NEWS & PERSPECTIVE

IG-IMRT as a more favorable adjuvant radiation alternative for hysterectomized cervical cancer patients

31 Dec 2020

Radiotherapy as adjuvant treatment after total hysterectomy has proven to be effective in lowering cancer-specific mortality rate.1 However, traditional three-dimensional conformal radiotherapy (3D-CRT) as adjuvant treatment after total hysterectomy is associated with a series of late gastrointestinal toxicity, ranging from diarrhea, abdominal bloating, bowel obstruction to anorexia.2 Recently, researchers in India have replaced 3D-CRT with another type of radiotherapy, an image-guided intensity-modulated radiotherapy (IG-IMRT), and showed that IG-IMRT can reduce the risk of late gastrointestinal toxicity while delivering similar efficacy when compared to 3D-CRT.2 This article summarizes a recent study that compared the safety and efficacy of 3D-CRT and IG-IMRT as adjuvant treatment options among postoperative high-risk cervical cancer patients.

Total hysterectomy is a treatment option for women with high-risk cervical cancer by removing cancerous tissues and cells, with 5-year progression-free and overall survival rates of over 60% approximately.2,3 However, some patients may experience disease recurrence after total hysterectomy.1 Indeed, a study has shown that patients with grade 3 tumor larger than 2cm and previous lymphovascular space invasion (LVSI) have a greater predicted risk of cancer recurrence at more than 40%, whereas the risk is only less than 5% in those without LVSI.1,4 To prevent cancer recurrence and to improve patient survival, adjuvant radiotherapy can be offered to improve the 5-year survival rate of post-hysterectomy cervical cancer patients from 50.3% to 68.0% (p=0.029).5 However, radiotherapy such as 3D-CRT is also associated with late gastrointestinal toxicity which may jeopardize a patient’s quality of life.2 According to the PARCER study, which was a phase 3, randomized, 49-month trial, among the 149 patients aged 18-65 years old who had received 3D-CRT as adjuvant treatment, 36.2% and 8.7% of whom had suffered from ≥grade 2 and ≥grade 3 late bowel toxicity, respectively, with another 27.2% experienced ≥grade 2 acute diarrhea.2

To address the potential bowel toxicities of 3D-CRT, IG-IMRT was introduced as a potentially safer alternative radiotherapy option.2 The PARCER study revealed that IG-IMRT, when compared to 3D-CRT, had demonstrated a lower risk of ≥grade (19.2% vs. 36.2%, HR=0.53; 95% CI: 0.33-0.83; p=0.005) and ≥grade 3 late bowel toxicity (2.0% vs. 8.7%, HR=0.23; 95% CI: 0.06-0.81; p<0.01), as well as a lower risk of ≥grade 2 acute diarrhoea (17.2% vs. 27.2%, p<0.004).2 In terms of efficacy, IG-IMRT had shown a comparable disease-free survival rate at 73%, when compared to the 68% in 3D-CRT (p=0.30).2 Given a comparable efficacy and superior safety profile, IG-IMRT may have the potential to replace 3D-CRT as the standard adjuvant radiotherapy in the postoperative treatment setting.2

By implementing IG-IMRT, the risk of adverse events associated with radiotherapy can be greatly reduced to improve high-risk cervical cancer patients’ quality of life. To avoid unexpected incidences, more extension studies would be required to fully understand the long-term effects of IG-IMRT as adjuvant treatment in total hysterectomized patients before the full replacement of 3D-CRT. Summarizing the efficacy and safety of IG-IMRT from the PARCER study, Dr. Sue Yom, University of California, San Francisco, concluded that, “I see [IG-IMRT] as having potentially important future impacts on clinical practice.”


References
  1. Eifel PJ. The value of pelvic radiation therapy after hysterectomy for early endometrial cancer. Oncology. 2013;27(10):990-999.
  2. Chopra S et al. Phase III Randomized Trial of Postoperative Adjuvant Conventional Radiation (3DCRT) versus Image Guided Intensity Modulated Radiotherapy (IG-IMRT) in Cervical Cancer (PARCER): Final Analysis. Int J Radiat Oncol Biol Phys. 2020;108(3):S1-2.
  3. Agarwal S et al. Outcomes of patients undergoing radical hysterectomy for cervical cancer of high-risk histological subtypes. Int J Gynecol Cancer. 2011;21(1):123–127.
  4. Akhavan S et al. The impact of lymphovascular space invasion on recurrence and survival in Iranian patients with early stage endometrial cancer. World J Oncol Res. 2016;7(4):70-74.
  5. Diavolitsis V et al. The role of adjuvant radiation in endometrial cancer. Oncology. 2009;23(4):342–349
RADIOTHERAPY
HYSTERECTOMY
THREE-DIMENSIONAL CONFORMAL RADIOTHERAPY
3D-CRT
IMAGE-GUIDED INTENSITY-MODULATED RADIOTHERAPY
IG-IMRT