Recurrent Intimal Sarcoma: Treatments Tried and Results

In short

There is no standard treatment for recurrent intimal sarcoma and no randomised trial. The largest dataset is 72 patients pooled from 17 reference centres.¹
Anthracycline-based chemotherapy has the best documented activity: 19 of 50 evaluable patients responded (38%). In advanced disease the median time without progression was 7.7 months.¹
Gemcitabine-based chemotherapy and pazopanib each produced a response in 8% of patients in that series. Individual patients have stayed stable on pazopanib for a year or longer.^{1, 15, 16}
The only prospective trial in this disease tested the MDM2 inhibitor milademetan: 2 of 10 patients had responses lasting more than 15 months.²
For CDK4/6 inhibitors there is no dedicated published report in intimal sarcoma. The evidence is borrowed from dedifferentiated liposarcoma.^{19, 20}
The durable responses to checkpoint inhibitors cluster in tumours with mismatch-repair deficiency (MSI-high). Outside that group the evidence is a handful of patients.^{3, 4, 5}
When recurrence is confined to one site, repeat surgery or radiotherapy appears in most reports of long survival, but these are single, selected cases.^{28, 29, 30, 31, 32}

How to read this page

Almost everything known about treatment at recurrence comes from retrospective series and single case reports. Three things follow from that.

Case reports over-represent successes. A patient who did well is far more likely to be written up than one who did not. Read "a patient responded" as "this has happened at least once", not as "this is likely".
The numbers are small and often mixed. Many surgical series combine intimal sarcoma with other sarcomas of the pulmonary artery.
Definitions vary. Older reports predate routine MDM2 testing, so some tumours called intimal sarcoma then might be classified differently today.

We give the number of patients behind every statement. Where only the abstract of a paper or a conference report was available to us, the source list says so.

How soon recurrence happens

These figures describe groups of patients treated in different ways and at different times. They are not a forecast for one person.

Series	Patients	What was reported
World Sarcoma Network, 17 centres¹	72 intimal sarcomas	Localised disease treated with curative intent: median 14.6 months without recurrence
Juntendo University, Tokyo⁶	10 intimal sarcomas of the pulmonary artery	Recurrence in 8 of 9 patients after a median of 10 months (range 3 to 19), always within the chest
China-Japan Friendship Hospital, Beijing⁷	20 patients treated by endarterectomy, 19 with intimal sarcoma	Recurrence or metastasis in 11; median 4 months without disease; median survival 26 months
Houston Methodist⁸	20 resected pulmonary artery sarcomas	Clear margins in 45%; survival from diagnosis 85% at 1 year, 49% at 3 and at 5 years, 16% at 10 years
Seven European centres⁹	84 pulmonary artery sarcomas, 39 confirmed intimal	Median 19 months without progression with combined treatment and 16 months with surgery alone; the difference was not statistically significant

No published series reports survival after recurrence as a measure of its own. It can only be pieced together from individual cases.

Chemotherapy

The best data come from the World Sarcoma Network series of 72 MDM2-positive intimal sarcomas. It pools patients with localised and advanced disease, and it is retrospective.¹

Regimen	Patients	Responses	Time without progression
Anthracycline-based (doxorubicin, often with ifosfamide)	66 treated, 42 with advanced disease; 50 evaluable	2 complete and 17 partial responses (38%)	Advanced disease: median 7.7 months; median survival 21.8 months
Gemcitabine-based (mostly as second line)	26 treated; 25 evaluable	2 partial responses (8%)	Median 3.2 months; median survival 13.1 months

Smaller series are less encouraging. In 13 patients from Leuven the median survival was 13 months, and the authors describe the disease as highly resistant to chemotherapy and targeted drugs.¹⁰ In a British series of 20 pulmonary artery sarcomas (13 intimal) the median survival was 17 months; two partial responses to chemotherapy lasted 6 and 5 months.¹¹

Later lines rest on single patients. One patient responded for 8 months to carboplatin and vinorelbine as fourth line, after gemcitabine with dacarbazine, trabectedin and pazopanib had failed.¹² In another, a large local recurrence 44 months after surgery regressed on vinorelbine and cisplatin and was stable 19 months later.¹³ Trabectedin and eribulin each appear in one published patient: progression on trabectedin,¹² control of bone metastases on eribulin.¹⁵

Pazopanib and anlotinib

These tablets block signals that tumours use to grow blood vessels.

Pazopanib, largest series: 12 patients, all metastatic and most in third line or later: 1 partial response, 4 with stable disease, 7 with progression; median 3.7 months without progression.¹
Pazopanib, an outlier: in a retrospective European (EORTC) analysis both of 2 intimal sarcoma patients responded. This was not reproduced in the larger series.¹⁴
Pazopanib, single patients: control for 16.3 months after most lesions had been irradiated;¹⁵ stable disease for about 22 months, stopped for fatigue;¹⁶ first-line treatment of an inoperable cardiac recurrence, with progression at 13 months.¹⁷ In one recent series both patients had to stop because of side effects.¹⁶
Anlotinib: in one MDM2-amplified cardiac recurrence the tumour shrank on anlotinib alone and treatment continued for more than 7 months before progression.¹⁸

We found no published outcomes in intimal sarcoma for sunitinib, regorafenib, sorafenib, cabozantinib or lenvatinib. Imatinib was started in 4 patients in Leuven; the abstract does not report how they did.¹⁰

CDK4/6 inhibitors

In intimal sarcoma there is no dedicated publication. Two patients are mentioned in passing in papers about other questions: one had stable disease on abemaciclib as second line and stopped after 4 months because of colitis;³ one with a CDK4-amplified recurrence received a CDK4/6 inhibitor in a trial and progressed within 2 months.¹⁶ In the laboratory, a cell line grown from one patient's recurrence was more sensitive to abemaciclib than to pazopanib.¹⁵

The clinical evidence comes from dedifferentiated liposarcoma, a different sarcoma that shares the MDM2/CDK4 amplification:

Palbociclib, phase 2, 60 patients: 57% were free of progression at 12 weeks; median 17.9 weeks without progression; one complete response.¹⁹
Abemaciclib, phase 3 (SARC041), 108 patients: median 9.7 months without progression against 1.5 months on placebo; 9% of tumours shrank. These results were presented at a congress in 2026 and had not appeared in a journal when we last checked.²⁰

In both studies the documented effect is delay of progression. Shrinkage was uncommon. Whether the result carries over to intimal sarcoma has not been tested.

MDM2 inhibitors

The only prospective trial ever run in intimal sarcoma tested milademetan at the National Cancer Center in Tokyo. Eleven patients with MDM2-amplified, TP53 wild-type tumours were enrolled and 10 were analysed. Two (20%) had responses lasting more than 15 months. The trial registry adds: disease control in 60%, median 4.7 months without progression, median survival 12.2 months. When the drug stopped working, the tumours had acquired TP53 mutations.²

In dedifferentiated liposarcoma both large trials of this drug class missed their main goal: milademetan against trabectedin (3.6 against 2.2 months without progression, not significant)²² and brigimadlin against doxorubicin (8.4 against 7.2 months, not significant).²¹ The milademetan trial is listed as terminated, and trade press reported in April 2025 that the manufacturer had ended development of brigimadlin.^{22, 35} No results in intimal sarcoma have been published for any MDM2 inhibitor other than milademetan.

Checkpoint inhibitors

For background, see our page on immunotherapy in MDM2-amplified sarcomas. Here is what has been reported in intimal sarcoma itself.

Report	Patients and tumour features	Result
Seoul National University⁴	2 patients with mismatch-repair-deficient ("MSI-H-like") tumours, pembrolizumab	One complete remission lasting 2 years, given at the third recurrence. One progression at 6.5 months
Case series³	3 patients, MDM2-positive, microsatellite stable, pembrolizumab (one combined with an undisclosed trial drug)	Tumours shrank in all three. Progression after about 6 months in one and after 12 months in another; the third was still responding after 8 cycles
Eight US centres⁵	24 cardiac sarcomas, 2 of them intimal	One of the 2 intimal sarcoma patients had durable benefit. Across the whole group, none of 11 patients on a PD-1 antibody alone responded
Single case²⁴	MSI-high, very high mutation count, PD-L1 above 90%, first-line pembrolizumab	Progression at 3 months despite three favourable markers
China-Japan Friendship Hospital, Beijing²³	3 patients given a PD-1 antibody after surgery or in combination with other drugs	One free of progression at 14 months, one alive more than 56 months after diagnosis, one died 11 months after surgery
Single patient in a laboratory study²⁵	Pembrolizumab for about 12 months	Complete response; recurrence 21 months after stopping, removed surgically and treated again
Single patient in a series of 28 sarcomas²⁶	Nivolumab alone, lung metastases	Stable for 6 cycles, progression after 6 more

About hyperprogression. The concern that tumours with MDM2 amplification may grow faster on checkpoint inhibitors comes from one study of 155 patients with various cancers. Six had MDM2-family amplification; all six failed treatment within 2 months and four met the criteria for hyperprogression. None of them had intimal sarcoma.²⁷ We found no published case of hyperprogression in intimal sarcoma, and the Beijing group reports none in its three patients.²³ That is not proof that it does not happen.

Surgery and radiotherapy for recurrence

All of the following are single patients, and patients fit for a second operation or focused radiotherapy are a selected group.

Repeat surgery: a recurrence at the suture line 31 months after the first operation was resected; the patient was alive 42 months after the first surgery.²⁸ One patient with metastases from the start had three operations for lung metastases and a resection of a local recurrence at 4 years, and lived 7 years.²⁹ In the Juntendo series one patient had two re-operations and died at 24 months.⁶
Radiotherapy to a local recurrence: repeat irradiation combined with pazopanib gave good local control, with survival of 50 months.³⁰ Radiotherapy for a focal recurrence 3 years after surgery of a coronary artery intimal sarcoma left no activity on PET 4 years later; the patient was alive at 7 years.³²
Focused radiotherapy to lung metastases: after removal of metastases and two courses of stereotactic radiotherapy, one patient was free of disease at 4 years without chemotherapy.³¹
Particle therapy: proton therapy for a recurrence in the aortic arch led to complete remission on PET/CT in a report from 2008.³³ Heavy-ion therapy for a recurrence at 18 months: alive at 22 months.⁶

People who lived for years after recurrence

They exist, and each is a single report. One patient had a metastasis removed from the thyroid 4.7 years and from the adrenal gland 6.3 years after diagnosis, and had no detectable disease at 12.5 years.³⁴ Another had lung metastases treated by radiofrequency ablation 7 years after surgery and was alive at 102 months with slow progression in the lung.¹¹ The Seoul patient described above had recurrences at 2 years 10 months and at 6.9 years before the remission on pembrolizumab.⁴ Others are listed in the section on surgery and radiotherapy.^{29, 30, 31, 32}

What has not been published

Any randomised or comparative study of treatment at recurrence.
A dedicated report of a CDK4/6 inhibitor in intimal sarcoma. For palbociclib and ribociclib there is not even a single described patient.
Results for any MDM2 inhibitor other than milademetan.
Survival after recurrence as a measured outcome.
More than one patient each for proton and heavy-ion therapy.
Systemic treatment of recurrent intimal sarcoma of the aorta, beyond isolated case reports.

Help fill the gap

What happens at recurrence is the least documented part of this disease. If you or someone in your family has been treated for a recurrence, what was done and how long it held is exactly the information that is missing. Tell us your course. No names are needed. With your explicit consent we add anonymised courses to this page.

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Frequently asked

Is there a standard treatment when intimal sarcoma comes back?

No. There is no randomised trial and no approved drug for this situation. The best documented drug treatment is anthracycline-based chemotherapy (38% response among 50 evaluable patients in the largest series). Where the recurrence is confined to one site, reports of long survival usually involve repeat surgery or radiotherapy. Decisions are made case by case, ideally at a sarcoma reference centre.

Which tumour tests come up in these reports?

Three. MDM2 and CDK4 amplification, because trials select on them. TP53 status, because the milademetan trial enrolled only tumours with intact TP53 and resistance came with acquired TP53 mutations. And mismatch-repair or MSI status, because the most durable responses to checkpoint inhibitors were seen in mismatch-repair-deficient tumours.

Do checkpoint inhibitors work in intimal sarcoma?

Sometimes. Durable responses have been published, most of them in tumours with mismatch-repair deficiency, which is a minority. In tumours without it the evidence is a handful of patients, and in a series of cardiac sarcomas none of 11 patients on a PD-1 antibody alone responded. No case of hyperprogression in intimal sarcoma has been published; the warning comes from six patients with other cancers.

This page is information, not medical advice. It summarises published reports and cannot know your situation. A treatment listed here is not a recommendation, and a treatment missing here is not ruled out. Please discuss everything with your own care team, ideally at a sarcoma reference centre.

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