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Curative Radiation Treatment of lung cancer


Medical editor Odd Terje Brustugun MD
Oncologist

Oslo University Hospital
Norway

General

Non-small cell lung cancer

Patients unfit for surgery, or not willing to undergo a surgical procedure, will be offered curatively intended radiation therapy. In stage I, this will be given as stereotactic radiation, with a high radiation dose in few fractions. In stage II or III, fractionated therapy given over several weeks is offered, either alone or in combination with chemotherapy.

Many patients with clinically localized cancer (stage III) have subclinical micrometastases and this group of patients is given systemic chemotherapy simultaneously with curative radiation therapy.

Combinations

  • Induction chemotherapy of 2-3 courses before radiation treatment 
  • Chemotherapy given in parallel with curative radiation therapy as a radiation sensitizer (concomitant treatment)
  • A combination of the above alternatives
  • Adjuvant chemotherapy after concluded curative radiation therapy

There is no evidence for a benefit from routinely postoperative radiation therapy.

Each additional treatment of curative radiation doses causes increased side effects. Internationally, concomitant chemoradiation treatment is recommended. Patients who are not suitable for inclusion of a protocol study, but who still meet the prognostic factors which indicate a curative treatment arrangement, are given radiation alone in doses of 60–74 Gy. 

Stereotactic radiation is first-line treatment of choice for medically inoperable stage I patients.

Small cell lung cancer

Radiation therapy given in addition to chemotherapy provides a survival benefit. Radiation should commence early in the treatment course. 

Indications

Non-small cell lung cancer

  • Stage I and II with good prognostic factors and considered surgically inoperable, or surgery not wanted.  
  • Stage IIIA with good prognostic factors and considered inoperable or inappropriate for neoadjuvant chemotherapy.
  • For stage IIIB, curative radiation treatment is possible if the patient has good prognostic factors.

Small cell lung cancer

  • Localized cancer, stage I–III 

Goal

  • Cure the disease

Definitions

The tumor, including pathologically enlarged lymph nodes in the ipsilateral hilum and mediastinum define the target volume (GTV). Margins of 1.5–2 cm are used to compensate for microscopic spreading, tumor movement with respiration, and tuning variations (CTV, PTV). The volume of risk organs in the radiation field such as the medulla, heart, and healthy lung, must be minimized according to the maximum tolerable dosage.

Target Volume

 

 

Target volume definitions from ICRU
(International Commission on Radiation Units and Measurements)

GTV (= Gross Tumor Volume)

Tumor volume

Palpable or visible/demonstrative area of malignant growth. 

CTV (= Clinical Target Volume)

Clinical target volume

Tissue volume which contains GTV and/or subclinical microscopic malignancy.

ITV (= Internal Target Volume)

Target volume

Volume containing CTV and a inner margin taking into account inner movements and revisions of CTV.

PTV (= Planning Target Volume)

Planning volume

Geometric volume containing ITV and a Setup margin taking into account assumed variations for patient movements, variations in patient arrangement, and field modeling.

 


Preparation

Target volume and radiation technique

The radiation fields are formed based on the CT images  .

  • The patient meets for imaging on a dedicated CT machine, with or without contrast.
  • The localization of the tumor and risk areas are drawn directly into the images and create a 3D radiation volume. 
  • Radiation therapists suggests a radiation field set-up which is eventually adjusted and approved by a medical physicist and the treating doctor. Ideally, there should be a uniform dose distribution over the target volume and no radiation to critical organs. In reality, this is impossible to achieve. The dose distribution is therefore a compromise between what is desired and what is possible.
  • During a CT scan, it is very important that the patient is well medicated for pain and is able to lie still on their back when the images are taken. If necessary, a premedication is given or extra dose of opiates for those who are taking them.
  • The patient lies flat on a bench with only a thin mattress.
  • An abdominal pressure can be applied during stereotactic radiation to minimize diaphragm-caused respiratory movements. 

Implementation

Non-small cell lung cancer

  • Stage I – The radiation field is limited to only include the tumor (GTV) and margins (CTV + PTV) without the hilum and mediastinum. A 3D CT-based dosage plan is prepared. The treatment is given over 3 fractions of 15 Gy or 8 fractions of 7 Gy. This treatment takes 2-3 weeks including planning. Alternatively 2 Gy x 30–37 are given within 6-8 weeks.
  • Stage II – A larger radiation field using CT-based 3D dosage plan toward the tumor is applied, including pathologically enlarged lymph nodes (GTV), in addition to uncertainty and tuning margins (CTV + PTV). Schedules of 2 Gy x 30–35 are given. Adjuvant chemotherapy is usually given.
  • Stage IIIA/B – Radiation treatment is given using a CT-based 3D dosage plan with the same technique and dose as in stage II. Treatments are fractioned into 2 Gy x 30–33. Concomitant chemotherapy is usually given

Postoperative treatment

After surgery, radiation therapy is appropriate under the following circumstances:

  • For N2 cancer after lung surgery (pN2), postoperative radiotherapy should be given. CT-based 3D dosage planning technique to the mediastinum, 60 Gy with 2 Gy per daily fraction.
  • For involved histopathological margins (both R1 (microscopic) and R2 (macroscopic)) 50–60 Gy should be given, CT-based 3D dosage plan, 2 Gy per daily fraction.

For radically operated N0-1 cancer, there is no indication for postoperative radiation therapy.

Small cell lung cancer

Toward the tumor and mediastinum with margins, fractionated CT-dosage planned treatment is given e.g. 1,5 Gy twice daily, 30 fractions as a total dose (alternatively 2.8 Gy x 15 is given). Pathological lymph nodes observed with CT/PET before starting chemotherapy must be included in the radiation field. Early initiated radiation therapy gives a small, but significant survival benefit compared to a late start. Radiation should therefore be started no later than just after the second course of chemotherapy. The third course should not be postponed.

In case of partial or complete response upon evaluation at 4–6 weeks after the last course of chemotherapy, patients with small cell lung cancer should be offered prophylactic radiation therapy to the brain.


Follow-up

Patients should be monitored at 4–6 weeks after concluded curative radiation therapy (or the last chemotherapy course for small cell cancer), for side effects and evaluation for adjuvant chemotherapy.

Monitoring thereafter should be about every third month and include imaging with either thoracic X-ray or CT. The frequency of CT monitoring should be individualized, but not less than once a year for the first years.

Early reactions

Fatigue

Radiation therapy may render the patient more fatigued and lethargic. Reduced appetite, nausea, diarrhea, and pain lead to fatigue. The fatigue does not always disappear when treatment is ended. In outpatients, fatigue may also be caused by stressful transportation.

Skin reactions

Reactions in the skin from radiation are normal and worsen with increasing doses. Soreness may last and/or increase until at least a couple of weeks after treatment has finished. Intertriginous areas (for example under the breasts) are especially susceptible. Airing, salt water compresses, and perfume-free creams may help. Ointment and creams should not be applied to the radiation field for the last hours before each treatment session. 

Problems swallowing

Radiation treatment which includes larger or smaller parts of the mediastinum and neck, leads to irritation and soreness in the throat and esophagus, and subsequent swallowing problems. Diet advice, "lubrication" with cream or ice cream just before eating may help, otherwise, local analgesics or systemic pain medication will help. In rare cases, tube feeding is necessary.

Lung/respiratory symptoms

Swelling in the radiated tissue/mucosa can lead to temporary deterioration of breathing after the first treatments. Radiation-induced pnemonitis with fever can also occur. Steroid treatment may become necessary for this.

Late reactions

A late reaction to radiation treatment to the lungs may be reduced lung capacity.


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