Surgery for Liver Metastases From PDAC

Dissemination from pancreatic ductal adenocarcinoma (PDAC) occurs in clinical practice either in the form of recurrence after initial treatment with curative intent or more frequently is manifested already at the time of diagnosis. Traditionally corresponding disease states are considered not to be eligible for meaningful aggressive therapies to be implemented. Instead, palliative therapies are instituted with a very limited survival. However, with the development of local as well as more effective systemic therapeutic regimens, a variety of clinical situations must be reevaluated.

In PDAC, disseminated to the liver, the traditional view as that the corresponding lesions are non-treatable by aggressive chemotherapy followed by surgical interventions and generally, surgery has been considered obsolete in this patient cohort5. Despite these early discouraging results there are some reports, from selected cohorts, indicating more promising survival rates after resection of metastasis(es) than ever earlier described6. Moreover, during recent years there has been significant improvement in the efficacy of chemotherapy regimens available for patients with localized as well as disseminated PDAC that may enhance the effect of surgical removal of macroscopic tumor manifestations.

The same may be true for alternative limited manifestations of metastatic PDAC disease. Hence an unbiased approach must be explored to the updated management opportunities in terms of assessing the incidence, safety, feasibility, tolerability and possible disease control options.

According to the Swedish and Danish pancreatic cancer registry the overall median survival (OS) of patients with pancreatic cancer is about 6-7 months while studies demonstrate 9-15 months median survival when palliative chemotherapy is used7, 8.

Hitherto, no prospective, population-based study, with intention to treat design, has been presented to define the role of aggressive oncological regimens with successive macroscopic eradication of tumor lesions as exemplified by surgery in disseminated PDAC. The evidence at hand comes from retrospectively collected and selected cohorts where comparison is often made to surgical palliation alone (intestinal bypass surgery) or best supportive care. The reported median survival after surgery varies widely from 7.6 months to as long as 56 months9. A recent case matched study suggested that in selected cases, surgery may improve median survival from about 1 to 2 years10. Corresponding data just reflect the large impact of selection on either the intervention and/or the control group. The main drawback of the available literature is the general lack of population based, intention to treat data and lack of clear definition of disease stages that severely limit the usefulness of these results in clinical decision making.

The evidence for applying invasive treatment for extrahepatic dissemination of PDAC is even more limited although dissemination to the lungs may be associated with somewhat longer overall survival than other locations 11.

Despite increasing evidence for some role of updated multimodal treatment options in disseminated PDAC there is a strong need for an intention to treat designed prospective, population-based study to investigate the value of corresponding regimens in PDAC.

Eligible for enrolment are all patients presenting with the following characteristics:

Primary cohort; Synchronous or metachronous liver metastasis(es) from PDAC without signs of extra hepatic disease. This cohort is subdivided:

• Limited liver disease: Synchronous or metachronous uni- or bilobar liver metastasis(es) from PDAC. The number of metastases shall be < 4 and the largest < 5 cm (2 cm if ablative treatment is planned) and no signs of extrahepatic dissemination. This cohort forms the basis for sample size calculation and primary outcome.
• Extended liver disease: Liver limited metastasis that do not fit into the limited liver disease cohort but are still evaluated at a multidisciplinary conference and judged as amendable for treatment with curative intent Secondary cohort; PDAC patients with limited (unilocular) dissemination to intra- or extra-abdominal locations rendering the lesion(s) amenable to either; SBRT, alternative external radiation options, surgery, thermal ablation or a combination of these. Patients with loco-regional recurrences of PDCA as defined as those detected in the remaining part of the resected organs (e.g. the gastric or pancreatic remnant), in the anastomotic area, the anatomic area representing the original resection bed, regional remaining lymph nodes. Patients with isolated loco-regional recurrences as defined as those emerging and detected in the above-mentioned sites, and with no signs of distant metastases.

All these patients are identified at multidisciplinary tumor boards in each participating center.

Patients deemed fit for oncological treatment are enrolled and chemotherapy started. After at least 2 months of chemotherapy patient status is reevaluated with CT scan/MRI and PET-CT and in case of response (stable disease or regression according to the RECIST 1.1 criteria) and also evaluating tumour markers (CA19.9), local treatment is given.

For inclusion in the Primary "Limited liver disease" cohort" a minimum of 4 months chemotherapy treatment is given.

If response is not achieved on initial oncological treatment, further treatment may be given and disease status re-evaluated every other month as long as considered clinically relevant-meaningful. Patients that do not achieve stable disease/regression will continue palliative treatment as clinically indicated.