Small cell lung cancer (SCLC) accounts for 20% to 30% of all lung cancers. It is highly malignant, rapidly progressive, prone to early metastasis, and often ineffective with targeted drugs, and currently relies heavily on radiation and chemotherapy. However, if you have SCLC, don’t be discouraged, there are more and more ways to deal with it.
On January 17, 2018, the National Comprehensive Cancer Network (NCCN) released new guidelines for SCLC. There are some new approaches and new ideas about radiation therapy, which we’ve sorted out for you below.
I. Use newer radiotherapy techniques that increase the radiation dose to the tumor while protecting surrounding normal tissue.
New technologies include:
1. 4D-CT (Four Dimensional Computed Tomography). 4D-CT incorporates the “time” factor into the image scanning and reconstruction process to better reflect the characteristics of internal organs as they change with respiration. For example, lung tumors are significantly displaced during respiration, and in conventional radiotherapy, a large border around the target area is often expanded to compensate for this effect, resulting in radiation exposure to surrounding normal tissue. In contrast, 4D-CT images can track the motion of the lung tumor during the respiratory cycle and accurately compensate for the effect of motion when the target area is outlined, allowing for more precise irradiation coverage.
2. PET-CT simulation. It improves the accuracy of radiotherapy coverage. Before radiotherapy, the tumor invasion site and the area to be irradiated must first be precisely outlined. The use of PET-CT fulfills the requirement for precise target area setting for precise radiotherapy.
3. Intensity-modulated radiation therapy (IMRT) IMRT evolved from 3-dimensional conformal radiation therapy (3D-CRT). It is based on 3D-CRT, which can satisfy two conditions simultaneously: 1). In the direction of irradiation, the radiation field is consistent with the shape of the target area; 2). The dose is equal everywhere in the target area and on the surface of the target area and can be adjusted as needed.
4. Volumetric Modulated Arc Therapy (VMAT), which rotates the tumor at any angle within a 360° single- or multi-arc setting, provides greater range, flexibility, and precision than conventional radiotherapy, and can shorten the entire treatment process to 3-6 minutes.
5. Image-guided radiation therapy (IGRT). IGRT ensures that the target is in the same place for every treatment and that treatment is fully synchronized with breathing.
II. Limited-stage SCLC
1. The optimal dose and duration of radiation therapy is unclear. 45 Gy/3 weeks (1.5 Gy twice daily) is superior to the 45 Gy/5 weeks (1.8 Gy once daily) regimen.
Note: Gy, also known as “gore”, is a unit of radiation therapy dose.
2. The previous version of the guidelines recommended surgery for early-stage patients with pathologically confirmed non-invasive mediastinal lymph nodes, but postoperative adjuvant chemotherapy, usually 4 cycles, is required. So, do you need radiotherapy after surgery? The new guidelines state:
Postoperative pathology suggests N1 (tumor invasion of the ipsilateral peribronchial lymph nodes, intrapulmonary lymph nodes, or hilar lymph nodes), and postoperative mediastinal radiotherapy may or may not be done.
Postoperative pathology suggests N2 (tumor invades ipsilateral mediastinal lymph nodes or subglottic lymph nodes), which requires postoperative mediastinal radiotherapy.
3. If pre-chemotherapy is effective and the disease is in complete or partial remission, prophylactic brain irradiation is recommended to reduce intracranial metastases and prolong survival.
Note: Complete remission is defined as disappearance of all target lesions, no new lesions, normal tumor marker levels, and maintenance for more than 4 weeks; partial remission is defined as tumor shrinkage of more than 30% and maintenance for more than 4 weeks.
III. Extensive stage SCLC
1. After achieving remission with systemic chemotherapy, physicians may give chest consolidation radiotherapy to appropriate patients.
The population that would benefit from consolidation chest radiotherapy is likely to be primarily those patients who have residual disease in the chest after chemotherapy.
2. After effective control by systemic chemotherapy, prophylactic brain irradiation can reduce the occurrence of brain metastases.
When doing prophylactic brain irradiation, consider using memantine (a drug for Alzheimer’s disease) at the time of and after radiation therapy to help reduce neurocognitive impairment from whole-brain radiation therapy.
If you do not receive prophylactic brain radiation, you will need to have regular brain exams.
3. If brain metastases have occurred, whole-brain radiation therapy should be received rather than stereotactic radiation alone, because brain metastases are often multiple.
To summarize, the new US guidelines on radiotherapy for SCLC convey some new advances and ideas, but the US guidelines are based on US realities and some are not appropriate for our patients. However, the US guidelines are based on the actual situation in the US and some of them are not suitable for our patients. Therefore, this article is not a substitute for your doctor’s opinion, and you should follow your doctor’s instructions regarding your specific condition.
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