LUNG CAN­CER

The Gulf Today - Time Out - - TRAVEL - Dr Asheesh Me­hta In­ter­nal Medicine Spe­cial­ist

Lung can­cer is the sec­ond commonest can­cer. All can­cers taken to­gether cause about 9.6 mil­lion deaths an­nu­ally with lung can­cer alone ac­count­ing for 1.76 mil­lion deaths. The du­bi­ous dis­tinc­tion of be­ing by far the lead­ing cause of can­cer re­lated deaths in both men and women is rea­son enough to cre­ate greater aware­ness of the dis­ease. Lung can­cer is re­spon­si­ble for more deaths than can­cers of the breast, prostate and colon com­bined. When one con­sid­ers that the ma­jor­ity of lung can­cer cases are pre­ventable, this is all the more rel­e­vant. Novem­ber is ob­served as Lung Can­cer Aware­ness Month with a large num­ber of health or­gan­i­sa­tions and vol­un­teer or­gan­i­sa­tions par­tic­i­pat­ing.

A can­cer or car­ci­noma is un­re­strained and un­reg­u­lated growth of ab­nor­mal cells any­where in our body. Un­con­trolled growth of can­cer cells is at the cost of nor­mal cells. Can­cer cells cause symp­toms be­cause of lo­cal dam­age at the area of ori­gin and these cells also spread to con­tigu­ous or­gans and by the blood stream and lym­phat­ics to dis­tant sites. Can­cer le­sions in lo­ca­tions dis­tant from the site of ori­gin are called sec­on­daries or metas­tases. As far as lung can­cer is con­cerned there are two main types, de­pend­ing on the type of cells mak­ing up the can­cer. The com­moner one is called non-small cell lung can­cer (NSCLC) and is the type in about 85% of lung can­cer cases. The other one is small cell lung can­cer (SCLC). The lung is also a pref­er­en­tial site for se­condary can­cer from many dis­tant sites such as the breast, colon, stom­ach, etc. How­ever, metastatic can­cers in the lung are con­sid­ered as part of the orig­i­nal can­cer rather than as a true lung can­cer. NSCLC is fur­ther classiied into dif­fer­ent types de­pend­ing on the ap­pear­ance of the cells when in­spected un­der a mi­cro­scope af­ter ap­pro­pri­ate stain­ing. Types in­clude ade­no­car­ci­noma, squa­mous cell car­ci­noma and large cell car­ci­noma. Ade­no­car­ci­noma is the com­moner type com­pris­ing about 40% of all lung can­cer cases while squa­mous cell car­ci­noma makes up about 30% of cases. SCLC, although mak­ing up only about 15% of cases, is noted for its ag­gres­sive be­hav­ior with rapid dis­tant spread and gen­er­ally much worse prog­no­sis. Other types of can­cers in the lung such as car­ci­noid tu­mour are rel­a­tively rare.

The sin­gle most im­por­tant cause of lung can­cer is smok­ing. About 90% of lung can­cers are at­trib­uted to smok­ing, whether ac­tive or pas­sive. Risk of lung can­cer from smok­ing rises with the quan­tum as well as du­ra­tion. Cig­a­rette smok­ing has the high­est risk but other modes of smok­ing such as ci­gar and pipe smok­ing too im­part a sub­stan­tial risk. In fact, sec­ond hand smoke too is dan­ger­ous. Although the in­creased risk of lung can­cer starts re­duc­ing on quit­ting smok­ing it takes about 15 years for the risk to be near what it is for a non­smoker. Air pol­lu­tion is an­other im­por­tant risk fac­tor act­ing in a some­what sim­i­lar man­ner to smok­ing by in­hala­tion of nox­ious can­cer caus­ing chem­i­cals. Among other causes of lung can­cer are ex­po­sure to in­dus­trial prod­ucts or min­er­als with as­bestos be­ing the most well es­tab­lished as­so­ci­a­tion. Smok­ing in a per­son with as­bestos dis­ease of the lung in­creases the risk for lung can­cer ex­po­nen­tially. As­bestos has been re­placed with safer ma­te­ri­als in most ap­pli­ca­tions and work­ers in this in­dus­try are also bet­ter pro­tected and mon­i­tored much more closely than used to be the case in ear­lier times. Ex­po­sure to sil­i­con dust too may en­hance risk for lung can­cer. Ex­po­sure to radon gas is an­other im­por­tant con­trib­u­tory fac­tor. Radon is an in­ert gas gen­er­ated as a de­cay prod­uct of ura­nium. Radon it­self de­cays rapidly with emis­sion of harm­ful ioniz­ing ra­di­a­tions. Radon ex­po­sure gen­er­ally oc­curs due to in­her­ent ra­dioac­tiv­ity in the soil in a par­tic­u­lar area. Since the gas is odour­less and colour­less we can­not de­tect its pres­ence ex­cept with speciic equip­ment. The US En­vi­ron­men­tal Pro­tec­tion Agency es­ti­mates that about 1 in 15 homes in the USA con­tains dan­ger­ous lev­els of radon. Radon con­trib­utes to about 10% of all lung can­cer cau­sa­tion.

Symp­toms typ­i­cally arise late in cases of lung can­cer. In fact, in quite a few in­di­vid­u­als with lung can­cer there are no symp­toms at the time of di­ag­no­sis, the tu­mour hav­ing been de­tected dur­ing in­ci­den­tal or screen­ing x-ray of the chest. Symp­toms may in­clude per­sis­tent cough, breath­less­ness and chest pain. Any new on­set cough or wors­en­ing of an ex­ist­ing cough which per­sists more than a week or two, es­pe­cially in smok­ers, mer­its at­ten­tion. Should the cough be as­so­ci­ated with bloody spu­tum it has even more omi­nous sig­ni­icance. While most such coughs turn out to be due to more in­nocu­ous prob­lems such as pharyn­gi­tis or bron­chi­tis, a per­sis­tent cough needs in­ves­ti­ga­tion to rule out lung can­cer. Chest pain may be com­plained of dur­ing cough­ing or apart from the cough. Breath­less­ness on ex­er­tion or even at rest may be present and may sig­nify prob­lems like col­lec­tion of luid in the pleu­ral cav­ity around the lung or the can­cer ob­struct­ing low of air into part of the lung. Other com­plaints in­clude un­ex­plained loss of ap­petite and weight and ex­ces­sive fa­tigue. Spread to dis­tant sites may be the irst in­ti­ma­tion of lung can­cer. Symp­toms in this case de­pend on the site of spread and the sever­ity of le­sion. The bones are often the site of sec­on­daries from lung can­cer with com­mon sites be­ing the spine, the thigh bones, pelvis and ribs and may present with bone pains at these sites. The liver and brain are other com­mon sites for lung can­cer to spread. In some peo­ple with lung can­cer symp­toms at­trib­ut­able to what are called para­ne­o­plas­tic syn­drome oc­cur. Un­usual symp­toms not due to the mass ef­fect of the tu­mour or to dis­tant spread oc­cur. For in­stance, serum cal­cium lev­els may be el­e­vated or thy­roid hor­mone lev­els may be high or there may be symp­toms sug­ges­tive of nerve de­gen­er­a­tion. Some of these syn­dromes are due to aber­rant pro­duc­tion of chem­i­cals by the tu­mour while in oth­ers the mech­a­nism of symp­toms is not clear. The un­der­ly­ing cause for these atyp­i­cal symp­toms is eas­ily over­looked by the un­wary physi­cian till late.

For di­ag­no­sis of lung can­cer, x-ray chest is quite help­ful as a screen­ing tool. CT scan and MRI are more sen­si­tive imag­ing tests. Bron­choscopy in­volves pas­sage of a thin en­do­scope into the larger air pas­sages through the nose or the mouth and in­spect­ing the im­age on a video mon­i­tor or through the eye­piece. Tis­sue sam­ples can also be col­lected for cy­to­log­i­cal ex­am­i­na­tion for can­cer. The spu­tum can also be eval­u­ated for can­cer cells but the yield is less sat­is­fac­tory. Biopsy to ob­tain tis­sue for mi­cro­scopic ex­am­i­na­tion can also be car­ried out by a nee­dle in­tro­duced through the skin or by spe­cial tests such as me­di­astinoscopy or even by surgery; the se­lec­tion of route de­pends on the lo­ca­tion and other char­ac­ter­is­tics of the le­sion as seen on x-ray and other imag­ing tests. Conir­ma­tion of can­cer di­ag­no­sis by cy­tol­ogy or histopathol­ogy is of ob­vi­ous im­por­tance in plan­ning treat­ment. In­ves­ti­ga­tions are also re­quired to de­tect if the can­cer re­mains lo­cal­ized to the lung or has spread to con­tigu­ous ar­eas or dis­tant sites.

Treat­ment de­pends on the stage and whether it is of NSCLC or SCLC type. Stage 1 is a small can­cer that is lo­cal­ized to the site of ori­gin while stage 4 can­cer refers to one that has spread to dis­tant sites. The no­to­ri­ously poor prog­no­sis of lung can­cer is largely due to most can­cers be­ing de­tected late in the course of the dis­ease. The 5 year sur­vival for a stage 4 lung can­cer is less than 5% while those with dis­ease with­out dis­tant spread have about a 50% sur­vival rate. Surgery to re­move re­sectable can­cers along with chemo­ther­apy and ra­di­a­tion to pre­vent re­cur­rence are the stan­dard con­ven­tional modes of lung can­cer ther­apy. If surgery is not pos­si­ble chemo­ther­apy and / or ra­dio­ther­apy may of­fer pal­li­a­tion. Surgery is rarely pos­si­ble in SCLC be­cause rapid spread of this type of can­cer means that metas­tases are al­ready present in most cases at the time of di­ag­no­sis. Tar­geted ther­apy is an­other op­tion in se­lected cases. These are agents that are ef­fec­tive when speciic mu­ta­tions are present in can­cer cells. Test­ing for these mu­ta­tions is done at ini­tial di­ag­no­sis. A very large num­ber of dif­fer­ent mol­e­cules have been used in tar­geted ther­apy. This type of ther­apy is still evolv­ing at a fast pace and hope­fully at least some types of lung can­cers will show good re­sponse. Cur­rently the prog­no­sis for most lung can­cers re­mains bleak. In­creas­ing aware­ness of the harm­ful ef­fects of smok­ing in all forms and of the need for early di­ag­no­sis and early treat­ment thus be­comes all the more im­por­tant to im­prove the out­come.

The sin­gle most im­por­tant cause of lung can­cer is smok­ing. About 90% of lung can­cers are at­trib­uted to smok­ing, whether ac­tive or pas­sive

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