**8. Post-radiation toxicity and complications**

In the scientific literature, the terms "acute toxicity" and "late toxicity" are defined in a variety of ways. In certain contexts, the term "acute toxicity" refers to the development of unfavorable consequences that take place both during the course of treatment and up to 42, 60, or 90 days following the completion of radiation therapy. Late toxicity is when an impact does not show up for 90 days or even years after it has been exposed to something. Although complications are reported to be slightly higher (10–15%) in patients with the locally progressed disease, the incidence of late sequelae in individuals with early-stage cervical cancer treated with RT is approximately 3.5%. However, complications are reported to be slightly higher in patients with more advanced diseases. The logic for this variance is straightforward: as the clinical stage of a patient continues to advance, the total dosage to central structures has a tendency to increase (e.g., 85–90 Gy are administered to the cervix in clinical stage III and IV patients). We can conclude that the risk of problems is related to the clinical stage, the volume of tissue being treated, the patient's anatomy, and the total dosage supplied to certain tissues [37].

Mild tiredness and mild to moderate diarrhea are common side effects of pelvic radiation but may be managed with antidiarrheal drugs. Some patients may also have mild bladder discomfort, which can be a sign of a urinary tract infection. Patients receiving treatment with extended fields may experience nausea, stomach discomfort, and a reduction in peripheral blood cell counts. Concurrent chemotherapy considerably increases the risk of hematologic and gastrointestinal problems. The most prevalent sexual problems after irradiation are ovarian insufficiency in premenopausal women and vaginal stenosis in vaginal radiation patients. Vaginal stenosis is a tightening or narrowing of the vaginal canal that can interfere with a physical exam or sexual function. Its prevalence ranges from 20 to 88% [38]. Ovarian failure occurs in all premenopausal individuals treated with pelvic radiation unless the ovaries have been transferred. Uterine perforation, fever, and the common complications associated with anesthesia are all possible side effects of intracavitary brachytherapy. Thromboembolic events are uncommon.

Estimates of the risk of late sequelae from radical radiation vary depending on the grading system, length of follow-up, calculation method, treatment approach, and prevalence of risk variables in the study group. Complication rates in individuals with extremely locally advanced pathologies may be greater due in part to tissue loss induced by infiltrative malignancy. Rectal complications are most frequent in the first 3 years after therapy and include bleeding, stricture, ulceration, and fistula. Small intestinal obstruction is a rare consequence of conventional radiation in patients with no additional risk factors. Patients with open transperitoneal lymph node dissection have a considerably higher risk of small intestinal blockage. A history of pelvic inflammatory disease or peritonitis, thin body habitus, heavy smoking, and the use of high doses or large volumes for external-beam irradiation, particularly with lowenergy treatment beams and large daily fraction sizes, can all increase the risk of small bowel complications in patients treated for cervical cancer [37].

High doses of radiation can produce persistent myelosuppressive effects and a lower tolerance to the effects of chemotherapy. These effects are caused when the microenvironment of the bone marrow is altered. Prospective analyses indicated a 25% prevalence of hematological damage >G3 when cisplatin-based chemoradiotherapy was utilized. Irradiating an expanded field that encompasses the para-aortic lymph node covering leads to greater irradiation of total bone marrow and, as a result, a higher incidence of hematological damage. This outcome must be examined and managed since it predisposes patients to infections, repeated hospitalizations, multiple transfusions, and delays in obtaining therapy [39, 40]. Loren K Mell reported about bone marrow-sparing IMRT in 2008. The report concluded that BMS-IMRT reduced the irradiation of pelvic bone marrow compared with the four-field box technique [41]. In order to find the most effective method to lessen the hematological toxicity associated with concurrent chemoradiotherapy (cCRT) for cervical cancer, De-Yang Yu and his colleagues set out to investigate the dosimetric characteristics of a variety of bone marrow-sparing strategies and radiation technologies in 2020. Their ultimate goal was to identify the most effective method. The scientists came to the conclusion that the IMRT plan that achieved the best sparing while still giving enough coverage of the target volume was the one that excluded the bone

marrow from the radiation treatment and treated the pelvic bones with discrete dosevolume limitations. In addition, among all of the more recent radiation treatment systems, the VMAT has shown itself to be the most successful in terms of preserving bone marrow while still providing overall efficacy. Patients with cervical cancer might benefit from this treatment technique since it can potentially lessen the hematological toxicity they experience. By using this method, we are able to increase the effectiveness of radiation and reduce the need for expensive functional imaging of active bone marrow [42].
