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Introduction Peritoneal metastasis secondary to gastric cancer is associated with poor prognosis. Recent studies have shown that cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) may be an efficacious treatment option for an otherwise palliative condition. Methods A retrospective single institutional study of patents diagnosed with gastric carcinoma and peritoneal metastasis and treated with CRS and HIPEC from February 2015 to December 2019. Results Sixteen patients with gastric cancer and peritoneal carcinomatosis were treated with CRS and HIPEC. Three patients underwent upfront surgery, and five patients underwent interval surgery. The mean peritoneal cancer index (PCI) was 3.5, and adequate complete cytoreduction (CC) score of 0/1 was achieved in all patients. All patients received HIPEC with mitomycin C. Major surgical complications were in 12.5% of patients. Grade I surgical site infection was present in one patient. Three patients had prolonged gastrointestinal (GI) recovery. The 30-day mortality was zero. Median follow-up time was 39 months. The median progression-free survival (PFS) was 12 months (95% confidence interval [CI] 6.86–17.13). The median overall survival (OS) was 17 months (95% CI 6.36–27.64). Conclusion Multidisciplinary treatment of perioperative chemotherapy with CRS and HIPEC is a promising treatment option, which may prolong survival in selected patients, and large randomized clinical trials are warranted for it to become standard of care.

633 Background: Peritonectomy is the important components in management of peritoneal surface malignancies (PSM). Immunofluoresecne study done after involved field peritonectomy (IFP) has showed diease in areas not suspected on gross examination stressing the need for total parietal peritonectomy (TPP) for complete cytoreduction. The aim of this study was to assess the morbidity & mortality, recurrence pattern & oncological outcomes of extent of parietal peritonectomy with CRS & HIPEC for colorectal carcinoma. Methods: Patients with PSM from CRC underwent TPP or IFP with CRS- HIPEC. Pre & intraoperative data were analyzed with main focus on postoperative morbidity, mortality, recurrence pattern and oncological outcomes. Results: 40 cases of CRC of which four upfront, 17 interval and 19 recurrent cases. 19 & 21 patients underwent TPP & IFP respectively. Base line characteristics were comparable except median PCI (17 versus 12). TPP group had longer duration of surgery (11 vs 9), more blood loss (1300 vs 700 ml) increased diaphragmatic resections ( 46.2% vs 14.2%), multivisceral resection ( 46.2% vs 28.5%). Number of bowel resections, anastomosis and stoma were comparable. Overall TPP group had more G3-G5 morbidity (46.1% vs 35.7%) & surgical morbidity (30.7% vs 21.5%) . TPP group had increased pleural & intra-abdominal collections which needed intervention. With a median follow up of 30 months, DFS was significantly higher in TPP group (12months vs 8months, p < 0.01) and median overall survival was 21 months in IFP group (yet to be achieved in TPP group). TPP group had most of the recurrences in visceral liver & lung (50.0%) followed by peritoneal (37.5%) & nodal (12.5%) whereas in IFP it was peritoneum (42.8%), visceral ( 38.4%) & nodal (15.3%). Conclusions: It is the first prospective comparative study done on total parietal peritonectomy in PSM of colorectal cancer origin. TPP group had significantly higher DFS, with comparable postoperative morbidity. However, longer follow up and a prospective multi-institutional randomized study needs to be designed for more evidence of the same.

631 Background: Early tumor shrinkage (ETS) and depth of response (DoR) predict overall survival (OS) in first-line chemotherapy + anti-EGFR monoclonal antibodies in KRAS wild-type metastatic colorectal cancer (mCRC). This association and the predictive accuracy of response measurements were investigated in the first-line setting for FOLFOX/FOLFIRI plus cetuximab. Methods: We performed a study of FOLFOX/FOLFIRI plus cetuximab as first-line treatment in Indian patients with KRAS wild-type mCRC. The primary endpoint was response rate (RR), and secondary endpoints included progression-free survival (PFS), overall survival (OS), and safety. Radiologic assessments at week 8 were used to calculate the relative change in the sum of the longest diameters of the target lesions. Cox regression models analysis investigated associations between ETS and overall survival (OS) and progression-free survival (PFS). Results: Sixty (78.9 %) of 76 patients had ETS, which was associated with prolonged PFS and OS. Both ETS and DoR were able to predict survival as accurately as RECIST response. Both ETS and DoR were associated with PFS and OS at the univariate analyses and in the multivariate models stratified for other prognostic variables. In the study patients, the RR, median PFS, and OS were 68.4 %, 13.1 months, and 30.6 months, respectively. Median DpR was 52%. The DpR correlated with OS as well as PFS. FOLFOX plus cetuximab was active as a first-line, with no major toxicities. Conclusions: Our prospective evaluation of chronological tumor shrinkage showed that ETS and DpR correlate with outcomes in patients with KRAS wild-type mCRC who receive cetuximab-based chemotherapy. Achieving rapid and deep tumor shrinkage consistently delays tumor progression and prolongs survival in patients treated with first-line chemotherapy plus cetuximab. ETS is a promising and valuable end point for clinical trials’ design deserving further investigation.

661 Background: Robotic surgical systems have dramatically changed minimally invasive surgery as they could potentially address limitations of laparoscopic rectal surgery. This prospective observational study is conducted to evaluate the safety, technique, and outcomes (operative, postoperative,functional and oncological long term) of robotic-assisted rectal surgery for carcinoma rectum in the Indian set up. Methods: This was a prospective observational study conducted between 2010 and 2018, including 135 patients, diagnosed of rectal carcinoma. Patients underwent robotic rectal cancer surgery in form of either low anterior resection (LAR) or abdominoperineal resection (APR). Intraoperative, postoperative data were analysed. Results: Out of 135 patients, 67.5% were male, aged between 34-80 years, 85% had ECOG 0. All patients had adenocarcinoma rectum, with 15% mid rectum and 55% in lower rectum. 85% had stage III disease. 77.5% had received neoadjuvant chemoradiation. 82.5% had LAR and 17.5% APR. Average operative time including docking time and surgery time was 226.32 min (170-300 min), mean blood loss was 146.76 ml (120-200 ml), there were 3 conversion to open surgery. Bowel sounds appeared on average on 3rd day. All margins were negative in all patients, mesorectal grade was complete in 95% and near complete in 5%. Mean number of lymph nodes harvested is 9.5 (2-32). Complete pathological response rate was 39%. 2 patients had anastomotic dehiscence after 1 month. Minor complications were noticed in 10% patients. All had acceptable quality of life and well retained bladder function, with 18% sexual dysfunction. Five year DFS was 85% and OS was 94%. Local recurrence was 2.1%. Conclusions: This is one of the largest single center Indian data available. In conclusion, robotic rectal surgery has several benefits in the treatment and should be part of the armamentarium of the experienced surgeon dealing with rectal cancer. We conclude that the robotic-assisted rectal cancer surgery is safe and an oncologically feasible technique with well retained functional outcomes and has lived up to its hope.