Proton pump inhibitors (PPIs) are the most commonly used anti-acid drugs worldwide, including among cancer patients. However, drug-drug interactions between PPIs and other agents may lead to decreased drug absorption with possible reduced therapeutic benefit, or even increased toxicity. Unfortunately, only scarce data exist regarding the safety of concomitant PPI use with anti-cancer agents. We aim at reviewing current evidence on this possible interaction by dividing anti-cancer agents by class. Until further data is available, we encourage healthcare providers to limit unnecessary PPI overuse.

Antibiotics, cancer risk and oncologic treatment efficacy: a practical review of the literature Moises S Martins Lopes1, Larissa M Machado1, Pedro

The first confirmed case of coronavirus disease 2019 (COVID-19) in Brazil and Latin America was reported on February 26, 2020, in São Paulo. The outbreak of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) has placed unprecedented strain on health-care services worldwide. Asymptomatic health-care workers (HCW) are a potential source of SARS-CoV-2 transmission, especially to immunocompromised Oncology patients. Screening of these HCWs may help contain transmission and isolate only those who require it. At Centro de Terapia Oncológica (CTO), an Oncology clinic in Petrópolis, RJ —Brazil, all HCWs were screened for SARS-CoV-2 in order to isolate those who were asymptomatic/symptomatic and positive for the virus. They were all tested through IgM/IgG rapid testing and those who had symptoms were also tested with nasopharyngeal swabs for reverse transcription polymerase chain reaction (RT-PCR) tests besides IgM/IgG reactivity. Amongst the 60 tested employees, 4 were positive for SARS-CoV-2 and were isolated. This method may be useful for health-care services to detect asymptomatic HCW and maintain workers’ and patients’ health, as transmission probability could be reduced while avoiding becoming short-staffed during this time of crisis.

Background: Peritoneal carcinomatosis is usually a terminal disease with short median survival in patients with gastric cancer. Systemic FOLFOX is one of the most used regimens in the first-line treatment of metastatic gastric cancer. However, there is scarce evidence that cytoreductive surgery (CRS) and intraperitoneal heated chemotherapy (HIPEC) improves oncological outcomes of patients with advanced gastric cancer. Methods: Herein we present a case of a young woman with advanced gastric cancer with omental and peritoneal metastases who achieved an excellent response after 6 months of FOLFOX followed by CRS and HIPEC. Results: A 53-year-old woman was diagnosed with advanced gastric carcinoma, with extensive omental caking and several peritoneal implants measuring 2 cm at the largest diameter. The patient received mFOLFOX6 for 6 months with excellent clinical and radiographic response. She was then submitted to a D2 total gastrectomy followed by CRS and HIPEC with mitomycin. The final pathology report showed a focal adenocarcinoma in the stomach measuring 0.4 mm with no residual tumor in the peritoneum (ypT1ypN0). The patient has been well and disease free for more than 4 years. Conclusion: While still controversial, CRS followed by HIPEC may be a curative therapeutic option for highly selected patients.

E23575 Background: STS include a heterogeneous group of malignancies that arises from or into connective tissues and limbs are the preferential primary sites. An adequate local control with multimodality therapy can be obtained in most cases. An additional approach, that is, the IORT-LK is able to deliver high dose to risky areas for recurrence, minimizing the toxicity to structures around the target. Such an importance is even greater in abdominal sarcomas, because there is some difficulty in removing the whole neoplasia with clear margins. IORT-LK has the advantage of higher Relative Biological Effectiveness (RBE), a mathematical model that measures the potential for tumour double-strand break (radiation effectiveness), that is close to Proton beam and higher than electron beam. Nevertheless, IORT-LK is not free of complications. It has been reported peripheral neuropathy and enteritis, in cases of limb and abdominal STS, respectively. Methods: In this retrospective study from a single Brazilian institution (Hospital Alemão Oswaldo Cruz), we reported 6 patients with histologically confirmed STS, that underwent IORT-LK (Intrabeam - Carl Zeiss). There are 3 male and 3 female patients, with a median age 48 years, and mean of 39 years. The histological subtypes are as follows: fibromyxoid sarcoma, high grade pleomorphic sarcoma, desmoid tumor, chondrosarcoma, dedifferentiated liposarcoma and malignant schwannoma - one subtype for each patient. The primary sites are: inferior limb (3), superior limb (1) and abdomen (2). Results: IORT-LK was administered in doses that ranged from 14 to 15 Gy to the involved area. Two patients, each one with a limb STS, received also neoadjuvant chemotherapy. With a mean follow-up of 30 months, there is no local recurrence among the 6 patients reported. The first patient received the IORT-LK in April, 2017 and the last one in July, 2019. All of them had clinical observation up-to-dated on January, 2020. No serious complications were observed, but one patient had a moderate local infection. Conclusions: The therapy was well tolerated. We must emphasize that dose previously used by Brussiers was slightly superior than ours but with electrons and not Low-Kylovoltage. In his pilot study it was used 17 Gy for treatment of abdominal sarcomas. In sum, we believe that IORT-LK has higher RBE than previous available equipment and can improve local control of STS, mainly those that arise on the extremities. Future studies must be carried out to confirm our initial impression.