Radiotherapy (RT) is one of the major cornerstones in managing gastrointestinal (GI) cancers. However, several side effects, such as intestinal inflammation, mucosal injury, and dysbiosis, often compromise this. The gut microbiota increasingly attracts much interest as an essential modulator of RT effects influencing immune responses and tissue repair. Through short-chain fatty acids such as butyrate, representatives of certain bacterial species play a crucial role under normal conditions, keeping the mucosal integrity intact and reducing oxidative stress-mediated damage. Dysbiosis, a state where diminished microbial diversity and increased pathogenic species in the microbiota are seen, amplifies RT-induced toxicity in patients. Clinical investigations highlight that microbiota-targeted interventions, including probiotics, prebiotics, and fecal microbiota transplantation, hold the means to augment RT efficacy and lessen toxicity. Increased microflora diversity and specific microbial profiles have yielded serious patient improvements. Advanced RT methods use stereotactic body radiotherapy combined with microbiota modulation as a promising technique to shield healthy tissue and maximize immune-mediated antitumor effects. Additionally, there is an implication in tumor behavior regulated by the intratumoral microbiota regarding the response to radiotherapy. Notably, the modulation of gut and tumor microbiota provides an avenue to optimize RT benefits in GI cancers, underscoring the importance of personalized therapy.

Stereotactic body radiotherapy (SBRT) delivers ablative radiation doses with sub-millimeter precision. Radiogenomic studies, meanwhile, provide insights into how tumor-intrinsic genetic factors influence responses to such high-dose treatments. This review explores the radiobiological mechanisms underpinning SBRT efficacy, emphasizing the roles of DNA damage response (DDR) pathways, tumor suppressor gene alterations, and inflammatory signaling in shaping tumor radiosensitivity or resistance. SBRT induces complex DNA double-strand breaks (DSBs) that robustly activate DDR signaling cascades, particularly via the ATM and ATR kinases. Tumors with proficient DNA repair capabilities often resist SBRT, whereas deficiencies in key repair genes can render them more susceptible to radiation-induced cytotoxicity. Mutations in tumor suppressor genes may impair p53-dependent apoptosis and disrupt cell cycle checkpoints, allowing malignant cells to evade radiation-induced cell death. Furthermore, SBRT provokes the release of pro-inflammatory cytokines and activates innate immune pathways, potentially leading to immunogenic cell death and reshaping the tumor microenvironment. Radiogenomic profiling has identified genomic alterations and molecular signatures associated with differential responses to SBRT and immune activation. These insights open avenues for precision radiotherapy approaches, including the use of genomic biomarkers for patient selection, the integration of SBRT with DDR inhibitors or immunotherapies, and the customization of treatment plans based on individual tumor genotypes and immune landscapes. Ultimately, these strategies aim to enhance SBRT efficacy and improve clinical outcomes through biologically tailored treatment. This review provides a comprehensive summary of current knowledge on the genetic determinants of response to stereotactic radiotherapy and discusses their implications for personalized cancer treatment.

Background: The development of immunotherapy checkpoint inhibitors (ICIs) has revolutionized cancer care. However, old patients are underrepresented in most clinical trials, although they represent a significant proportion of real-world patients. We aimed to evaluate the effectiveness and safety of ICIs in patients older than the age of 70. Methods: We performed a retrospective chart review of 145 patients aged 70 or older treated with ICIs for metastatic or unresectable cancer. Results: Median progression-free survival (PFS) was 10.4 months (95% CI 8.6–13.7), with no differences between octogenarians and septuagenarians (p = 0.41). Female gender (p = 0.04) and first-line treatment setting (p < 0.0001) were associated with a longer median PFS. Median overall survival (OS) was 20.7 months (95% CI 13.5–35.0 months), with no difference based on performance status, cancer site, gender, or between septuagenarians and octogenarians (all p > 0.005). Patients treated with ICIs in the first-line setting reported longer OS compared to treatment in the second-line setting (p < 0.001). Discontinuation of ICIs due to adverse effects was associated with both shorter PFS (p = 0.0005) and OS (p < 0.0001). Conclusion: The effectiveness of ICIs in older cancer patients primarily depends on the line of treatment and treatment discontinuation. Octogenarians experienced similar treatment responses, PFS, OS, and adverse effects compared to septuagenarians.