The INDEPSO-ISPSM Consensus on Peritoneal Malignancies-Methodology.

: The numerous international guidelines on cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) do not cover many clinically relevant issues for which evidence is limited and some regional issues (HIPEC in limited resource settings, age-limit for CRS, etc.). We describe the methodology of a consensus CRS and HIPEC for peritoneal malignancies carried out under the aegis of the two national societies for peritoneal oncology-INDEPSO and ISPSM. The modified Delphi technique was used with two rounds of voting. Eight key topics were selected by a working group of 29 members. Questionnaires comprising of closed-ended questions were disseminated through the online SurveyMonkey (http://www.surveymonkey.com) platform. A panel of 56 surgical, gastrointestinal, and gynecologic oncologists with a minimum of 5 years of experience with CRS-HIPEC voted on 260 questions. A consensus was reached if any of the options received 70% or more votes (> 90% = strong consensus). The response rate was 98.2% in round I and 94.6% in round II. A consensus was achieved on 80.7% questions after two rounds (43.0% after round I; 36.9% after round II). It was the highest in the enhanced recovery after surgery (ERAS) section (93.3%) and the lowest (68.0%) for ovarian cancer. A strong consensus was reached on 59 (22.6%) questions (highest for  the technical section (34.2%); lowest in the ERAS section (16.6%)). This consensus which had a high rate of participation should be a useful clinical resource for surgeons treating peritoneal malignancies in India and other regions with a similar demographic and socioeconomic background. The online version contains supplementary material available at 10.1007/s13193-024-02118-2.