Intratumoral injection therapies for locally advanced pancreatic cancer: systematic review

Intratumoral injection therapies have been studied as novel (complementary) treatment options for improved local tumour control of locally advanced pancreatic cancer. A literature search was conducted in PubMed, Embase, and the Cochrane Library, including 52 studies treating 1843 patients with 5 different modalities of intratumoral injection therapies. There was a large variation in safety and survival; however, most intratumoral injection therapies seem safe, although current data are insufficient for firm conclusions regarding the added value to survival. Introduction Pancreatic cancer has one of the worst prognoses of all cancers. Patients with locally advanced pancreatic cancer have a 12.7-20.2 per cent chance of receiving curative surgery after induction systemic chemotherapy. Intratumoral injection therapies have been studied as complementary treatment options for improved local tumour control. The aim of this systematic review was to provide an overview of intratumoral injection therapies, their safety, and oncological outcome in patients with locally advanced pancreatic cancer. Methods A literature search was conducted in PubMed, Embase and the Cochrane Library for articles written in English up to 28 November 2022. All study designs involving at least five patients with locally advanced pancreatic cancer who were treated with an intratumoral injection therapy were included. Critical appraisal of the included studies was performed using the Newcastle-Ottawa scale. Results After evaluation of the 1680 articles yielded by the systematic search, 52 studies treating 1843 patients were included. Included intratumoral injection treatment modalities comprised iodine-125 (I-125) seed brachytherapy (32 studies, 1283 patients), phosphorus-32 (P-32) microbrachytherapy (5 studies, 133 patients), palladium-103 (Pd-103) seed brachytherapy (2 studies, 26 patients), immunotherapy (9 studies, 330 patients), and chemotherapy (4 studies, 71 patients). Overall survival ranged between 7.0 and 16.0 months for I-125, 5.2 and 15.5 months for P-32, 6.9 and 10.0 months for Pd-103, 5.8 and 13.8 months for immunotherapy, and 9.0 and 16.2 months for chemotherapy. Severe complication (greater than or equal to grade III complications using Clavien-Dindo classification) rates were 6.2 per cent for I-125, 49.2 per cent for P-32, 15 per cent for Pd-103, 57.9 per cent for immunotherapy, and 0 per cent for chemotherapy. Conclusion Five intratumoral injection therapies are described and an overview is reported. Some intratumoral injection therapies for patients with locally advanced pancreatic cancer seem safe, although P-32 microbrachytherapy and immunotherapy require additional evidence. Currently available data are insufficient to provide firm conclusions regarding the added value to survival. The potential advantage of intratumoral injection therapies complementary to conventional care should be studied in well designed RCTs.