Retrospective Cohort Study of Caveolin-1 Expression as Prognostic Factor in Unresectable Locally Advanced or Metastatic Pancreatic Cancer Patients

Round 1

Reviewer 1 Report

The research article submitted by Bittoni et al showed that higher levels of Cav-1  expression were associated with a worse prognosis in patients with stage IV pancreatic cancer.  Overall, this is a timely paper for the field. The organization is of the context is clear and easy to follow. Therefore, it should be published given some minor issues stated in the following.

The following are a few comments/suggestions:

As the author appropriately point out, treatment of PDAC with Cav-1 specific inhibitors may improve advanced PDAC patient’s prognosis and has received much attention in the literature. Yet more discussion should be dedicated to how these inhibitors  can be translated into therapeutic application based on the outcomes of efficacy and toxicology, because translation of preclinical discovery into clinical outcome represents a great deal of interests of the readers.

Author Response

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Reviewer 2 Report

The authors present a retrospective cohort study of caveolin-1 expression as prognostic factor in un-resectable locally advanced or metastatic pancreatic cancer patients. The paper is very interesting since caveolin-1 may play a significant role in up-regulating pancreatic carcinoma and its nab-paclitaxel uptake. In may opinion the paper is acceptable in its present form .

Author Response

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Reviewer 3 Report

This study investigated (by immunohistochemistry) the expression of caveolin-1 (CAV-1) in a series of 39 patients with locally advanced or metastatic ductal adenocarcinoma of the pancreas (PDAC). Data were correlated with the first-line chemotherapy regimen (gemcitabine +/- nab-paclitaxel or FOLFIRINOX) and patient survival. The study results show that high-level CAV-1 expression was associated with worse patient outcome, and on multivariate analysis, CAV-1 was an independent predictor of prognosis. CAV-1 expression did not correlate with the type of first-line chemotherapy.

The study has a clear hypothesis, and the objective to investigate a possible link between CAV-1 expression and effect of first-line chemotherapy is both novel, clinically relevant, and based on sound scientific reasoning. The manuscript is well structured, and references are both relevant and up-to-date.

My concerns are the following:

- Study cohort: it is not entirely clear how many of the tissue samples stemmed from locally advanced or metastatic PDAC. In line 87, only metastastic PDAC is mentioned, whereas elsewhere it is stated that locally advanced PDAC was also included. In Table 1, the number of metastatic sites exceeds n = 39, indicating that for some patients, tissue samples from different metastatic sites were analysed. However, it is not clear how many patients had locally advanced PDAC only.

- Tissue samples:

1. Unfortunately, there is no information as to the type of specimens that were available for analysis. Did the tissues stem from core biopsies (eg. from liver metastases), from fine needle biopsies (FNB, eg. from the primary tumour), or from surgical resection specimens? This information is important, as the amount of tumour tissue varies between the different sample types. Especially in FNB-material, the amount of tumour tissue is often very limited. If this material was included in the study, how many tumour cells did these samples contain? Did the authors look at intratumour heterogeneity of CAV-1 immunostaining in slides from surgical tumour specimens to evaluate in how far limited biopsy material is representative?
2. In how many patients was tissue from both the primary tumour and the metastasis available?
3. Table 1 lists the results for lymph node metastases: were these regional or extraregional, and what was the sample type (FNA, surgical resection, ….)?

- Methods:

1. It is stated that the percentage of positive tumour cells was ennumerated, however, these data are not presented. Instead, three categories based only on the intensity of staining were used for further analysis. Why have the authors chosen not to use a combined immunohistochemical score (i.e., % of positive cells x staining intensity)?
2. Although CAV-1 is also expressed in the stroma of PDAC, and published evidence indicates that this is associated with aggressive tumour biology, the study evaluated CAV-1 expression in the cancer cells only. What was the reason for excluding stromal expression, and how can this have affected the study results?

- Results:

1. It is stated that the grade of tumour differentiation and the TNM stage were recorded, but as far as I can see, these data are not shared with the readers. Because this is basic information, and especially since CAV-1 expression has been shown previously to correlate with the grade of differentiation, these data should be included in the manuscript.
2. Figures 3 & 4: the survival data are plotted for the entire cohort. Because outcome differs between patients with locally advanced and metastatic disease, the authors may wish to comment on the results separate for both sub-cohorts.

- Minor comments:

1. There seems to be a contradiction in the text on lines 72-76. Could the authors have meant CAV-1 knock-down rather than expression?
2. Table 1: it is customary to display clinicopathologic data regarding the study cohort and study results in separate tables. Please, see also above (comment on study cohort and tissues/2).
3. Figure 2/b: the values “0” and “1” on the X-axis are not meaningful and should be replaced by primary tumour and metastasis.
4. The manuscript would benefit from English editing (eg. “germinal BRCA2 variant” instead of “germ line”).

Author Response

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Round 2

Reviewer 3 Report

The authors have adequately addressed most of the questions and comments.