In this study, the combination of staging laparoscopy with PIPAC was equally safe and well tolerated as staging laparoscopy alone. Surgery time was longer in the LP group, but early clinical outcomes and hospital length of stay were similar. The potential benefits of added PIPAC remain yet to be investigated.
PM comprises a heterogeneous group of quite different primaries. Most frequent origins spreading within the abdominal cavity at initial presentation are ovarian (46%), oesogastric (14%), and colorectal tumors (5%) (1, 2, 4). Staging laparoscopy for primary digestive malignancies allows identification of occult peritoneal disease (19, 20). According to ESMO guidelines, staging laparoscopy is recommended for all patients with locally advanced gastro oesophageal adenocarcinoma (>cT3 and/or cN+ stage) (12). In particular, tumors that develop within the abdominal cavity (Siewert II and III) are more susceptible to present a peritoneal metastatic spread (6%-17%) upon initial diagnosis (21, 22). Hence, diagnostic laparoscopy is an integral part of locally advanced gastric and gastroesophageal junction cancer staging (21). Occult PC precluding upfront curative surgery is discovered in 15 to 40% of patients with locally advanced gastric cancer during staging laparoscopy (23–25). ESMO guidelines recommend a staging laparoscopy in all potentially resectable stage IB–III gastric tumors, (12) whereas the SAGES guidelines recommend staging laparoscopy for T3/T4 gastric cancer without evidence of lymph node or distant metastasis on high quality preoperative imaging (20). In colorectal cancer, approximately 20–30% of patients with pT4 or perforated tumors develop metachronous peritoneal metastases, but staging laparoscopy is not performed systematically (26, 27). In this situation, primary tumor resection is often necessary even in presence of PM to treat or even to prevent imminent obstruction, perforation or bleeding (20); as such, the additional value of staging laparoscopy in the primary and metastatic colorectal cancer has not yet been clearly defined (28, 29). However, 10% of occult peritoneal metastases for pT4 cancer are diagnosed during a planned second look laparoscopy 6 months after resection, even when no metastases are detected on high-resolution abdominal imaging (26). For appendiceal tumors, the detection rate of PM is up to 23% at one year after primary resection for mucinous neoplasm. Thus, laparoscopy was suggested as a primary screening tool during postoperative follow-up, to identify occult metastases undetectable on CT scan (30). In the context of ovarian epithelial cancer, staging laparoscopy was suggested as a routine in the initial diagnostic workup (31), leading to upstaging of the disease through detection of PM in 22.6% of patients (32).
Prognosis of patients with advanced PM is dismal and depends mainly on disease extent and response to therapy (7). Resistance to systemic chemotherapy due to limited drug distribution in the peritoneum and limitations in early-stage disease diagnosis with non-invasive imaging make PM management particularly challenging (3).
Complete abdominal surgical exploration in high-risk patients with PM has been described and evaluated in prospective non-randomised studies (33–37). Similarly, a systematic second look is proposed for early diagnosis of peritoneal metastases from colorectal origin, not visible on imaging. This second-look allows early treatment of patients with low PCI; although this may improve survival in selected cases, it rarely allows a curative treatment strategy. To overcome this problem intraabdominal chemotherapy was evaluated as adjuvant treatment in cohort studies (38–40). These preliminary studies reported promising results of adjuvant HIPEC for high-risk colon cancer, decreasing the incidence of peritoneal metastasis to 0–4% after IntraPeritoneal treatment. Five randomized studies aimed to determine the efficacy of adjuvant HIPEC in patients with locally advanced colon cancer: PROPHYLOCHIP–PRODIGE 15 trial (41), COLOPEc trial (27), APEC Study (42), HIPECT4 trial (43) and PROMENADE trial (44). Systematic second-look surgery plus oxaliplatin-HIPEC did not improve disease-free survival compared to standard surveillance in ROPHYLOCHIP–PRODIGE 15 and COLOPEc, but was related to up to 41% of postoperative complications (grade 3–4) (27, 41). HIPECT4 trial observed a reduced risk of peritoneal recurrence from 36–18% at 36 months for T4 colon-rectal carcinoma after adjuvant HIPEC (43). Results of APEC and PROMENADE trials are still awaited (42, 44).
Pressurised intraperitoneal aerosol chemotherapy (PIPAC) has been proposed as an alternative mode for intraperitoneal drug delivery in certain situations, claiming improved distribution, enhanced tissue uptake, better tolerance, and repeatability using minimally invasive access (5, 6, 8). Favourable initial reports (7) have triggered the adoption of PIPAC as a drug delivery technique. PIPAC has been proposed as an alternative method of intraperitoneal drug delivery, claiming improved distribution, enhanced tissue uptake, better tolerance and repeatability using minimally invasive access (5, 6, 8). In recent systemic reviews, PIPAC is considered a safe and promising treatment alternative for patients with advanced isolated refractory peritoneal disease (7, 8).
Adjuvant PIPAC for high-risk patients is an intriguing concept which entails a risk of overtreatment. Added PIPAC in this study did not increase the risk or tolerance of staging laparosocopy alone. On the other hand, the risk of missed opportunities (no PIPAC with patients with positive cytology) is to consider and might favour local spread. Three prospective randomized trials are currently recruiting to assess PIPAC as adjuvant treatment: the GASPACCO (45) and PIPAC-OPC4 (46) trials for T3-4 Gastric Cancer and the PIPAC-OPC3 CC trial for high risk colon cancer (47).
Following the principles of the IDEAL framework allowing standardized approach, future prospective studies are needed to confirm the efficacy and oncologic benefits of PIPAC (48). Furthermore, a registry for quality control supported by the International Society for the Study of Pleura and Peritoneum (ISSPP) was launched in 2020. This international database hosted at the University of Odense will facilitate future research with prospective monitoring (49).
The current study has some limitations which are mainly related to its retrospective nature and limited patient number. Small differences between the comparative groups might have passed undetected due to type II error. Finally, although baseline characteristics of patients were comparable there was no random allocation for the two groups with a consequent risk for selection bias.