The Pathologic Peritoneal Cancer Index (PCI) Strongly Differs From the Surgical PCI in Peritoneal Metastases Arising From Various Primary Tumors

Our plain-English summary of The Pathologic Peritoneal Cancer Index (PCI) Strongly Differs From the Surgical PCI in Peritoneal Metastases Arising From Various Primary Tumors, by A. Bhatt, Y. Yonemura, S. Mehta, et al (Annals of Surgical Oncology, 2020).

The study

• Authors: A. Bhatt, Y. Yonemura, S. Mehta, N. Benzerdjeb, P. Kammar, L. Parikh, A. Prabhu, S. Mishra, M. Shah, S. Shaikh, V. Kepenekian, I. Bonnefoy, M.D. Patel, S. Isaac, O. Glehen
• Journal: Annals of Surgical Oncology
• Published: 2020;27(8):2985-2996
• Cited by: 58 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Background: The surgical peritoneal cancer index (sPCI) is calculated based on a subjective evaluation of the extent of peritoneal disease during surgery. The pathologic PCI (pPCI) may be a more accurate and objective method for determining the PCI. This study aimed to compare the sPCI and pPCI and to study the potential pitfalls and clinical implications of using the pPCI.

Methods: This prospective study (July to December 2018) included all patients undergoing cytoreductive surgery (CRS). The pPCI was calculated for each patient and compared with the sPCI. The impact of potential confounding factors on the difference between pPCI and sPCI was evaluated.

Results: Among 191 patients undergoing CRS at four centers, the pPCI and sPCI were concordant for 37 patients (19.3%). The pPCI was lower than the sPCI for 125 patients (65.4%) and higher for 29 patients (15.1%). The concordance between the two groups was maximum for gastric cancer (38.8%) and colorectal cancer (27.6%) and least for mesothelioma (6.7%) and rare primary tumors (5.6%) (p = 0.04). The difference was 0 to 3 points for 119 patients (62.3%), 4 to 5 points for 27 patients (14.1%), and more than 5 points for 45 patients (23.5%). The rate of concordance was not influenced by the use of neoadjuvant chemotherapy (NACT) (p = 0.4), but the difference was greater when NACT was used (p = 0.03).

Conclusions: The pPCI strongly differs from the sPCI for patients undergoing CRS for peritoneal disease and may provide a more accurate evaluation of the peritoneal disease extent. Further studies are needed to determine its prognostic value compared with sPCI, and consensus guidelines are needed for calculating it.

In plain English

This prospective study at four centers in France, Japan and India included 191 patients operated on from July to December 2018: 182 had cytoreductive surgery, 3 had adjuvant heated abdominal chemotherapy (HIPEC), and 6 had second-look surgery. Prophylactic HIPEC and second-look patients were included even if pathology found no disease. Fifteen had peritoneal mesothelioma; others had appendix, colorectal, ovarian, stomach or rare cancers. Asbestos was not studied. The authors compared the surgeon's score of disease spread in the abdominal lining made during surgery (surgical peritoneal cancer index, sPCI) with a score from the pathologist's examination of removed tissue (pathologic PCI, pPCI). Scores matched for 37 patients (19.3%); the pathologic score was lower for 125 (65.4%), higher for 29 (15.1%). Matching was most common in stomach cancer (38.8%) and least in mesothelioma (6.7%) and rare tumors (5.6%). In 39 patients (20.4%), microscopy found disease in areas the surgeon had scored normal. The authors concluded the pathologic score strongly differs from the surgical one and may be more accurate. Survival was not studied, and their pathology protocol has not been validated.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Prospective study at four centers comparing the surgeon's intraoperative peritoneal cancer index with a pathology-based index in the same patients
• Who was studied: 191 patients treated surgically at four centers (Lyon, France; Osaka, Japan; Ahmedabad and Mumbai, India), 1 July to 31 December 2018. By procedure: 182 cytoreductive surgery, 3 adjuvant HIPEC for gastric cancer, 6 second-look procedures. Patients having prophylactic HIPEC or second-look surgery were included even if histopathology showed no disease. By primary site: appendix 49, colorectal 47, ovary 44, stomach 18, mesothelioma 15, rare primary tumors 18. The article describes the 15 mesothelioma patients as having peritoneal mesothelioma.
• Exposure: No asbestos or fiber exposure was studied. The comparison was between the surgical peritoneal cancer index (sPCI), estimated by the surgeon during the operation, and the pathologic PCI (pPCI), scored from microscopic examination of the removed tissue.
• Main results:
  • Among all 191 patients, the two scores were the same for 37 patients (19.3%). The pathologic score was lower than the surgical score for 125 patients (65.4%) and higher for 29 patients (15.1%).
  • The share of patients whose scores matched varied by primary tumor site (p = 0.04): gastric cancer 38.8%, colorectal 27.6%, appendiceal 18.3%, ovarian 13.6%, mesothelioma 6.7%, rare primary tumors 5.6%.
  • Among all patients, 39 (20.4%) had disease on microscopy in peritoneal areas the surgeon had scored 0.
  • The difference between the two scores was 0 to 3 points for 119 patients (62.3%), 4 to 5 points for 27 patients (14.1%), and more than 5 points for 45 patients (23.5%).
  • Whether the scores matched was not influenced by neoadjuvant chemotherapy (p = 0.4). The size of the difference was greater when neoadjuvant chemotherapy was used (p = 0.03).
• The authors' conclusion: The authors concluded that the pathologic PCI strongly differs from the surgical PCI and may provide a more accurate assessment of peritoneal cancer extent. They called for further studies of its prognostic value and for consensus guidelines on calculating it.
• Limitations the authors state:
  • Fixing specimens in formalin shrinks them, reducing measured tumor size.
  • For patients with incomplete cytoreduction, not all regions could be evaluated by pathology.
  • The effect of chemotherapy response score or grade could not be studied because the centers used different scoring systems.
  • Patient populations and treatment protocols differed between centers.
  • Follow-up was short, so the effect of the pathologic PCI on survival was not studied.
  • The pathologic evaluation protocol has not been validated.

Topics

Medical terms in this study, explained in our Lexicon: Peritoneal Cancer Index (PCI), Cytoreductive Surgery, Confounding, Stomach Cancer, Colorectal Cancer, Mesothelioma, Neoadjuvant Chemotherapy.

Related studies

• Target region resection in patients undergoing cytoreductive surgery for peritoneal metastases-is it necessary in absence of visible disease? — A. Bhatt, Y. Yonemura, et al. (2020)
• From the archives of the AFIP: primary peritoneal tumors: imaging features with pathologic correlation — A.D. Levy, J. Arnáiz, et al. (2008)
• Cytoreductive Surgery and Hyperthermic Intraperitoneal Chemoperfusion in Adolescent and Young Adults with Peritoneal Metastases — M. Dhir, L. Ramalingam, et al. (2017)
• Current Management and Future Opportunities for Peritoneal Metastases: Peritoneal Mesothelioma — H.R. Alexander, C.Y. Li, et al. (2018)
• A proposal of Brazilian Society of Surgical Oncology (BSSO/SBCO) for standardizing cytoreductive surgery (CRS) plus hyperthermic intraperitoneal chemotherapy (HIPEC) procedures in Brazil: pseudomixoma peritonei, appendiceal tumors and malignant peritoneal mesothelioma — T.P. Batista, B.J.Q. Sarmento, et al. (2017)
• Lymph node metastases in diffuse malignant peritoneal mesothelioma — D. Baratti, S. Kusamura, et al. (2010)

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