Specialized Radiotherapy Treatment Better for Adenocarcinoma Type of Lung Cancer

Early stage lung cancer treatment for patients who cannot be operated showed better outcome with radiotherapy if they had adenocarcinoma type of cancer vs squamous cell cancer.

Highlights:

The effect of stereotactic body radiation therapy (SBRT) on different types of lung cancer was studied by scientists from the Cleveland Clinic.
Squamous cell carcinoma patients had two times the risk of local failure after SBRT when compared to patients with adenocarcinoma.
These findings can be used to optimize treatment for lung cancer patients based on the cells of origin.

Patients with early stage non-small cell lung cancer with squamous cell carcinoma who undergo Stereotactic Body Radiation Therapy (SBRT) have a higher rate of local failure when compared to other non-small cell lung cancer patients. This study conducted by a group of researchers from The Cleveland Clinic will help tailor treatment plans based on the type of lung cancer.

Lung Cancer

Lung cancer is the most common form of cancer and is the most common cause of cancer-related death in the world.

It accounts for 13% of all new cancer cases worldwide
It accounts for 19% of cancer-related death in the world
About 1.8 million new lung cancer patients were detected in 2012
Lung cancer constitutes 6.9% of all new cancer cases in India
It constitutes 9.3% of all cancer-related death in India
It is the most common form of cancer and cancer-related death among men
In India, Mizoram has the highest incidence of lung cancer

The two main types of lung cancer are

Non-Small Cell Lung Cancer (NSCL)- 80-85% of lung cancer falls under this category.
Small Cell Lung Cancer - constitutes 10-15% of lung cancer

NSCL are grouped into three subtypes based on their cells of origin.

Squamous cell carcinoma: It constitutes 25 to 30% of all lung cancers. They originate in squamous cells that are flat cells which are present in the inner lining of the airways of the cells. Smokers are known to get this type of cancer and include a main airway like bronchus.
Adenocarcinoma: It constitutes 40% of all lung cancers and are formed in cells that normally secrete mucous.
Large cell carcinoma: It constitutes 10 to 15% of all lung cancers. It could form in any part of the lung.

Treatment for Lung Cancer

Surgery is considered during the early stages of lung cancer (stage I and II). However, surgery may not be possible always and depends on -

Age of the patient
Medical co-morbidity
Location of the tumor

When surgery is not possible stereotactic body radiation therapy or SBRT is used as it is a non-invasive, high precision radiation delivery mechanism

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‘The use of stereotactic body radiation therapy (SBRT) optimized based on histological origins of cancer will provide greater benefits. Adenocarcinoma type of lung cancer have better outcome with radiotherapy.’

Impact of Histological Subtype and Tumor Heterogeneity on SBRT Treatment

Scientists from Cleveland Clinic, U.S, analyzed 740 patients who underwent SBRT during the period 2003 to 2015 to identify the impact of histological subtype and heterogeneity of the tumor on SBRT treatment outcomes.

The patients were grouped into 4 categories

Adenocarcinoma-32%
Squamous cell carcinoma-29%
Unknown- These included people who did not have a biopsy-30%
Non-small cell lung cancer-8%

The patients were balanced for age, radiation rate, sex, body mass index (BMI) and performance status. The analysis carried out by the scientists showed that squamous cell carcinoma, younger age, higher BMI, few medical co-morbidities, higher positron emission tomography (PET) and lower dose of radiation were associated with an increased risk of local failure.

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When multivariate analysis was used to calculate the strongest predictor of local failure, it was found that squamous cell carcinoma histological subtype was the strongest predictor at a rate that was significantly higher than people with adenocarcinomas.

This is one of the first studies that analyzed the effect of SBRT on histological sub-types of cancer, according to the authors. Squamous cell carcinomas had a higher rate of failure than other types of NSCLC. The study found that the local failure of squamous cell carcinoma was two fold higher than adenocarcinoma.

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Lung cancer can be diagnosed only in the advanced stages of the disease. Therefore, early screening is recommended for a better prognosis.

Stereotactic Body Radiation Therapy (SBRT)

SBRT is a radiation therapy that is used for tumors outside the central nervous system. In this treatment procedure, a specialized co-ordination system is used for the exact localization of the tumors in the body. Ether a single high dose radiation treatment is delivered or a few fractionated treatment procedures are administered.

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This form of therapy requires specialized beam of radiation delivered at different angles which requires special radiation oncologists to carry out the procedure.

SBRT is administered for those cancers that are not easily accessible or are present in underlying tissues. The current study evaluated the benefit of using SBRT on the different types of non-small cell lung cancer, which is the first study on the difference in outcome based on histological differences. The study found conclusively that adenocarcinomas had a two time lower risk of local failure when treated with SBRT when compared with squamous cell carcinoma.

The study can be used to optimize treatment for non-small cell lung cancer based on histological origins of the cancer.

References:

Lung cancer: Prevalent trends & emerging concepts - (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4405940/)
What Is Lung Cancer - Non-Small Cell? Topics - (http://www.cancer.org/cancer/lungcancer-non-smallcell/detailedguide/non-small-cell-lung-cancer-what-is-non-small-cell-lung-cancer)

Source-Medindia