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Stronger Than Cancer Everything about cancer

Stage 1 lung cancer

by tang.weng.heng » 16 Feb 2017, 19:03

Mr A is an active 75-year-old retired veterinarian who enjoys travelling and hiking. Even though he has already retired from his practice, he still does not mind attending to sick animals that were brought to him occasionally by his friends and relatives.
Hence, when he discovered that his serum tumour marker CEA was on the high side, during a routine check-up, he was perplexed. He could eat and sleep well. He could jog and hike as well as someone half his age. Brushing it aside as probable laboratory error, he decided to sit on it and repeat the test again some time later. It remained elevated.
Serum CEA (carcinoembryonic antigen) is a blood test, usually done for surveillance and to assess treatment response in colorectal cancer. However, it may also be elevated in a number of other conditions.
​His children were concerned when they get to know about it. They persuaded their father to undergo further investigations. They certainly hope their fit, loving father would remain so for many years to come.
Mr A eventually underwent OGDS (oesophageal gastroduodenoscopy), an endoscopic examination of food pipe (oesophagus), stomach and upper part of small bowel (duodenum) as well as colonoscopy (endoscopic examination of colon and rectum). The results were normal, yet his CEA continues to rise.
​To further investigate, Mr A did PET-CT scan. Positron emission tomography-computed tomography (PET-CT) combines the functional information from PET with the structural localisation of CT.
​He was found to have a metabolically active lung nodule at his left upper lobe on the PET-CT. Fortunately, the disease has not spread to the lymph nodes, his right lung as well as other organs such as liver, adrenal, bone and brain. A subsequent CT-guided lung biopsy confirmed the lung nodule to be malignant (precisely a type of lung cancer known as adenocarcinoma, EGFR mutation positive, exon 21 L858R).
​Mr A is an ex-smoker, with mild degree of smoking-related chronic lung disease (COPD). He had also undergone balloon angioplasty and stenting for multiple heart vessel blockage three years earlier. Mr A takes blood thinning medication, clopidogrel, for prevention of heart attack.
Until a few years ago, surgery, in the form of lobectomy (removal of an entire lobe of lung) was the ‘gold standard’ for stage I lung cancer. However with the advancement in radiotherapy technique and delivery, there is a new treatment option, in the form of stereotactic ablative body radiotherapy (SABR) that gives much hope for patients with stage I disease like Mr A.
Mr A had a very thorough discussion with his oncologist on stage I lung cancer, the available treatment options, possible outcome and potential side effects. Considering his age and heart condition, surgery would pose a higher risk with prolonged recovery period. Mr A thus made an informed decision to be treated by a non-surgical approach.
Prior to the treatment, Mr A underwent 4D CT simulation, during which images of his lung tumour were taken over all phases of breathing. During the radiotherapy treatment planning process, an internal target volume (ITV) of the lung tumour was delineated based on the maximal intensity projection (MIP) from the 4D CT.
SABR, also known as stereotactic body radiotherapy (SBRT), refers to the precise delivery of radiation in several sessions (usually 3-5), instead of the conventional 20 to 30 sessions, with the aim of ablating the tumour. It combines the advantage of radiotherapy precision, as in Gamma Knife radiosurgery, with the radiobiological advantage of fractionated radiotherapy.
During cell cycle, tumour cells are more vulnerable during DNA synthesis phase. Meanwhile, oxygen-deprived tumour cells during the resting phase are relatively resistant. By delivering the radiotherapy over several fractions (or sessions), thereby irradiating the tumour in various phases of cell cycle, oncologists are able to exploit the relative vulnerability of tumour cells.
For patients like Mr A, who travel from his home country for treatment, treatment over several fractions is logistically more convenient and reduces overall treatment time. More importantly, SABR has been proven to be more effective than conventional radiotherapy. Various publications have confirmed the safety and efficacy of SABR, in comparison to other forms of treatments.
Mr A was able to continue with his life saving blood-thinning medication throughout the SABR process. Prior to every session, verification process with on-board kilovoltage cone-beam CT (CBCT) was done to ensure accuracy. Online registration of CBCT and 4D CT simulation images was done to identify set-up variation, with real time correction being made accordingly.
Mr A completed five sessions of SABR, done alternate day on out-patient basis over a week and a half. He was able to fly home in the same evening following the last session of treatment and tend to the animals that require his attention.
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