)	33 (67.3)
Response rate, %
ORR	33.3	47.1	20.4	< 0.001	31.9	49.0	22.4	0.006
DCR	52.2	72.4	33.3	< 0.001	50.0	71.4	32.7	< 0.001
RT, radiation therapy; PD1, anti-programmed death receptor-1 inhibitor; PSM, propensity score matching;
ORR, objective response rate; DCR, disease control rate

Comparison Of Survival Outcomes Between The Groups

Median PFS in the RT-PD1 cohort was higher than that in PD1 cohort (8.1 vs. 2.9 months; P < 0.001, Fig. 1A). Median PFS was significantly different between the RT-PD1 cohort and PD1 cohort after performing PSM (8.1 and 3.0 months, respectively; P < 0.001, Fig. 1B).

The multivariate analysis using Cox regression model indicated that RT-PD1 treatment (HR: 0.442; 95% CI: 0.294–0.668; P < 0.001) and Child-Pugh score (HR: 1.616; 95% CI: 1.024–2.549; P = 0.039) were independent prognostic factors for PFS in the unmatched cohorts (Table 3). The multivariate analysis also showed that RT-PD1 treatment was the only independent prognostic factor for PFS in the matched cohorts (HR: 0.450; 95% CI: 0.285–0.708; P < 0.001; Table 3).

Table 3

Prognostic factors affecting progression-free survival of patients using univariable and multivariable analyses before and after PSM.
	Before matching						After matching
	Univariable			Multivariable			Univariable			Multivariable
Variable	HR	95%CI	p-value	HR	95%CI	p-value	HR	95%CI	p-value	HR	95%CI	p-value
Sex
Female	1 (ref)						1 (ref)
Male	1.325	0.868–2.024	0.192				1.231	0.648–2.336	0.526
Age(years)
<50	1 (ref)						1 (ref)
≥50	1.21	0.846–1.731	0.295				1.054	0.633–1.756	0.840
HBV
Without	1 (ref)						1 (ref)
With	1.105	0.771–1.583	0.588				1.295	0.777–2.158	0.321
Child-Pugh grade
A	1 (ref)			1 (ref)			1 (ref)
B	1.787	1.146–2.787	0.010	1.616	1.024–2.549	0.039	1.303	0.715–2.375	0.387
ECOG performance status
0	1 (ref)			1 (ref)			1 (ref)
1	2.128	1.307–3.464	0.002	1.261	0.622–2.556	0.519	1.819	0.978–3.384	0.059
Extrahepatic metastasis
Without	1 (ref)			1 (ref)			1 (ref)			1 (ref)
With	1.521	1.055–2.193	0.025	1.190	0.697–2.031	0.524	1.780	1.078–2.94	0.024	1.464	0.848–2.526	0.171
Macroscopic vascular invasion
Without	1 (ref)			1 (ref)			1 (ref)
With	1.687	1.171–2.43	0.005	1.014	0.636–1.615	0.954	1.187	0.653–2.161	0.574
Tumor size(mm)
<50	1 (ref)			1 (ref)			1 (ref)
≥50	1.731	1.228–2.44	0.002	1.083	0.716–1.640	0.705	1.355	0.811–2.265	0.246
AFP (ng/mL)
<400	1 (ref)			1 (ref)			1 (ref)			1 (ref)
≥400	1.716	1.211–2.433	0.002	1.265	0.851–1.879	0.245	1.873	1.142–3.070	0.013	1.524	0.891–2.606	0.124
Histology
HCC	1 (ref)						1 (ref)
ICC	0.857	0.581–1.263	0.435				0.791	0.433–1.446	0.446
Treatment
PD1	1 (ref)			1 (ref)			1 (ref)			1 (ref)
RT + PD1	0.382	0.271–0.537	< 0.001	0.442	0.294–0.668	< 0.001	0.432	0.275–0.681	< 0.001	0.450	0.285–0.708	< 0.001
Targeted medicine
Without	1 (ref)			1 (ref)			1 (ref)
With	1.487	1.045–2.115	0.027	1.071	0.724–1.586	0.731	1.447	0.896–2.338	0.131
PSM, propensity score matching; ECOG, Eastern Cooperative Oncology Group; AFP, alpha fetoprotein; HCC, hepatocellular carcinoma; ICC, intrahepatic cholangiocarcinoma; RT, radiation therapy; PD1, anti-programmed death receptor-1 inhibitor

The median follow-up duration was 19.5 months (95% CI: 16.247–22.753) in the two cohorts. During the follow-up period, 94 (52.2%) of the 180 patients died (26 [29.8%] and 68 [73.1%] patients in the RT-PD1 and PD1 cohorts, respectively). The median OS was significantly longer in the RT-PD1 cohort than that in PD1 cohort (22.7 vs. 8.3 months; P < 0.001; Fig. 2A). Median OS was also significantly different between the RT-PD1 and PD1 cohorts after PSM (21.7 and 13.3 months, respectively; P = 0.023; Fig. 2B).

The multivariate analysis suggested that RT-PD1 treatment (HR: 0.534; 95% CI: 0.317–0.900; P = 0.018) and Child-Pugh score (HR: 1.726; 95% CI: 1.049–2.841; P = 0.032) were independent prognostic factors for OS in the unmatched cohorts (Table 4). Moreover, RT-PD1 treatment (HR: 0.530; 95% CI: 0.287–0.976; p = 0.042), men (HR: 2.345; 95% CI: 1.106–4.970; P = 0.026), and extrahepatic metastasis (HR: 2.047; 95% CI: 1.000–4.191; P = 0.050) were independent prognostic factors for OS in the matched cohorts (Table 4).

Table 4

Prognostic factors affecting overall survival of patients using univariable and multivariable analyses before and after PSM.
	Before matching						After matching
	Univariable			Multivariable			Univariable			Multivariable
Variable	HR	95%CI	p-value	HR	95%CI	p-value	HR	95%CI	p-value	HR	95%CI	p-value
Sex
Female	1 (ref)						1 (ref)			1 (ref)
Male	1.548	0.951–2.520	0.079				2.095	1.008–4.352	0.047	2.343	1.106–4.967	0.026
Age(years)
<50	1 (ref)						1 (ref)
≥50	1.477	0.962–2.269	0.075				1.458	0.793–2.681	0.225
HBV
Without	1 (ref)						1 (ref)
With	1.011	0.652–1.567	0.961				1.283	0.667–2.467	0.455
Child-Pugh grade
A	1 (ref)			1 (ref)			1 (ref)
B	2.371	1.477–3.805	< 0.001	1.726	1.049–2.841	0.032	1.858	0.967–3.572	0.063
ECOG performance status
0	1 (ref)						1 (ref)
1	3.319	1.535–7.176	0.065				3.234	1.161–9.008	0.065
Extrahepatic metastasis
Without	1 (ref)						1 (ref)			1 (ref)
With	1.570	0.986–2.502	0.058				2.134	1.088–4.187	0.027	2.047	1.000-4.191	0.050
Macroscopic vascular invasion
Without	1 (ref)			1 (ref)			1 (ref)
With	2.413	1.597–3.647	< 0.001	1.512	0.945–2.418	0.085	1.121	0.559–2.249	0.748
Tumor size(mm)
<50	1 (ref)			1 (ref)			1 (ref)
≥50	2.048	1.365–3.071	0.001	1.309	0.832–2.062	0.244	1.402	0.771–2.550	0.268
AFP (ng/mL)
<400	1 (ref)			1 (ref)			1 (ref)			1 (ref)
≥400	1.653	1.091–2.505	0.018	1.180	0.764–1.822	0.457	1.820	1.009–3.284	0.047	1.345	0.721–2.507	0.352
Histology
HCC	1 (ref)						1 (ref)
ICC	0.72	0.452–1.148	0.167				0.591	0.294–1.188	0.140
Treatment
PD1	1 (ref)			1 (ref)			1 (ref)			1 (ref)
RT + PD1	0.369	0.234–0.582	< 0.001	0.534	0.317-0.900	0.018	0.503	0.275–0.921	0.026	0.530	0.287–0.976	0.042
Targeted medicine
Without	1 (ref)						1 (ref)
With	1.146	0.738–1.779	0.543				0.814	0.45–1.47	0.494
PSM, propensity score matching; ECOG, Eastern Cooperative Oncology Group; AFP, alpha fetoprotein; HCC, hepatocellular carcinoma; ICC, intrahepatic cholangiocarcinoma; RT, radiation therapy; PD1, anti-programmed death receptor-1 inhibitor

Given the difference in clinical profiles between HCC and ICC, we further assessed the survival outcomes between the groups in HCC patients (Table E2, n = 136). Compared with patients in the PD1 cohort, median PFS and OS in the RT-PD1 cohort were significantly longer (PFS: 9.9 vs. 3.0 months, P < 0.001; OS: not reached vs. 10.2 months, P < 0.001; Fig. E1).In the matched cohorts, PFS and OS in the RT-PD1 cohort were also significantly longer than PD1 cohort (PFS: 8.7 vs. 3.2 months, P < 0.001; OS: not reached vs. 13.3 months, P = 0.016; Fig. E2). However, we did not analyze the survival outcomes between the groups in ICC patients as the small sample size after performing PSM (n = 17) may limit the statistical power of the test.

Effects Of Rt-pd1 Treatment Without Increasing Adverse Effects

The distribution of AEs before and after PSM is summarized in Table 5. Treatment-related AEs were occurred in 53 (57.0%) and 54 (62.1%) patients in the PD1and RT-PD1 cohorts, respectively. Grade 3 to 4 AEs occurred in 8 (8.6%) patients in the PD1 cohort and 8 (9.2%) in RT-PD1 cohort. The most frequent treatment-related AEs of all grades were fatigue, decreased appetite, rash and, nausea.

Table 5. Treatment-related adverse events Summary before and after PSM.

Adverse event	Before matching						After matching
	RT+PD1		PD1		p-value		RT+PD1		PD1		p-value
	(n=87)		(n=93)		p-value		(n=49)		(n=49)		p-value
	Any grade	Grade 3-4	Any grade	Grade 3-4	Any grade	Grade 3-4	Any grade	Grade 3-4	Any grade	Grade 3-4	Any grade	Grade 3-4
Decreased appetite	16(18.4)	0	18(19.1)	0	0.868	-	9(18.4)	0	12(24.5)	0	0.460	-
Fever	8(9.2)	1(1.1)	9(9.6)	0	0.973	-	5(10.2)	1(2)	5(10.2)	0	1	1
Diarrhea	2(2.3)	0	5 (5.4)	0	0.285	-	1(2)	0	4(8.2)	0	0.359	-
Fatigue	22(25.3)	0	20(21.3)	0	0.548	-	13(26.5)	0	15(30.6)	0	0.655	-
Nausea	13(14.9)	0	19(20.2)	0	0.335	-	8(16.3)	0	6(12.2)	0	0.564	-
Myalgia	5(5.8)	0	2 (2.2)	0	0.388	-	2(4.1)	0	0	0	0.475	-
Thrombocytopenia	5(5.8)	1(1.1)	5 (5.4)	2 (2.2)	0.828	0.953	3(6.1)	1(2)	2 (4.1)	0	1	1
Leukopenia	2(2.3)	0	1 (1.1)	0	0.953	-	0	0	1 (2)	0	1	-
Hepatitis	6(6.9)	2(2.3)	5 (5.4)	2 (2.2)	0.670	0.629	5(10.2)	3(6.1)	3 (6.1)	0	0.712	0.241
Hypothyroidism	5(5.8)	0	6 (6.5)	0	0.844	-	1(2)	0	6 (12.2)	0	0.117	-
Myocarditis	5(5.8)	2(2.3)	5 (5.4)	2 (2.2)	0.828	0.661	1(2)	1(2)	4 (8.2)	1 (2)	0.359	1
Pneumonitis	8(9.2)	0	5 (5.4)	0	0.323	-	3(6.1)	0	4 (8.2)	0	1	-
Rash	14(16.1)	4(4.6)	15 (16.1)	4 (4.3)	0.995	0.791	5(10.2)	0	6 (12.2)	2 (4.1)	0.749	0.475
Hypoadrenocorticism	1(1.1)	1(1.1)	2 (2.2)	0	0.953	0.973	1(2)	1(2)	2 (4.1)	0	1	1

PSM, propensity score matching; RT, radiation therapy; PD1, anti-programmed death receptor-1 inhibitor; AE, Adverse event.

Considering the pre-propensity-matched RT-PD1 and PD1 cohorts as a whole, the incidence and types of AEs were similar, most of them were grade 1 to 2 in severity, and the AE profiles were similar between the two groups. The findings before PSM were approximately the same as the results for overall population analysis after PSM.

To the best of our knowledge, this is the largest assessment of retrospective obtained data to identify an additive effect of RT on response to anti-PD-1 therapy in patients with advanced primary liver cancer. We obtained primary evidence on the superiority of RT-PD1 over anti-PD-1 therapy in terms of OS, PFS, and tumor response in the treatment of liver cancer without an increase in toxic effects caused by both RT and related immunotherapies. The credibility of these results was provided by PSM analysis that simulated randomization of a prospective study and reduced potential biases associated with confounding variables in study design.

RT synergistically enhance the antitumor effect of immunotherapy via multiple potential mechanisms, such as increasing the visibility of tumor antigens, attracting leukocytes into the tumor tissue, and modulating the tumor microenvironment^8,12,20,21. Thus, combining immunotherapy and radiotherapy is being considered as a possible way of improving clinical benefits in patients who are not responding or have become resistant to immunotherapy. Recent clinical studies suggested that combining pembrolizumab and radiotherapy improved the responses and outcomes of metastatic non-small-cell lung cancer ²². However, combination strategy is still under preclinical and clinical development for patients with liver cancer³⁵. We demonstrated that combining RT with PD-L1 blockade results in a better response in preclinical liver tumors¹³. An important concept in this regard is the abscopal effect, which reflected to generate systemic antitumor immune response at unirradiated out-of-field lesions²³. It is thought that RT increases systemic antigen release from tumor tissue, enhancing antigen recognition by antigen-presenting cells, thereby subsequently presenting antigens to T cells as a result (CD8 + cytotoxic T lymphocytes in particular). Activation of the above cells triggers both local and systemic antitumor immune responses. In addition, sublethal doses of RT have been demonstrated to attract T cells to tumors by modulating their microenvironment, while low dose RT decreases the immunosuppressive cell signaling induced by high doses^24–27.

The use of RT for local control is imperative as the out-of-field lesion can be better controlled with improved systemic therapy²³. The present analysis mainly included irradiated intrahepatic lesions and indicated the abscopal effect was induced at a much higher frequency with inclusion of RT. Of the patients with metastatic disease, > 50% (22 out of 32 patients evaluated) treated with RT-PD1 in the present study developed the best out-of-field control response (Table E3). Furthermore, levels of tumor-specific T cells increased in patients after treatment, except during RT, as described in a previous study²⁸. Therefore, we also included patients who received anti-PD-1 therapy shortly after RT (< 60 days) to minimize delay of systemic treatment that may have increased susceptibility of their immune systems to T-cell penetration and activation.

Immunotherapy therapy is a definite breakthrough in the treatment of advanced liver cancer^2,29−31. Despite this, most immunotherapy benefits have come from a subset of patients achieved a durable antitumor response, such as anti-PD-1 monoclonal antibody et al, and presented with long-term benefits from immunotherapy-based approaches^2,3. In the present study, the ORR and DCR were significantly better in the RT-PD1 cohort than those in PD1 cohort. We observed a significantly longer median OS of 21.7 months in the RT-PD1 cohort than 13.3 months in the PD1 cohort. Considering the etiological and biological heterogeneities between ICC and HCC, we further analyzed the survival outcomes between the groups of HCC patients. Surprisingly, the RT-PD1 cohort resulted in significantly longer PFS and OS than the PD1 cohort. Because of the relatively small number of patients with ICC (n = 17), the statistical power may not be sufficient for detection. Meanwhile, a study by Chiang et al. described higher ORR in five patients with unresectable, large HCC, treated with RT plus ICIs¹⁷. They further investigated 15 patients with advanced HCC who had a better prognosis after treatment with RT-ICIs than that with TACE³². In addition, treatment of a case with macroscopic vascular invasive HCC with Y-90 radioembolization plus nivolumab successfully decreased the extent of treatment to partial hepatectomy³³. These results imply that the efficacy of anti-PD-1 therapy can be improved using combination strategies with curative potential, and RT is an optimal candidate.

The optimal radiation dose and fractionation regimens for stimulating a systemic antitumor immune response remain unclear. Intriguingly, our subgroup analyses indicated that RT-PD1 with > 5Gy in 6–10 fractions resulted in significantly longest OS and PFS, and followed by RT-PD1 with < 5Gy in 10–25 fractions and PD-1 alone (Fig. E3 and E4). In the matched cohort, two patients showed a CR assessed by the RECIST after receiving > 5Gy RT in 6 fractions with anti-PD-1 therapy. Moreover, the responses were durable—both patients remained disease-free for 13.0 and 4.3 months and were still alive at 24.2 and 29 months of follow-up, respectively. Our findings are consistent with those of preclinical studies, and many line of evidence in vivo suggest that the immune-modulating effects of high dose radiations with hypofractionated RT are more pronounced than single-dose RT, leading to a better systemic response^27,34−36. However, we could not further perform PSM by the radiation dose and fractionation due to the low sample size. This observation remains striking and warrants further clinical investigation.

In the present study, the most frequent AEs associated with RT plus anti-PD-1 therapy were fatigue, decreased appetite, fever, rash and, nausea. A majority of the patients in the present study experienced grade 1–2 immune- mediated AEs. The above-mentioned AEs were reversible and manageable; and, the incidences of treatment-related toxic effects had no significant difference in both cohorts. Safety measures showed a good profile consistent with findings of previous studies on RT plus anti-PD-1 therapy^8,37−41.

Our analysis is limited by its retrospective nature, although PSM was used to mitigate potential biases associated with the study design. Second, there was heterogeneity in the study population that included patients who received radiotherapy at different times during the disease course. Third, the standard of dose fractionation regimen, target volume, and role of PD-L1 remained to be explored.

In conclusion, the study showed that RT-PD1 therapy may improve PFS and OS in patients with advanced primary liver cancer by activating systemic antitumor immune responses without increased toxic effects. A prospective randomized trial is currently underway to validate these results (ClinicalTrials.gov identifier: NCT03857815).

Acknowledgements

This abstract has been selected for an Oral presentation in 2022 American Society for Radiation Oncology Annual Meeting ⁴².

Author contributions

SJH, YCC, XHL, YH, YZ, WFH, and YXC contributed to the acquisition, analysis and interpretation of data, and statistical analysis and drafting of the manuscript. SJH, YCC, RXC, ZCZ, and SSD were responsible for the study concept and design, analysis and interpretation of the data, drafting of the manuscript, and obtaining funding and study supervision. All authors read and approved the final manuscript.

Funding support

This study was supported by National Natural Science Foundation of China (Grant No. 82073479).

Conflict of interests

The authors declare no conflict of interests.

Ethics approval

This study was approved by the Institutional Review Board of Zhongshan Hospital of Fudan University, Shanghai, China (No. B2021-828R2)

Informed consent

The written informed consent of participants was waived due to the retrospective nature of the study.

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SupplementaryMaterial.docx

Radiotherapy Enhances Efficacy of PD-1 inhibitors in Advanced Liver Cancer: A Real-world Data

Status:

Version 1

Abstract

Background

Methods

Results

Conclusions

Figures

Introduction

Methods And Materials

Patients

Radiotherapy And Immunotherapy

Response And Safety Assessment

Statistical Analysis

Results

Baseline Characteristics Of Rt- Pd1 Therapy And Anti-pd-1 Therapy

Comparison Of Tumor Responses Between The Groups

Comparison Of Survival Outcomes Between The Groups

Effects Of Rt-pd1 Treatment Without Increasing Adverse Effects

Discussion

Declarations

References

Supplementary Files

Status:

Version 1